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Established 1989 Fastener Handbook

Blacks Catalogue

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Page 1: Blacks Catalogue

Established1989

Fastener Handbook

BLACKS FASTENERS LTD

AUCKLAND930c Great South RoadT: (09) 589 1036 F: (09) 589 1037

NELSONCorner Brilliant Place and Nayland RoadT: (03) 547 5102 F: (03) 547 0189

CHRISTCHURCH39a Gasson Street, SydenhamT: (03) 365 2460 F: (03) 365 2464

CHRISTCHURCH521c Blenheim Road, SockburnT: (03) 348 0340 F: (03) 348 0346

INVERCARGILL156 Bond StreetT: (03) 214 4499 F: (03) 214 4489

Freephone: 0800 652 463 Freefax: 0800 652 464

www.blacksfasteners.co.nz

Page 2: Blacks Catalogue

FastenerHandbook

Bolt Products

This book has been published to help our customers choose the rightfasteners for the job. The majority of the information is based on AjaxSpurway Fasteners. The fasteners may vary slightly to othermanufacturers.

BLACKS FASTENERS LTD accepts no responsibility for any loss dueto this publication.

This publication is distributed on the basis and understanding that thepublisher is not responsible for the results of any actions being takenon the basis of information in this publication nor for any error in oromission from this publication.

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Page 3: Blacks Catalogue

F A S T E N E R S

Page No.

1 Headmarks (Bolts)

2 Standard Bolt Product Range

3-4 Thread Forms and Fits

5-6 Testing of Bolts and Nuts

7 Strength-grade Designations for Amercian andBritish Standard Fasteners

8-13 Breaking and Yield Loads

14-15 Bolt Shear Capacity

16-20 Design of Bolted Joints for General Engineering

21-30 Tightening of Bolted Joints

31-35 Tightening of Structural Bolts

36-44 Structural Design using Black's Bolts

45-48 Black's Structural Bolts

49 Black's High Strength Structural Bolts

50-51 Coronet Load Indicators

52 High Tensile Hexagon Bolts

53 Hexagon Head Set Screws

54-55 Metric Hexagon Bolts and Set Screws

56-57 Hexagon Head Bolts

58-59 Cup Head Square Neck Bolts

60 Coach Screws

61 Elevator Bolts Four Peg

62-63 Metric Hexagon Nuts

64 Hexagon Nuts and Hexagon Lock Nuts

65 Nyloc Nuts Metric

66 Nyloc Nuts BSW

67 Nyloc Nuts UNC/UNF

68 Correct Use of Jam or Lock Nuts

69-74 Corrosion Protective Coatings

75-76 Tapping Drill Tables

77 Thread Screw Pitches

78-80 Hardness Conversion Table

81 The Torquing of Stainless Steel

82-83 Mechnical Properties of Stainless

84 Material Compatibility

Index

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1

HeadmarksF A S T E N E R S

Fasteners your guarantee of quality industrial fastenersFasteners your guarantee of quality industrial fasteners

A manufacturer’s brand, usually aletter or symbol on the head ofeach fastener is mandatory forcompliance with the relevant NewZealand Standard.

The following table indicates theBlacks Fasteners range of stockedbolt products which comply toAustralian standards.

• Mechanical properties• Chemical composition• Source of manufacture –

“Manufacturer’s Identification”.

Head Marking Bolt Type New Zealand Standard

Hexagon Head AS 1111

Metric Commercial

Hexagon Head AS 2451

BSW Mild Steel

Hexagon Head Precision AS 1110-8.8 metric

Metric High Tensile Grade 5 Imperial

Hexagon Head AS 2465

Unified High Tensile (UNC/UNF) (SAE) Grade 8

Hexagon Head High Strength AS 1252

Structural

Cup Head BSW AS 1390

Square Neck

Cup Head Oval Neck Fishbolts AS 1085

Cup Head BSW AS B108

Square Neck

Cup Head Oval Neck Fishbolts (AS E25)

Hexagon Head AS 1393

Metric Coach Screws

M

FJ

8.8

M

M

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Fasteners your guarantee of quality industrial fasteners

Standard Bolt Product Range F A S T E N E R S

Table 1 Standard Standard AustralianRange Range Standard

Product Bolt & Nut Bolt only

ISO Metric Threads

Commercial Hexagon Head Bolts B G Z AS 1111

Commercial Hexagon Head Set Screws B G Z AS 1111

Cup Head B G Z AS 1390

Cup Head Oval Neck Fishbolts B AS 1085

Precision Hexagon Head High TensileBolt Property Class 8.8 B Z B AS 1110

Precision Hexagon Head High TensileSet Screws Property Class 8.8 B Z AS 1110

Precision Hexagon Head High TensileFine Thread Bolts Z

Precision Hexagon Head High TensileFine Thread Set Screws Z

High Strength Structural BoltsProperty Class 8.8 B G AS 1252

Hexagon Head Coach Screws G Z AS 1393

BSW Threads

Mild Steel Hexagon Head Bolts B G Z AS 2451

Mild Steel Hexagon Head Set Screws BGZ AS 2451

Cup Head BZ AS B108

Cup Head Oval Neck - Fish Bolt B (AS E25)

Four Peg - Elevator Bolts B

UNC Threads

High Tensile Hexagon Head BoltsGrade 5 B Z B AS 2465

High Tensile Hexagon Head Set ScrewsGrade 5 B Z AS 2465

High Tensile Hexagon Head BoltsGrade 8 B Z B AS 2465

High Tensile Hexagon Head Set ScrewsGrade 8 B Z AS 2465

UNF Threads

High Tensile Hexagon Head BoltsGrade 5 B Z B AS 2465

High Tensile Hexagon Head Set ScrewsGrade 5 B Z AS 2465

High Tensile Hexagon Head BoltsGrade 8 B Z B AS 2465

High Tensile Hexagon Head Set ScrewsGrade 8 B Z AS 2465

NOTES:1) Restricted range for some products. Check availability of particular sizes.2) B = Plain finish 3) G = Galvanised finish to AS 1214 4) Z = Zinc Plated finish to AS 1897

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3

Threads Forms & FitsF A S T E N E R S

Fasteners your guarantee of quality industrial fasteners

All standard Blacks screws aremade in accordance with the latestissues of the thread specificationsshown in Table 2. Otherdimensional features conform withthe specifications listed in Table 1.

Standard products, unlessspecifically requested, aremanufactured to the Australianstandard (AS) specifications whichare designed to ensureinterchangeability withcorresponding International (ISO)American (ANSI/ASME) andBritish (BS) standards.

Table 2 Thread SpecificationsScrew thread system Specification Title

British Standard AS 3501 Parallel Screw Threads ofWhitworth B.S.W. Whitworth Form

Unified NationalFineUNF AS 3635 Unified Screw Threads

Unified NationalCoarseUNC

ISO Metric AS 1275 Metric Screw Threads forCoarse Pitch Series Fasteners

ISO Metric AS 1721 General Purpose MetricFine Pitch Series Screw Threads

Screw Thread Terminology

Standard Thread Forms FIGURE 1 FIGURE 2

FIGURE 3 FIGURE 4

FIGURE 5 FIGURE 6

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Fasteners your guarantee of quality industrial fasteners

Threads Forms & Fits F A S T E N E R S

Thread Fits

Screw thread standards providefor various classes of fit using ahole basis tolerancing system (iemaximum metal limit of theinternal thread is basic size),allowances for fit being applied tothe external (bolt) thread.

Exception is made for galvanisedfasteners where an additional

allowance is made in the nut(which is tapped after galvanising)to accommodate the thick coatingon the male thread. OnlyFree/1A/8g and Medium/2A/6gthreads should be galvanised.

Table 3 consists of the three threadclass combinations which apply tothe majority of commericalapplications.

Table 3

Thread class

Whitworth United Application(BSW & (UNC & ISOBSF) UNF) Metric

Applies to the majority of nuts andBolt Free 1A 8g bolts of ordinary commericalNut Normal 1B 7H quality. The clearance permits

rapid assembly without excessiveplay.

Bolt Medium 2A 6g Represents a precision qualityNut Normal 2B 6H screw thread product.

An exceptionally high gradeBolt Close 3A 4h threaded product, recommendedNut Medium 3B 5H only for applications where a close

snug fit is essential. (See note.)

NOTE: These higher classes do not make any allowance for fit (ie maximum boltsand minimum nuts have a common size) and under some circumstancesselective assembly may be necessary.

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5

Testing of Bolts & NutsF A S T E N E R S

Fasteners your guarantee of quality industrial fasteners

The normal tensile properties ofmetals; tensile strength, proofstress, 0.2% yield stress,elongation, reduction of area; aredetermined on machined testpieces. While these propertiesand testing methods can beapplied to bolt materials, it is theusual practice to test bolts intheir full size to more adequatelyreproduce the conditions underwhich they will be used in service.

This procedure of tensile testingbolts in their full size is recognisedand adopted by manystandardising bodies, including theInternational Organisation forStandardisation (ISO), BritishStandards Institution, StandardsAssociation of Australia, AmericanSociety for Testing and Materials(ASTM) and Society of AutomotiveEngineers (SAE).

The bolt is screwed into a tappedattachment (Figure 7) with six fullthreads exposed between the faceof the attachment and theunthreaded shank. The bolt head isinitially supported on a parallelcollar for the proof load test, and atapered or wedge collar for thesecond stage when it is broken intension.

In this test, the bolt load iscalculated from the tensile strengthof the material, and the TensileStress Area of the thread. TheTensile Stress Area is the areacalculated from the mean of theminor and pitch diameters of thethread. Tensile Stress Areas forcommon sizes and thread formswill be found in Tables 5-11.

The test, as indicated above, iscarried out in two stages:

(1) Proof Load Test. Thisconsists of applying a proof load(derived from a “proof load” stress)with the bolt head supported on aparallel collar. The bolt length ismeasured accurately before andafter application of the proof load.It is required that the bolt shall nothave permanently extended. A0.0005” or 12.5 micrometersallowance is made for errors ofmeasurements. This test provides aguide to the load to which the boltwill behave elastically.

(2) Wedge Tensile Test. Thebolt is assembled as describedpreviously but with the headsupported on a tapered wedgecollar. The angle of the wedge isvaried for bolt diameter and grade,and for bolts with short or noplain shank length, but in mostcases for bolts up to 1" or 20mmdiameter it is 10°. The bolt isloaded until it fractures, and thebreaking load must be above thespecified minimum. The load iscalculated from the tensile strengthof the material and the TensileStress Area of the thread.

The test requires that, in additionto meeting the specified minimumbreaking load, fracture must occurin the thread or plain shank withno fracture of the head shankjunction. The bolt head must,therefore, be capable of

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Fasteners your guarantee of quality industrial fasteners

Testing of Bolts & Nuts F A S T E N E R S

conforming with the requiredwedge taper angle withoutfracturing at its junction with theshank. This latter requirementprovides a very practical test forductility.

Where the capacity of availabletesting equipment does not permittesting of bolts in full size, ahardness test is carried out. This isperformed on a cross sectionthrough the bolt thread at adistance of 1 x diameter from theend.

(3) Proof Load Test for Nuts.The preferred method of testingnuts follows that of bolts inadoption of a test in full size tomeasure the load which the nutwill carry without its threadstripping. This is also referred to asa Proof Load Test and it wastraditional for the nut “Proof LoadStress” to be the same as thespecified minimum tensile strengthof the mating bolt. This “rule ofthumb” still applies for products tothe older standards such as BSWcommercial and unified high

tensile precision nuts. Metric nutsto AS 1112 - 1980 were designedwith greater knowledge of bolt/nutassembly behaviour to satisfy thefunctional requirement that theycould be used to tighten (bytorque), a mating bolt of the samestrength class up to its actual (notspecification minimum) yield stresswithout the assembly failing bythread stripping. To satisfy thisdesign requirement both thethickness/diameter ratio and proofload stress were increased andnow vary with diameter.

The nut is assembled on ahardened, threaded mandrel(Figure 8) and the proof loadapplied in an axial direction. Thenut must withstand this loadwithout failure by stripping orrupture, and be removable fromthe mandrel after the load isreleased.

Again, where nut proof loadsexceed the capacity of available, itis usual to carry out hardness testson the top or bottom face of thenut.

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7

Strength-Grade Designationsfor American and British

Standard Fasteners

F A S T E N E R S

Fasteners your guarantee of quality industrial fasteners

Table 4 American SAE Standard (AS 2465 is identical for Grades 2, 5, 8 only).

TensileSAE Head Diameter Strength “Proof Load” Rockwell

Grade Marking lbf/in2 Stress lbf/in2 Hardness(min.)

1 1/4" to 11/2" 60,000 33,000 B70-Bl00

2 1/4" to 3/4" 74,000 55,000 B80-Bl00over 3/4" to 11/2" 60,000 33,000 B70-Bl00

4 None 1/4" to 11/2" 115,000 65,000 C22-C32(studs only)

5 1/4" to 1" 120,000 85,000 C25-C34(Note 1) Over 1" to 11/2" 105,000 74,000 C19-C30

5.1 No.6 to 5/8" 120,000 85,000 C25-C40(Note 2)

5.2 1/4" to 1" 120,000 85,000 C26-C36(Note 3)

7 1/4" to 11/2" 133,000 105,000 C28-C34(Note 4)

8 1/4" to 11/2" 150,000 120,000 C33-C39(Note 5)

8.1 None 1/4" to 11/2" 150,000 120,000 C32-C38(studs only)

8.2 1/4" to 1" 150,000 120,000 C33-C39

NOTES: 1. Medium carbon steel, quenched and tempered.2. Sems (captive washer) assemblies. These are of low or medium carbon

steel, quenched and tempered.3. Low carbon boron steel, quenched and tempered.4. Medium carbon alloy steel, quenched and tempered. Thread rolled after

heat treatment.5. Medim carbon alloy steel, quenched and tempered.

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Fasteners your guarantee of quality industrial fasteners

Breaking & Yield Loads F A S T E N E R S

When bolts are broken in tension,breaking will normally occur inthe threaded section, and it mightbe expected that the breaking loadcould be calculated on the basis ofthe material strength and the areaat the root of the thread.

Tests have proved, however, thatthe actual tensile breaking load ofa bolt is higher than the figurecalculated in this manner, and themost accurate estimate is based onthe mean of the pitch and minor

diameters of the thread. Thiscalculation gives a figure which isknown as the “Stress Area”, andthis is now generally accepted asthe basis for computing thestrength in tension of an externallythreaded part. Stress Area isadopted for strength calculationsin I.S.O. recommendations and inspecifications issued by theStandards Association of Australia,British Standards Institution,American Society of AutomotiveEngineers (SAE).

Area of Stress Yield Load Breaking LoadSize Root of Area of of bolt (min.) of bolt (min.)

Thread Thread*

Sq. in. Sq.in. Tonf lbf Kn Tonf lbf Kn3/16 BSW 0.0141 0.0171 0.27 600 2.73 0.48 1070 4.771/4 BSW 0.0272 0.0321 0.51 1140 5.12 0.90 2010 8.965/16 BSW 0.0457 0.0527 0.84 1880 8.40 1.47 3290 14.73/8 BSW 0.0683 0.0779 1.25 2800 12.4 2.18 4880 21.77/16 BSW 0.0941 0.1069 1.71 3830 17.0 2.99 6700 29.81/2 BSW 0.1214 0.1385 2.22 4970 22.1 3.88 8690 38.65/8 BSW 0.2032 0.227 3.63 8130 36.2 6.35 14220 63.33/4 BSW 0.3039 0.336 5.38 12050 53.6 9.41 21080 93.77/8 BSW 0.4218 0.464 6.96 15590 69.3 13.00 29120 129

1 BSW 0.5542 0.608 9.12 20420 90.9 17.05 38190 170

11/8 BSW 0.6969 0.766 11.50 25760 114 21.42 47980 214

11/4 BSW 0.8942 0.980 14.70 32920 146 27.40 61480 273

11/2 BSW 1.300 1.410 21.15 47370 211 39.45 88370 393

13/4 BSW 1.753 1.907 28.60 64060 285 53.39 119590 532

2 BSW 2.311 2.508 37.60 84220 375 70.21 157270 700

Blacks BSW Bolts AS 2451

Table 5Based on: Tensile Strength = 28 tonf/in2 min.

Yield Stress = 16 tonf/in2 min. (to 3/4” diameter)15 tonf/in2 min. (over 3/4” diameter)

* See introductory paragraph to this section for definition of “Stress Area”.

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Breaking & Yield LoadsF A S T E N E R S

Fasteners your guarantee of quality industrial fasteners

* See introductory paragraph to this section for definition of “Stress Area”.

Area of Stress Yield Load Breaking LoadSize Root of Area of of Bolt (min.) of Bolt (min.)

Thread Thread*

Sq. in. Sq.in. Tonf lbf Kn Tonf lbf Kn3/16 BSW 0.0141 0.0171 0 22 500 2.22 0.44as 1000 4.431/4 BSW 0.0272 0.0321 0.41 940 4.16 0.84 1880 8.325/16 BSW 0.0457 0.0527 0.69 1540 6.83 1.37 3070 13.73/8 BSW 0.0683 0.0779 1.01 2270 10.1 2.03 4540 20.27/16 BSW 0.0941 0.1069 1.39 3110 13.8 2.78 6230 27.71/2 BSW 0.1214 0.1385 1.80 4030 17.9 3.60 8070 35.95/8 BSW 0.2032 0.227 2.95 6610 29.4 5.90 13220 58.83/4 BSW 0.3039 0.336 4.37 9780 43.5 8.74 19570 87.0

Blacks Cup Head BSW Bolts AS B108Table 6Based on: Tensile Strength = 26 tonf/in2 min.

Yield Stress = 13 tonf/in2 min.

Size Area of Stress Proof Load Breaking LoadRoot of Area of of Bolt of Bolt (Min.)Thread Thread*

Sq. in. Sq. in. lbf kN lbf kN

1/4 UNF 0.0326 0.0364 3100 13.8 4350 19.35/16 UNF 0.0524 0.0580 4900 21.8 6950 30.93/8 UNF 0.0809 0.0878 7450 33.1 10500 46.77/16 UNF 0.1090 0.1187 10100 44.9 14200 63.21/2 UNF 0.1486 0.1599 13600 60.5 19200 85.45/8 UNF 0.240 0.256 21800 97.0 30700 1373/4 UNF 0.351 0.373 31700 141 44800 1997/8 UNF 0.480 0.509 43300 193 61100 272

1 UNF 0.625 0.663 56400 251 79600 354

11/8 UNF 0.812 0.856 63300 282 89900 400

11/4 UNF 1.024 1.073 79400 353 112700 501

11/2 UNF 1.521 1.581 117000 520 166000 738

Blacks Unified High Tensile HexagonHead Bolts and Set Screws(AS 2465/SAE Grade 5)Table 7Based on: Tensile Strength = 120000 lbf/in2 min. (827 MPa) Sizes 1/4” - 1” incl.

= 105000 lbf/in2 min. (724 MPa) Sizes 11/8” - 11/2” incl.Yield Stress = 92000 lbf/in2 min. (634 MPa) Sizes 1/4” - 1” incl.

81000 lbf/in2 min. (558 MPa) Sizes 11/8” - 11/2” incl.Proof Load Stress = 85000 lbf/in2 (586 MPa) Sizes 1/4” - 1” incl.

74000 lbf/in2 (510 MPa) Sizes 11/8” - 11/2” incl.

* See introductory paragraph to this section for definition of “Stress Area”.Blacks stock range shown in bold face. Other sizes to special order.

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Fasteners your guarantee of quality industrial fasteners

Breaking & Yield Loads F A S T E N E R S

Size Area of Stress Proof Load Breaking LoadRoot of Area of of Bolt of Bolt (Min.)Thread Thread*

Sq, in. Sq. in. lbf kN lbf kN

1/4 UNC 0.0269 0.0318 2700 12.0 3800 16.9

5/16 UNC 0.0454 0.0524 4450 19.8 6300 28.0

3/8 UNC 0.0678 0.0775 6600 29.4 9300 41.4

7/16 UNC 0.0933 0.1063 9050 40.3 12800 56.9

1/2 UNC 0.1257 0.1419 12100 53.8 17000 75.65/8 UNC 0.202 0.226 19200 85.4 27100 1213/4 UNC 0.302 0.334 28400 126 40100 1787/8 UNC 0.419 0.462 39300 175 55400 246

1 UNC 0.551 0.606 51500 229 72700 323

11/8 UNC 0.693 0.763 56500 251 80100 356

11/4 UNC 0.890 0.969 71700 319 101700 452

11/2 UNC 1.294 1.405 104000 463 147500 656

Blacks HexagonHead Bolts and Set Screws(AS 2465/SAE Grade 5)

Table 8Based on: Tensile Strength = 120000 lbf/in2 min. (827 MPa) Sizes 1/4” - 1” incl.

= 105000 lbf/in2 min. (724 MPa) Sizes 11/8” - 11/2” incl.Yield Stress = 92000 lbf/in2 min. (634 MPa) Sizes 1/4” - 1” incl.

81000 lbf/in2 min. (558 MPa) Sizes 11/8” - 11/2” incl.Proof Load Stress = 85000 lbf/in2 (586 MPa) Sizes 1/4” - 1” incl.

74000 lbf/in2 (510 MPa) Sizes 11/8” - 11/2” incl.

* See introductory paragraph to this section for definition of “Stress Area”.Blacks stock range shown in bold face. Other sizes to special order.

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11

Breaking & Yield LoadsF A S T E N E R S

Fasteners your guarantee of quality industrial fasteners

Size Area of Stress Proof Load Breaking LoadRoot of Area of of Bolt of Bolt (Min.)Thread Thread*

Sq, in. Sq. in. lbf kN lbf kN

1/4 UNF 0.0326 0.0364 4350 19.3 5450 24.25/16 UNF 0.0524 0.0580 6950 30.9 8700 38.73/8 UNF 0.0809 0.0878 10500 46.7 13200 58.77/16 UNF 0.1090 0.1187 14200 63.2 17800 79.21/2 UNF 0.1486 0.1599 19200 85.4 24000 1075/8 UNF O.240 0.256 30700 137 38400 1713/4 UNF 0.351 0.373 44800 199 56000 2497/8 UNF 0.480 0.509 61100 272 76400 340

1 UNF 0.625 0.663 79600 354 99400 442

11/8 UNF 0.812 0.856 102700 457 128400 571

11/4 UNF 1.024 1.073 128800 573 161000 716

11/2 UNF 1.521 1.581 189700 844 237200 10551/4 UNC 0.0269 0.0318 3800 16.9 4750 19.35/16 UNC 0.0454 0.0524 6300 28.0 7850 30.93/8 UNC 0.0678 0.0775 9300 41.4 11600 46.77/16 UNC 0.0933 0.1063 12800 56.9 15900 63.21/2 UNC 0.1257 0.1419 17000 75.6 21300 85.45/8 UNC 0.202 0.226 27100 121 33900 1373/4 UNC 0.302 0.334 40100 178 50100 1997/8 UNC 0.419 0.462 55400 246 69300 272

1 UNC 0.551 0.606 72700 323 90900 354

11/8 UNC 0.693 0.763 91600 407 114400 457

11/4 UNC 0.890 0.969 116300 517 145400 573

11/2 UNC 1.294 1.405 168600 750 210800 844

Blacks HexagonHead Bolts and Set Screws(AS 2465/SAE Grade 8)

Table 9Based on: Tensile Strength = 150000 lbf/in2 min. (1034 MPa) Sizes 1/4” - 11/2” incl.

Yield Stress = 130000 lbf/in2 min. (896 MPa)Proof Load Stress = 120000 lbf/in2 (827 MPa)

* See introductory paragraph to this section for definition of “Stress Area”.

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Fasteners your guarantee of quality industrial fasteners

Breaking & Yield Loads F A S T E N E R S

Size Area of Tensile Stress Proof Load Breaking LoadRoot of Area of of Bolt of Bolt (Min.)Thread Thread

mm2 mm2 kN lbf kN lbf

M5 12.7 14.2 3.20 719 5.68 1277

M6 17.9 20.1 4.52 1016 8.04 1807

M8 32.8 36.6 8.24 1852 14.6 3282

M10 52.3 58.0 13.0 2923 23.2 5216

M12 76.2 84.3 19.0 4271 33.7 7576

M16 144 157 35.3 7936 62.8 14118

M20 225 245 55.1 12387 98.0 22031

M24 324 353 79.4 17850 141 31698

M30 519 561 126 28326 224 50357

M36 759 817 184 41365 327 73513

M42 1050 1120 252 56652 448 100714

M48 1380 1470 331 74412 588 132188

M56 1910 2030 458 102963 812 182545

M64 2520 2680 605 136009 1072 240995

Blacks Metric Hexagon CommericalBolts and Screws(AS 1111 Property Class 4.6)

Table 10Based on: Tensile Strength = 400 MPa min (58015 lbf/in2)

Yield Stress = 240 MPa min (34810 lbf/in2)Proof Load Stress = 225 MPa (32635 lbf/in2)

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Breaking & Yield LoadsF A S T E N E R S

Fasteners your guarantee of quality industrial fasteners

Size Area of Tensile Stress Proof Load Breaking LoadRoot of Area of of Bolt of Bolt (Min.)Thread Thread*

mm2 mm2 kN lbf kN lbf

M5 12.7 14.2 8.23 1850 11.35 2552

M6 17.9 20.1 11.6 2608 16.1 3619

M8 32.8 36.6 21.2 4766 29.2 6564

M10 52.3 58.0 33.7 7576 46.4 10431

M12 76.2 84.3 48.9 10993 67.4 15152

M16 144 157 91.0 20458 125 28101

M20 225 245 147 33047 203 45636

M24 324 353 212 47660 293 65869

M30 519 561 337 75760 466 104761

M36 759 817 490 110156 678 152421

Blacks Metric Hexagon PrecisionBolts and Screws(AS 1110 Property Class 8.8)

Table 11Based on: Tensile Strength = 800 MPa min (116030 lbf/in2) Sizes M5 - M16 incl.

= 830 MPa min (120380 lbf/in2) Sizes M20 - M36 incl.Yield Stress = 640 MPa min (92825 lbf/in2) Sizes M5 - M16 incl.

= 660 MPa min (95725 lbf/in2) Sizes M20 - M36 incl.Proof Load Stress = 580 MPa (84120 lbf/in2) Sizes M5 - M16 incl.

= 600 MPa (87025 lbf/in2) Sizes M20 - M36 incl.

* See introductory paragraph to this section for definition of “Stress Area”.

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Fasteners your guarantee of quality industrial fasteners

Bolt Shear Capacity F A S T E N E R S

Table 12

Specification AS 1111 AS 1110 Prop. Cl. 8.8 AS 1110 Prop. Cl 10.9AS 2451 AS 2465 Grade 5 AS 2465 Grade 8

Minimum Breaking Load in Single Shear – kN 1 2

Size Shank3 Thread Shank3 Thread Shank3 Thread

Coarse Fine Coarse Fine

M6 7 4 14 9 18 121/4" 9 5 16 9 11 20 11 14

M8 13 8 25 16 33 215/16" 13 8 26 15 17 32 19 223/8" 19 12 37 23 27 46 28 34

M10 20 13 39 26 51 347/16" 26 16 50 31 36 63 39 45

M12 28 19 57 38 74 501/2" 34 21 65 42 50 82 52 62

M16 50 36 101 72 131 945/8" 53 35 102 67 80 128 84 1003/4" 77 53 147 101 117 184 126 146

M20 79 56 163 117 204 1467/8" 105 73 201 140 160 251 175 200

M24 113 81 235 168 294 211

1" 137 97 262 184 208 327 230 260

11/8" 173 121 332 202 237 414 289 338

M30 177 130 368 270 459 337

M36 254 190 529 395 662 493

11/2" 308 226 589 377 444 736 539 634

NOTES:1. Tabulated values are for failure. Refer to applicable Code for permissible

Design Stress. Table 13 gives guidance for AS 1250 and AS 4100 values2. The values shown are for a single shear plane and may be compounded for

multiple shear planes. Multiple bolt joints are subject to an “unbuttoningeffect”.AS 1250 states that this should be considered when more than 5 bolts arealigned in the direction of the force.AS 1511 reduces design shear capacity, 14% for joints 500-1200mm length,43% for joints over 1200mm.AS 4100 progressively reduces design shear capacity by 25% for joints 300-1300mm length and longer.

3. Based on nominal diameter of shank.

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NOTES1. Basis is ultimate shear stress equals 62% of ultimate tensile strength. Reference

AS 4100-1990. This ratio was established on tension loaded lap joints. Geometriceffects on compression loading similar joint configuration can give apparent boltshear capacity 9% higher.

2. For overload protection application, check that both maximum and minimum aresuitable. Maximum equals minimum (Table 12) value times ratio.

3. Maximum shear stress at failure is based on imputed maximum tensile strength,estimated from specified maximum hardness. Reference SAE J417.

4. Maximum Permissible Shear Stress in design is the lesser of .33Fyf and 0.25Fuf.5. AS 4100 does not express stress values but extends the data to a “Design Resistance

Capacity” taking account of the length of the joint (see Table 12 Note 2), the availablebolt shear area (threads or shanks) and a “Capacity Factor” which is 0.8 for theStrength Limit State Criterion. Thus the “Design Capacity Shear Stress” shown hereto facilitate comparison with the previous rule is 80% of the minimum shear stress atfailure shown in column 2, and represents the stress value which the factored actions(loads) acting on the bolts may not exceed - not the actual shear stress which maynot be applied to the bolts. With Load Factors of 1.25 on dead loads and 1.5 on liveloads it can be seen that bolt loading is still conservative compared to their ultimatecapacity although less so than under AS 1250 rules. Other load factors apply for otheractions eg. earthquake, wind etc.

6. For mild steel bolts the relevant criterion (see Note 4 above) is generally .33Fyf.AS 2451 does not specify Fyt so the values shown are from Blacks Fasteners Ltd data.

7. On the basis of Note 1, the value here would be 297.6 MPa but 320 MPa is shown asit is a specified requirement of AS 1559.

8. Some Design Authorities have for over 5 years, used a value 290 MPa (=91% of thespecified minimum value) which would be experienced by the fastener under the80 year mean return wind, in lattice tower design. They previously used the 30 yearmean return wind and had some towers blow down.

9. Factoring the specification minimum shear stress would give a value of 256 MPa.10. kN x 224.809 = lbf. MPa x 145.038 = lbf/in2.

Table 13

Shear Stress AS 1250–1981 AS 4100–1990at failure1 Maximum Maximum

(Mpa) Permissible “DesignDesign Shear Capacity

Min Max Ratio2 Stress Shear Stress”5

Bolt Type (MPa)4 (MPa)

AS 1111 Property Class 4.6 248.0 431.5 1.74 79.2 198.4

AS 2451 BSW

Low Tensile 1/4" – 3/4" 267.8 452.6 1.69 (81.5)6 214.37/8" – 1" 267.8 452.6 1.69 (76.6)6 214.3

AS 1559 Tower Bolt 320.07 – – 112.28 238.19

AS Property Class 5.8 322.4 431.5 1.34 130.0 257.9

AS 1110 Property Class 8.8

M1.6 – M16 496.0 636.1 1.28 200.0 396.8

M18 – M36 514.6 654.1 1.27 207.5 411.7

AS 2465 Unified Grade 51/4" – 1" 512.7 654.1 1.28 206.8 410.2

11/8" – 11/2" 448.9 589.6 1.31 181.0 359.1

AS 2465 Unified Grade 8 641.0 752.1 1.17 258.5 512.9

AS 1110 Property Class 10.9 644.8 752.1 1.17 260.0 515.8

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F A S T E N E R SDesign of Bolted Joints forGeneral Engineering

Selection of TensileStrength of Bolts

Bolted joints in which strength isthe main design consideration, can,in most cases, be moreeconomically designed when ahigh tensile bolt is used ratherthan a mild steel bolt. Fewer boltscan be used to carry the same totalload, giving rise to savings notonly from the cost of a smallernumber of bolts, but alsomachining where less holes aredrilled and tapped, and assemblywhere less time is taken.

Selection of Coarseand Fine Threads

In practically all cases the coarsethread is a better choice. Thecoarse threads provide adequatestrength and great advantages inassembly over fine threads. Theformer are less liable to becomecross threaded, start more easily,particularly in awkward positions,and require less time to tighten.

In cases where fine adjustment isneeded, the fine thread should beused. Providing bolts are tightenedto the torque specified in Tables18-23 there should be no tendencyto loosen under conditions ofvibration with either coarse or finethreads.

Types of Loading onJoints

Examine the forces being appliedto the joint to decide which of thefollowing types fits the conditions.

a) Joints carrying direct tensileloads (See Fig. 9).

b) Joints carrying loads in shear(See Fig. 10-11). Types 1 and 2.

c) Flexible gasket joints forsealing liquids or gases underpressure (See Fig. 12).

Joints Carrying DirectTensile Loads

(1) Safety Factor. Apply a safetyfactor according to the nature ofthe loading. Except in the case ofthe flexible gasket joint, the safetyfactor on a bolt differs from mostother applications in that it doesnot affect the stress of the bolt, butrefers to the factor by which thesum of the preload on all the boltscomprising the joint exceeds thedesign load applied. Regardless ofthe nature of the load, the boltsshould still be preloaded to 65% oftheir yield stress using therecommended torque values as setout in Table 18-23.

Safety Factor =

Sum of preload on all the boltscomprising the joint

Design applied load

For design purposes, the preloadon each bolt should be takenaccording to the bolt size and boltmaterial as shown in Tables 18 to

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Design of Bolted Joints forGeneral Engineering

23 and the safety factor selectedfrom the following table:-

Table 14

Nature of Loading Safety Factors*

Steady Stress 1.5 – 2

Repeated Stressgradually applied 2 – 3.5shock 4.5 – 6

* Applies to joints with direct tensileloads only and assumes all bolts aretightened to 65% of the yield stress.

(2) Total Required Preload†.Determine this from safety factor(S) and applied load (L).

Total required preload F = S x L

(3) Selection of BoltMaterial, Bolt Size, Numberof Bolts. By selecting a suitablebolt size and bolt material, therequired number of bolts can bedetermined from –

N = Ff

Where N is the number of bolts, Fis the total required preload and fis the recommended preload (seeTables 18-23) on the bolt for theparticular size and materialselected.

(4) Specify TighteningTorque. Ensure that the bolts arefully tightened to the torquerecommended in Tables 18-23 forthe particular bolt size andmaterial.

(5) Positioning of the Bolts.The bolts should be placed as nearas possible to the line of directtensile load. By doing this,secondary bending stresses in thebolts and bolted members arereduced to a minimum.

Joints Carrying Loadsin Shear

The design procedure formechanical joints carrying thistype of loading can be based onwell established practice laid downfor structural joints carrying staticloads, provided the design loadsare increased by adequate factorsto allow for cyclic loads, shock, etc.These factors will varyconsiderably according to theapplication, and must be based onthe designer’s experience. Boltedjoints carrying loads in shear fallinto two types:-

1. Joints in which the load istransferred through the boltedmembers by bearing of themember on the shank of thebolt and shear in the bolt.

2. Friction type joints, where theload is transferred by thefriction developed between themembers by the clampingaction of the bolts.

† Note: At time of publication there are no “Allowable Stress” code provisions forgeneral mechanical engineering design of bolted joints. This information isprovided for guidance only.

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F A S T E N E R SDesign of Bolted Joints forGeneral Engineering

Load Transfer byBearing and Shear

Such joints may be designed usingallowable values for shear in thebolts and bearing on the jointmembers such as those given inAS 1250 or under the limit statesprovisions of AS 4100.

Guidance on bolt shear capacity isgiven on page 14. The loweststrength, whether it be in shear orbearing, is used to compute therequired number of bolts to carrythe design load.

The allowable values for shear andbearing depend not only on boltsize, but also on the tensilestrength of the bolt, and whetherthe bolt is in a close fittingmachined hole (not greater than0.25mm clearance) or is fitted in aclearance hole (up to 2-3mmclearance).

Careful consideration should begiven to the properties of thematerial in the bolted members toensure they are capable ofwithstanding bearing loads. Tensilestrength and yield stress of Blacksbolts can be obtained from Tables5-11. Care must be taken that thepitch of the bolt spacing issufficient to ensure that the boltedmembers are not weakened by the

bolt holes to the extent that theycannot safely carry the load. Toachieve this it may be necessary touse more than one row of bolts.Staggering of bolt holes canminimise reduction of membercapacity. If more than twomembers are bolted togetherslightly higher values are permittedin bearing on the central member,and the area considered forcalculating strength in shear isincreased by two or four times forbolts in double or quadruple shear.

Friction Type Joints

These joints are made up usinghigh strength bolts fitted inclearance holes and tightenedunder careful control to develop apreload equivalent or greater thanthe bolt yield load.

The mechanism of carrying load isby friction developed between themating faces, and it is wellestablished that this type of joint isconsiderably stronger than ariveted joint. Refer to AustralianStandard 4100.

General Rules toReduce Possibility ofBolt Failure Due toFatigue

The following general rules shouldbe observed to minimisepossibility of fatigue of bolts underhigh alternating or fluctuatingstresses.

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Design of Bolted Joints forGeneral Engineering

(1) Most Important. Tightenbolt effectively to ensure aninduced tension or preload inexcess of the maximum externalload.

(2) Bolt extension in tighteningshould be high. This can beachieved by:-

a) At least 1 x bolt diameter of“free” thread length under thenut.

b) Use of small high strengthbolts in preference to largerlow strength bolts.

c) In extreme cases a “waistedshank” bolt can be considered.

(3) Rolled threads are preferable tomachined threads.

(4) Under conditions of extremevibration the use of locknuts suchas the Conelock or Nyloc nutshould be considered to avoidpossibility of a loosened nutvibrating right off the bolt beforedetection.

(5) Bolt head and nut should be onparallel surfaces to avoid bending.

(6) Non axial bolt loadingproducing a “prising” actionshould be avoided where possible.

Flexible Gasket Jointsfor Sealing Liquids orGases Under Pressure

This type of joint differs from thetwo preceding types in that thestress in the bolt varies with theworking load.

This is because the flexible gasketmaterial has a much lower elasticmodulus than the bolt, andcontinues to exert virtually thesame force on the bolts whenadditional load is applied to thejoint. The resulting effect is that theworking load is added to the boltpreload in this case, so the designprocedure must be modifiedaccordingly.

(1) Design Pressure Load.Determine the design load Q onthe joint by multiplying theeffective area A on which thepressure is acting by the liquid orgas pressure P by S where S is thesafety factor selected from Table14.

Q = APS

(2) Total Preload Required.To the design pressure load, Q add10%, and this is the sum of thepreload F that should be applied tothe bolts comprising the joint.

F = Q + 10Q100

i.e. F = 1.1Q

(3) Total Design Load onBolts. In the case of a flexiblegasket type of joint the designpressure load Q on the joint isadded to the preload F on thebolts, giving the total design loadW on the bolts.

W = Q + F

(4) Select Bolt Material. Fromthe following table of yield stressesselect the bolt material.

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F A S T E N E R SDesign of Bolted Joints forGeneral Engineering

Table 15

Proof Load StressBolt Type lbf/in2 MPa

Blacks AS 2451 Bolts –1/4” – 3/4” 35,900 248Over 3/4” 33,600 232

Blacks MetricCommerical Bolts 32,630 225

Blacks Metric PrecisionPC 8.8 Bolts 95,725 660

Blacks SAE Grade 5 High Tensile Bolts –

1/4” – 1” 85,000 586

Blacks SAE Grade 8High Tensile Bolts 120,000 827

(5) Select Bolt Size andDetermine Number of Bolts.From the desired bolt size andcorresponding Stress Area “As”, (seeTables 5-11) determine the numberof bolts N from the yield stress Yand the total design load W on thebolts.

Number of bolts required N = WYAs

(6) Setting of TighteningTorque. In this case the bolts canonly be tightened to a preload wellbelow the yield stress so the torque

figure T for the bolt size andmaterial selected listed in Tables18-23 must be reduced bymultiplying by a factor of 0.806.

Tightening torque to be applied tobolts of a flexible gasket type ofjoint.

t = 0.8 T

Metal to MetalPressure Tight Joints

The stress in the bolts in a flexiblegasket type joint varies with load,and under rapidly fluctuatingloads they can be subject tofatigue. It is therefore desirable touse wherever possible, metal tometal pressure tight joints, as theseare not subject to fatigue.

The design procedure for a metalto metal pressure tight joint isexactly the same as for jointscarrying direct tensile loads oncethe pressure load is determined.

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How a Bolted JointCarries Load

A bolted joint can carry loads intension (Fig. 13), in shear (Fig. 14)or by a combination of these.

The static load capacity of the jointwill be determined largely by thesize, strength grade and number ofbolts installed. The capacity of abolted joint to maintain integrityindefinitely under dynamicloading is dependent on installingthe bolts with sufficient tension toprevent relative movement of thejoined members.

Tension

The external load is resisteddirectly by bolt tension. If thejoined members are rigid and thebolts are pretensioned, the matingfaces will not separate until theexternally applied load exceeds thetotal preload. This is because stressand strain are fundamentallyrelated (the relationship constant iscalled Young’s modulus in therange of elastic behaviour), so thatthe joint can’t separate until thebolt length increases and the boltlength can’t increase until thetension in it exceeds the preload(assuming service temperaturebelow the creep range). Thisconcept is valid when the jointmembers are stiffer (suffer lessstrain under a given force) thanthe bolt shank. It is true enough tobe important even when the jointmembers and bolt are of the samematerial (e.g. steel), i.e., have thesame modulus, because the area incompression between the bolthead and nut is much greater than

the area of the bolt shank intension and so compresses muchless than the bolt extends at anygiven bolt tension. Thus cyclicexternal load is experienced moreas a change in pressure at the jointface than a change of tension inthe bolt and in a well designedjoint, the stress range in the boltswill be below their fatigueendurance limit.

Shear

The pre-load in the bolt(s)clamping the members togetherproduces friction between themwhich resists the external load. Theexternal force which this friction iscapable of resisting withoutmovement is proportional to thepreload in the bolts and thecoefficient of friction on the matingsurfaces. When the frictional loadtransfer capacity is exceeded theultimate capacity of the joint willbe determined by shear on thefasteners and bearing on the joinedmembers.

Methods of Control ofBolt Tightening

Several methods are available forcontrolling the establishment of adesired level of preload in boltswith the cost rising with increasingaccuracy more or less as indicated

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Tightening of Bolted Joints F A S T E N E R S

in Table 16. Each method has itsapplications and the choice shouldbe made after an assessment of theparticular requirements.

(1) Torque

Although torque bears no fixedrelationship to fastener tension, theuse of torque wrenches is the mostcommon method of pre-loadcontrol because of simplicity andrelative economy. Many factors,including surface texture (cut orrolled threads), surface coatings-lubrications, thread interference,speed of tightening, etc., affect thetorque-tension relationship andup to +25% variation in pre-load,has been measured on similarfasteners receiving identical torque.Closer control of torque/tensioncalibration for a particular lot canreduce variation to +15%. Withmanual torque wrenches, thetorque may be reset from or readoff a built-in scale. Power tools aremore productive when largenumbers of bolts are to betightened and may be pneumatic,electric or hydraulic, but generallyrequire tightening of sample boltsin a bolt load measuring device toset a pressure regulator or stall-torque for the desired bolt tensionrather than measuring torquedirectly. This requirement will give

more accurate control of tension ifsetting is performed under jobconditions with the bolts to betightened.

Torquing of Bolts andNuts

The purpose of controlling thetorque applied to a fastenerassembly is to induce a desiredlevel of tensile force in the bolt(equals clamping force on thejoint). Unless limited by somecharacteristic of the joint (e.g., asoft gasket), the amount of tensionaimed for in general engineeringpractice is 65-75% of the minimumelastic capacity (proof load) of thebolt. By selecting bolts such thatthis level of tension is not exceededby service load on the joint,loosening of the nut should not bea problem in most applications.Nyloc or Conelock nuts arerecommended for joints wheresuch pre-tensioning is notapplicable and as an addedinsurance against loss of the nut,should the initial pre-tension belost. The 65-75% of Proof Loadlevel of pre-tension is sufficientlyconservative to give reasonablyreliable torque controlledtightening with indefinite

Table 16

Preload Measuring Method % Accuracy Relative Cost

Feel (Operators Judgement) ± 35 1

Torque Wrench ± 25 11/2

Turn-Of-The-Nut ± 15 3

Load Indicating Washers ± 10 31/2

Fastener Elongation ± 3 – 5 15

Strain Gauges ± 1 20

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reuseability of the assembly. Forcritical applications closer controlor calibration checking isrecommended. Because friction isthe major unknown variableaffecting the relationship betweentorque applied and tensioninduced, the presence of light oillubrication is the minimumstandard recommended forconsistency in controlledtightening of fasteners. Most plainfinish fasteners are supplied with asufficient oil residue from theirprocessing but plated finishes willgenerally require oiling oradjustment to the torquerecommended in Blacks FastenersLtd Technical Data. For bolts withspecial surface finishes orassembled with anti-seizecompounds or heavily greased, thetorque-induced preloadrelationship is likely to be alteredand the recommendations torequire modification.

Table 17 lists factors based onaverages for the torque-inducedpreload relationship by which thetabulated figures should bemultiplied to correct for the mostcommon surface conditionvariations. For other surfacetreatments or for specialised boltassemblies involving higherpreload requirement or speciallock nut, etc., it may be desirable toexperimentally determine thetorque-induced preloadrelationship. Attention is drawn tothe fact that because static frictionis greater than dynamic friction,the best accuracy and consistencyof torque control tightening isobtained when rotation of thefastener is steadily maintained untilthe torque increases to the set level.

Allowing for this effect becomesmore important as the set torque isapproached; another purchaseshould be taken early enough toavoid stall before rotationcontinues. Difficulty maintainingsteady movement up to the settorque is a drawback of somehydraulic tools used for largediameter fasteners. The steadyimpacting of pneumatic tools givesbetter results.

(2) Strain Control

a) Part Turn Tightening: Thismethod involves imparting acontrolled strain or extensionto the bolt by measuringrelative rotation from thepoint where the joint membersare solidly compacted. It ismost widely used intensioning bolts in structuralsteel work.

b) Direct Tension Indicators:These proprietary devices arealso based on controlledstrain, but make use of designfeatures in a bolt head, nut orwasher to make the strainvisible and measurable as apermanent witness of properbolt tensioning.

c) Measurement of BoltExtension: This is a timeconsuming but very accuratemethod. Bolt Length may bemeasured before and aftertightening, with a micrometer

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in some joint configurations orby an electronic “sonar” typedevice from one end. Greatestaccuracy is achieved when thestrain value is obtained fromthe load extension curve of thefastener being used, butcalculation based on Hooke’sLaw gives good correlationwhen allowance is made forthe respective lengths andcross-sectional areas of theplain and threaded portions ofthe bolt shank effectively inthe grip.

d) Pre-assembly Straining: Themost common development ofthis method is the snugtightening of a normal nut ona bolt which has been heatedto produce a calculated degreeof thermal expansion. Ahollow bolt with ahydraulically actuated internalloading ram is available whichmakes removal as easy asinstallation.

e) Strain Gauges: These areusually applied to the bolt

Table 17

Surface Condition Factor

Galvanised – Degreased 2.1– Lightly oiled 1.1

Zinc Plated – Degreased 0.7*– Lightly oiled 0.9

Cadmium Plated – Degreased 1.0– Lightly oiled 0.7

Phosphated and oiled 0.7

Standard finish plus heavy grease 0.7

* In previously published guidance for tightening by control of applied torque thisfactor shown as 1.9.Investigation of a 1991 complaint that assemblies torqued at this level werestripping found that the factor 0.7 is now appropriate. The writer conjectures thatthis variation is attributable to the change in plating practice from alkali-cyanideto acid chloride zinc plating electrolyte since this data was generated andperhaps more specifically to different lubricity of the brighteners used in theseproprietary solutions.The change emphasises that such published general information can only everbe regarded as a guide and verification of applicability for a specific applicationis advisable both initially and over time, particularly if any parameters are knownto have changed.It should be remembered also that such guidance is based on first tightening ofsingle assemblies in isolation and that interactions in multifastener joints mayresult in changes to initial tension such that a detailed tightening sequence mayneed to be developed and followed for satisfactory service of the joint.As well as scatter in the torque-tension relationship for different assemblies fromthe same lot, retightening of the same bolt may give a different torque tensionrelationship. Both the scatter and shift on retightening are minimised by goodlubrication of threads and bearing face.In recent tests of bright zinc plated parts the tension at a given torque was foundto progressively reduce by 50% over five tightenings of an unlubricated assemblywhile a well lubricated assembly showed no reduction over five retightenings andonly a 9% over twelve retightenings. The results of these tests are shown inGraphs 1-4.

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shank and calibrated in a loadmeasuring machine.

(3) Combination Methods

Electronic sensors andmicroprocessors have beendeveloped which simultaneouslymeasure torque and/or angularrotation and/or instantaneousrate of change in thesecharacteristics. Hand-held modelsare available with capacity forhe size range common inautomotive application but themethods are essentially confinedto high volume application suchas the simultaneous tighteningof automotive engine head “bolts”(really cap screws). Theiraccuracy allows designs for boltstensioned to their actual yieldpoint and the implementation ofthis method has resulted in re-design with higher strength ofstandard metric nuts so that they

are unlikely to strip on bolts sotightened.

(4) Direct Tensioning

In the most economicdevelopment of this method,tension applied by a calibratedhydraulic jack attached to anextension of the bolt or studthread is transferred to a normalnut after it is snugged up to thejoint. The relaxation of tension dueto bedding in and deflection of themating threads is consistent forgiven assembly types and can beallowed for to maintain accuracyof the desired residual tension. Thismay be the most practicablemethod for bolts over M36/11/2"diameter and is particularlysuitable for sealing of highpressure gasketed joints becausemanifolding of jacks enablessimultaneous, uniform tensioningof many bolts.

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Table 18 Recommended Assembly Torques

Bolt Tension RecommendedCorresponding to Assembly

Bolt Diameter 65% of Proof of Load TorqueType mm kN lbf Nm ft.lbs

AS 1111 5 2.08 468 2.1 1.5

Blacks Property 6 2.94 661 3.5 2.5

Class 4.6 8 5.34 1200 8.5 6.3

Commercial Low 10 8.45 1900 17 12

Tensile Bolts 12 12.4 2788 30 22

16 22.9 5148 7.3 54

20 35.8 8048 14.3 106

24 51.6 11600 248 183

30 81.9 18412 491 362

36 120 26977 864 637

42 164 36869 1378 1016

48 215 48334 2064 1522

56 298 66993 3338 2462

64 393 88350 5030 3710

The torques listed are for plain finish (uncoated) fasteners as supplied. Refer topage 24 and table 17 for effects of various finishes.

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Table 19 Recommended Assembly Torques

RecommendedInduced Bolt Preload Assembly Torque

Bolt Type Diameter or Tension to Give Inducedand Thread Corresponding to Preload Equal to

65% of Yield Load 65% of Yield Loadlbf lbf

AS 2451 1/4 BSW 750 3

Blacks BSW Low 5/16 BSW 1230 6

Tensile Bolts 3/8 BSW 1820 12

(Formerly AS B100) 7/16 BSW 2480 19

1/2 BSW 3250 28

5/8 BSW 5300 55

3/4 BSW 7830 98

7/8 BSW 10200 150

1 BSW 13300 230

11/8 BSW 16700 320

11/4 BSW 21500 450

11/2 BSW 30800 780

The torques listed are for plain finish (uncoated) fasteners as supplied. Refer topage 24 and Table 17 for effects of various finishes.

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F A S T E N E R STightening of Bolted Joints

Table 20 Recommended Assembly Torques

RecommendedInduced Bolt Preload Assembly Torque

Bolt Type Diameter or Tension to Give Inducedand Thread Corresponding to Preload Equal to

65% of Yield Load 65% of Yield Loadlbf lbf

AS 2465 1/4 UNF 2020 8

Blacks Grade 5 5/16 UNF 3190 17

Unified High 3/8 UNF 4840 30

Tensile Bolts 7/16 UNF 6570 48

(Same as SAE 1/2 UNF 8840 74

J429 Grade 5) 5/8 UNF 14170 150

3/4 UNF 20610 260

7/8 UNF 28150 410

1 UNF 36660 610

1/4 UNC 1760 7

5/16 UNC 2890 15

3/8 UNC 4290 27

7/16 UNC 5880 43

1/2 UNC 7870 66

5/8 UNC 12480 130

3/4 UNC 18400 230

7/8 UNC 25550 370

1 UNC 33480 560

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Tightening of Bolted Joints

Table 21 Recommended Assembly Torques

RecommendedInduced Bolt Preload Assembly Torque

Bolt Type Diameter or Tension to Give Inducedand Thread Corresponding to Preload Equal to

65% of Yield Load 65% of Yield Loadlbf lbf

AS 2465 1/4 UNF 2830 12

Blacks Grade 8 5/16 UNF 4520 23

Unified High 3/8 UNF 6830 43

Tensile Bolts 7/16 UNF 9230 67

(Same as SAE 1/2 UNF 12500 104

J429 Grade 8) 5/8 UNF 19960 207

3/4 UNF 29120 363

7/8 UNF 39720 577

1 UNF 51740 859

1/4 UNC 2470 10

5/16 UNC 4100 21

3/8 UNC 6050 38

7/16 UNC 8320 60

1/2 UNC 11050 92

5/8 UNC 17620 183

3/4 UNC 26070 325

7/8 UNC 36010 523

1 UNC 47200 785

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F A S T E N E R STightening of Bolted Joints

Table 22 Recommended Assembly Torques

Bolt Tension RecommendedCorresponding to Assembly

Bolt Type Diameter 65% of Proof Load Torquemm kN lbf Nm ft.lbs

AS 1110 5 5.4 1214 5 4

Blacks Property 6 7.6 1709 9 7

Class 8.8 8 13.8 3102 22 16

Precision High 10 21.9 4923 44 32

Tensile Bolts 12 31.8 7149 77 57

16 59.2 13309 190 140

20 95.6 21492 372 274

24 138 31024 640 472

30 219 49233 1314 969

36 319 71714 2297 1694

(42) 437 98242 3671 2707

(48) 573 128816 5500 4057

(56) 792 178049 8870 6542

(64) 1045 234925 13376 9866

AS 1110 covers sizes to M36 only. Data for sizes above this is given forinformation only. The Blacks Fasteners stocked range extends to M24 but sizes30, 36 Property Class 8.8 Bolts and Nuts are available from structural stocks.The torques listed are for plain finish (uncoated) fasteners as supplied. Refer topage 24 and Table 17 for effects of various finishes.

Table 23 Recommended Assembly Torques

Bolt Tension RecommendedCorresponding to Assembly

Bolt Type Diameter 65% of Proof Load Torquemm kN lbf Nm ft.lbs

AS 1110 5 7.67 1724 8 6

Blacks Property 6 10.86 2441 13 10

Class 10.9 8 19.76 4442 32 23

Precision High 10 31.27 7030 63 46

Tensile Bolts 12 45.50 10229 109 81

16 84.50 18996 270 200

20 131.95 29664 528 390

24 190.45 42815 914 675

30 302.90 68095 1817 1341

36 440.70 99073 3173 2342

The torques listed are for plain finish (uncoated) fasteners as supplied. Refer topage 24 and Table 17 for effects of various finishes.

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Tightening of Structural Joints

The design, fabrication,assembly and inspection ofsteel structures using metrichigh strength structuralbolts and nuts to AS 1252are covered in AS 4100 - SAASteel Structures Code whichshould be referred to formore detailed information.

The requirements for boltingCategories 8.8TF/8.8TB are inessence the same as thosepreviously given in AS 1511 –1984. The ASAA High StrengthStructural Bolting Code which waswithdrawn on 26/10/91.

The following are abstracts fromAS 4100.

(1) Assembly

Each bolt and nut shall beassembled with at least one washerand where only one washer isused it shall be placed under therotating component. Tightening ofthe bolts shall proceed from thestiffest part of the joint toward thefree edges.

Under no circumstances shall boltswhich have been fully tightened bereused in another joint orstructure. They may be retightenedonce in the same hole.

(2) Methods of Tightening

Tightening methods permitted canbe either “part turn method” or useof “direct tension indicators”(CoronetR Load Indicators).

a) Part Turn Tightening Method

On assembly all bolts and nuts inthe joint are first tightened to asnug tight condition. Snug tight isdefined as the tightness attained by

the full effort of a man using astandard podger spanner or by afew impacts of an impact wrench.Location marks are thenestablished to mark the relativeposition of the bolt and nut. Thebolts are then finally tightened bythe amount shown in Table 24.

b) Direct Tension Indicators1

Tightening of bolts and nuts shallbe in accordance with themanufacturer’s instructions andthe following procedure2. Onassembly all bolts and nuts in thejoint are first tightened to the snugtight condition. Then the bolt andnut are tightened to provide theminimum tension specified inTable 25.

b.1) This method of tightening canbe carried out with CoronetR LoadIndicators. Refer page 51.

b.2) AS 4100 requires that thesuitability of the device shall bedemonstrated by testing at leastthree specimens for each diameterand grade in a calibration devicecapable of indicating bolt tensionand proving that the deviceindicates a tension at least 105% ofthe specified minimum.

(3) Inspection

Bolts and nuts that show on visualinspection any evidence ofphysical defects shall be removedand replaced by new ones. Thefollowing methods shall be used tocheck that all bolts are fullytightened. For “part turn”tightening, by ensuring that thecorrect part turn from the snugposition can be measured orobserved. For “direct tensionindicator” tightening, by ensuring

Bolting Categories 8.8TF/8.8TB

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Tightening of Structural Joints F A S T E N E R S

Bolting Categories 8.8TF/8.8TB

that the manufacturer’s specifiedtightening procedure has beenfollowed and that the developmentof the minimum bolt tension isindicated by the tension indicatingdevice.

a) Direct Tension Indicators

Inspect according to themanufacturer’s recommendations.In the event that Blacks FastenersCoronetR Load Indicators havebeen used, these recommendationsare set out on page 51.

(4) Inspection of BoltTension using a TorqueWrench

a) In the event that the specifiedprocedure for part-turn tighteningie. method verification andapplication of match marking forlater inspection, was not followed

and direct tension indicators werenot installed some method forsubsequent checking of bolttension is sometimes required bythe inspection engineer.

Note that tightening by torquecontrol was found to be reliable inpractice, not least because fewerectors purchased the equipmentnecessary to perform theprocedure for calibration of thebolts/wrench combinations whichare to be used in the structure, andwas deleted from the SAA HighStrength Bolting Code. Logically, itis also not reliable for inspection ofthe correct tension in bolts either.

The procedure given in thefollowing is suitable for detectinggross under-tension, eg. boltswhich have been “snugged” only,but cannot be relied upon todistinguish bolts which although

Disposition of outer face of bolted parts (See notes 1, 2, 3, 4)

Bolt Length Both Faces One Face normal Both Faces(Underside of head normal to axis to bolt axis and slopedto end of bolt) other sloped

Up to and including 4 diameters 1/3 turn 1/2 turn 2/3 turn

Over 4 diameters but notexceeding 8 diameters 1/2 turn 2/3 turn 5/6 turn

Over 8 diameters but notexceeding 12 diameters(see note 5) 2/3 turn 5/6 turn 1 turn

Table 24 AS 4100 - 1990 Nut Rotation from the Snug-Tight condition.

NOTES1. Tolerance on rotation: for 1/2 turn or less, one twelfth of a turn (30°) over and

nil under tolerance; for 2/3 turn or more, one eighth of a turn (45°) over and nilunder tolerance.

2. The bolt tension achieved with the amount of nut rotation specified in Table24 will be at least equal to the minimum bolt tension specified in Table 25.

3. Nut rotation is the rotation relative to the bolt, regardless of the componentturned.

4. Nut rotations specified are only applicable to connections in which allmaterial within the grip of bolt is steel.

5. No research has been performed to establish the turn-of-nut procedure forbolt lengths exceeding 12 diameters. Therefore, the required rotation shouldbe determined by actual test in a suitable tension measuring device whichsimulates conditions of solidly fitted steel.

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tightened well beyond snug maynot have been fully tensioned.

NOTE:

The principal factors which limitthe reliability of the method are:-

a) the equivalence of thread andbearing face surface conditionand lubrication of thecalibration samples and jobbolts.

b) the occurrence of gallingduring tightening.

c) the time lapse betweentensioning and inspectionespecially as regards corrosionwhich may have occurred.

It is emphasised that correcttensioning can only be assuredby–

1. Using the correct bolts andnuts (Blacks AS 1252 HighStrength Structural)

2. Verifying proper snugging ofall bolts in the joint. (Thisshould be the time of firstinspection - joint should besolid)

3. Applying match marks -desirably permanent, orverifying about 1-2mm gap atCoronet load indicator. Theload indicator inherentlyprovides a permanent witnessof correct tensioning.

4. Witnessing that the toolingavailable can easily achieve therequired part-turn or crushthe load indicator to thespecified average gap.

Bolt TensionInformation forSetting InspectionWrenches

(4.1) Calibration

Inspection Wrench. Theinspection wrench may be either ahand-operated or adjustablepower-operated wrench. It shouldbe calibrated at least once per shiftor more frequently if the need toclosely simulate the conditions ofthe bolts in the structure sodemands.

The torque value determinedduring the calibration may not betransferred to another wrench.

The point being that there is no“inspection torque” for each sizeof bolt!

Each lot of bolts and each toolto be deployed must beindividually calibrated at thetime of tightening/inspection.

Adequately inspection with atorque wrench is virtuallyimpossible because it is practicallyimpossible to obtain samples forthe calibration procedure whichtruly represent the bolts to beinspected. This is illustrated by fig.15 which shows the torque-tension calibration of three M24galvanised bolt assembliessubmitted from a site by a partyrequired to apply torque-wrenchinspection.

Samples. At least three bolts,desirably of the same size(minimum length may have to beselected to suit the calibrationdevice) and conditions as those

Bolting Categories 8.8TF/8.8TB

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F A S T E N E R STightening of Structural Joints

under inspection should be placedindividually in a calibration devicecapable of indicating bolt tension.

IMPORTANT: Without thiscalibrating device torquewrench inspection to the code isnot possible!

A hardened washer should beplaced under the part turned.

Each calibration specimen shouldbe tensioned in the calibratingdevice by any convenient meansto the minimum tension shownfor that diameter in Table 25. Theinspection wrench then should beapplied to the tensioned bolt andthe torque necessary to turn thenut or bolt head 5 degrees(approximately 25mm at 300mmradius) in the tensioning directionshould be determined. The averagetorque measured in the tests of atleast three bolts should be taken asthe job inspection torque.

(4.2) Inspection

Bolts represented by the sampleprescribed in Paragraph B2 whichhave been tensioned in thestructure should be inspected by

applying, in the tensioningdirection, the inspection wrenchand its job inspection torque tosuch proportion of the bolts in thestructure as the supervisingengineer prescribes.

NOTE For guidance it is suggestedthat a suitable sample size wouldbe 10 percent of the bolts but notless than two bolts in eachconnection are to be inspected.

(4.3) Action

Where no nut or bolt is turned bythe job inspection torque, theconnection should be accepted asproperly tensioned. Where any nutor bolt head is turned by theapplication of the job inspectiontorque, this torque should then beapplied to all other bolts in theconnection and all bolts whosenut or head is turned by the jobinspection torque should betensioned and re-inspected.Alternatively, the fabricator orerector at is option, may retentionall of the bolts in the connectionand then resubmit the connectionfor inspection.

Bolting Categories 8.8TF/8.8TB

Table 25Bolt Tension Information forSetting Inspection Wrenches

Bolt Tension

Nominalbolt Minimumdiameter

kN Kips ton f

M16 95 21.3 9.5

M20 145 32.6 14.55

M24 210 48.6 21.7

M30 335 77.1 34.4

M36 490 112.9 50.3

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Tightening of Structural JointsBolting Categories 8.8TF/8.8TB

Figure 15This data, established on specimens returned from a site where inspection wasrequired by the responsible Engineer, illustrates the difficulty of applying torqueinspection to establish the correct tensioning of Bolting Categories 8.8TF/8.8TBconnections.The plotted points show tension against the more consistent dynamic friction (nutin motion) torque rather than the torque to overcome static friction of a stationarynut as in the procedure in the Australian Structural Steel Code. Either way thecalibration torque is determined on freshly tensioned assemblies which may ormay not be what is to be inspected.The first point for the M24 x 100 removed from the structure is plotted twice as thewrench ran out of travel before reaching the 270 Nm set point the first time.

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F A S T E N E R SStructural Design UsingBlacks Bolts

Acknowledgement: The followingsummary of design procedures to AS4100 - 1990 is by Arun Syam andArthur Firkins of AISC - TechnicalServices.

The two basic types of metric boltused in structural engineering inAustralia are:

• commercial bolts to AS1111 (Strength Grade 4.6)

• high strength structuralbolts to AS 1252 (StrengthGrade 8.8)

The design provisions forstructural bolts are contained inAustralian Standard 4100 - 1990:Steel Structures. This standard, inlimit states design format,superseded AS 1250 - 1981 whichwas in a working stress format. AS4100 - 1990 also incorporates thedesign and installation clauses ofhigh strength bolts from AS 1511 -1984: High Strength Bolting Code -which it also superseded.

Australian MaterialStandards

The relevant material standardsreferenced by AS 4100 – 1990 arethe current editions:

AS 1110 ISO metric hexagonprecision bolts andscrews.

AS 1111 ISO metric hexagoncommercial bolts andscrews.

AS 1112 ISO metric hexagonnuts, including thin nuts,slotted nuts and castlenuts.

AS 1252 High strength steel boltswith associated nuts andwashers for structuralengineering.

AS 1275 Metric screw threads forfasteners.

AS 1559 Fasteners – Bolts, nutsand washers for towerconstruction.

References

Further design guidance isavailable in the followingpublications by the AustralianInstitute of SteelConstruction (AISC):

[1] Design Capacity Tables forStructural Steel, 1st Edition, 1991.

[2] Bolting of Steel Structures, 3rdEdition, 1991.

[3] Design of Structural Connections,4th Edition, 1991.

[4] Economical Structural Steelwork,3rd Edition ,1991.

Bolting Categories

The strength of bolts is normallyspecified in terms of the tensilestrength of the threaded fastener.As a consequence, grades of boltsare identified in the followingmanner:

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Structural Design UsingBlacks Bolts

Grade X.Y(eg Grade 4.6 or Grade 8.8

where

X – is one hundredth of thenominal strength (MPa)

Y – is one tenth of the ratiobetween nominal yield stressand nominal tensile strengthexpressed as a percentage.

A standard bolting categoryidentification system has beenadopted in AS 4100-1990. Theseare:

• snug tightened (applies tocommercial and high strengthstructural bolts) designated4.6/S and 8.8/s respectively;

• fully tensioned friction type(high strength structural boltsonly) – designated 8.8/TF;

• fully tensioned, bearing type(high strength structural boltsonly) – designated 8.8/TB;

The system of category designationidentifies the bolt being used by using itsstrength grade designation (4.6 or 8.8)and identifies the installation procedureby a supplementary letter (S–snug; T–fulltensioning). For 8.8/T categories, the typeof joint is identified by an additionalletter (F–friction-type joint; B–bearingtype joint.

Category 4.6/S refers to

commercial bolts of StrengthGrade 4.6 conforming to AS 1111,tightened using a standard wrenchto a 'snug-tight' condition.

AS 4100-1990 describes 'snug-tight' as "the tightness attained bya few impacts of an impact wrenchor by the full effort of a personusing a standard podger spanner".The aim of this installation is toachieve a level of tightness so thatall plies in a joint are in fullcontact. It is a final mode of bolttightening for 4.6/S and 8.8/Sbolting categories, and the first stepin full tensioning to 8.8/TF and8.8/TB bolting categories – seebelow.

Category 8.8/S refers to any boltof Strength Grade 8.8 tightened toa 'snug-tight' condition asdescribed above. These bolts areused as a higher grade commercialbolt to increase the capacity ofcertain connection types.

Categories 8.8/TF and 8.8/TB (or8.8/T when referring to both bolttypes) refer specifically to highstrength structural bolts ofStrength Grade 8.8 conforming asAS 1252 fully tensioned in a controlledmanner to the requirements of AS 4100-1990. The benefit of this boltingcategory is the increase inperformance of the bolted joint inthe serviceability limit state (ielimited joint slip), though for apenalty of installed cost – see Refs[2] and [4] above-mentioned. It isrecommended that 8.8/TF categorybe used only in rigid joints wherea no-slip joint is essential.

See Table 26 for a summary of theabove types and bolting categories.

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F A S T E N E R SStructural Design UsingBlacks Bolts

Modes of ForceTransfer

In the design of individual bolts inbolted structural connections,there are three fundamental modesof force transfer to be considered.These are:

a) Shear/bearing modewhere the forces areperpendicular to the bolt axisand are transferred by shearand bearing on the bolt andbearing on the connected plies(see Fig 16). Relevant boltingcategories are 4.6/S, 8.8/S and8.8/TB;

b) Friction mode, which issimilar to the shear/bearingmode in that forces to betransferred are perpendicularto the bolt axis. However, thetransfer of forces does not relyon shear and bearing but isdependant upon the frictionalresistance of the matingsurfaces (see Fig 17). Therelevant bolting category is8.8/TF;

c) Axial tension mode, whenthe forces to be transferred areparallel to the bolt axis (see Fig18). All bolting categories mayapply to this.

These modes of force transfer mayoccur independently or with oneanother.

Minimum DesignActions on BoltedConnections asAS 4100-1990

Minimum design actions onconnections must be consideredand these are set out in Clause9.1.4 of AS 4100-1990. Also, boltswhich are required to carry adesign tensile force must beproportioned to resist anyadditional tensile force due toprying action.

Design Procedure toAS 4100-1990

AS 4100-1990 uses the limit statesdesign method in the design,fabrication, erection andmodification of steel work instructures. For a description of'limit states' reference should bemade to Ref [1] above. In limitstates design the followingfundamental inequality must besatisfied.

S* ≤ ø Ru

where

S* = design action effect (ie designshear load and/or designtension load) on the bolt

Ru = nominal capacity of the bolt

ø = capacity factor (from Table28, 29 of AS 4100)

This inequality states the designaction effect (S*) must be lessthan or equal to the design

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Structural Design UsingBlacks Bolts

capacity of the bolt (øRu) forthe design action considered. Thenominal capacity of the bolt isgiven in AS 4100-1990. It shouldbe noted that the design actioneffect (S*) is calculated from anacceptable form of analysis usingthe factored limit state load as setout in AS 1170-1989: MinimumDesign Loads on Structures(known as the SAA Loading Code).

In bolting design there are threelimit states that have to beconsidered. They are:

i) strength limit state;

ii) serviceability limit state;

iii) fatigue limit state.

STRENGTH LIMITSTATE

In AS 4100-1990 the strength limitstate design provisions whichapply for static load applicationsare found in Clause 9.3.2. Thisapplies for all the commonly usedbolting categories of 4.6/S, 8.8/S,8.8/TB and 8.8/TF.

Bolt in Shear –Strength Limit State

The following inequality must besatisfied for a bolt subjected to thedesign shear force (V*f) for strengthlimit state:

V*f ≤ ø Vf

where

ø = 0.8 (Table 3.4 of AS 4100-1990)

Vf = nominal shear capacity of abolt

Shear strengths obtained fromresearch have shown that, forbolts in shear, the average shearstrength of the bolt was 62% ofthe tensile strength (fuf). The shearstrength of a bolt is directlyproportional to the shear areaavailable, this being the core area(Ac) when considering thethreaded part of the bolt or theshank area (Ao) when consideringthe unthreaded part. Therefore, inAS 4100-1990 the nominal shearcapacity of a bolt (Vf) is given by:

Vf = 0.62fufkr(nnAc + nxAo)

where

fuf = minimum tensile strength ofthe bolt (see Table 26)

kr = reduction factor to accountfor the length of a bolted lapconnection – Lj (see Table29). For all other, kr=1.0

nn = number of shear planes withthreads intercepting theshear plane

Ac = minor (core) diameter area ofthe bolt as defined inAS 1275

nx = number of shear planeswithout threads interceptingthe shear plane

Ao = nominal plain shank area ofthe bolt

See Table 27 (Grade 4.6) and Table28 (Grade 8.8) for listings of boltdesign shear capacity – strengthlimit state (øVfn and ø Vfx) – for thecommonly used structural bolts.

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F A S T E N E R SStructural Design UsingBlacks BoltsNote: In Tables 27 and 28 –

øVfn = ø0.62fufAc for threadsincluded in single shear plane,and øVfx = ø0.62fufAo for threadsexcluded from single shear plane.

Bolt in Tension –Strength Limit State

The following inequality must besatisfied for a bolt subjected to adesign tension force (N*tf) forstrength limit state:

N*tf ≤ ø Ntf

where

ø = 0.8 (Table 3.4 of AS 4100-1990)

Ntf= nominal tension capacity ofa bolt = Asfuf

and

As = tensile stress area of a bolt asspecified in AS 1275

fuf = minimum tensile strength ofthe bolt (see Table 26)

See Table 27 (Grade 4.6) and Table28 (Grade 8.8) for the listings ofbolt design tensions capacity –strength limit state (øNtf) – for thecommonly used structural bolts.

Bolts that are fully tensioned have,for design purposes, no reductionin nominal tension capacity (seeRef [2] above.

Bolt Subject toCombined Shear andTension – StrengthLimit State

For bolts subject to simultaneousshear and tension forces, tests haveshown that the following ellipticalinteraction relationship applies:

V*f/øVf)2 = (N*tf/øNtf)2 ≤ 1.0

where V*f, Vf, N*tf, Ntf and ø aredescribed above.

See Fig 19 (Grade 4.6) and Fig 20(Grade 8.8) for a plot of the sheartension interaction relationship –strength limit state – for thecommonly used structural bolts.

Ply in Bearing –Strength Limit State

Design provisions for a ply loadedby a bolt in bearing are found inClause 9.3.2.4 of AS 4100-1990.This considers that for a plysubject to a design bearing force(V*b) due to a bolt in shear, thefollowing must be satisfied:

V*b≤øVb

where

ø = 0.9 (Table 3.4 of AS 4100-1990)

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Structural Design UsingBlacks Bolts

Vb = nominal bearing capacity ofa ply

Vb is calculated from the lesser of:

Vb = design bearing capacity dueto ply local bearing failure

= 3.2dftpfup

and

Vb = design bearing capacity dueto plate tearout

= aetpfup

where

df = diameter of the bolt

tp = thickness of the ply

fup = tensile strength of the ply

ae = minimum distance from theedge of a hole to the edge ofa ply, measured in the directof the component of a force,plus half the bolt diameter.The edge of a ply can includethe edge of an adjacent bolthole.

For Grade 4.6 bolting category, forall reasonable combinations of plythickness, bolt diameter and enddistance, the design capacity forply in bearing (øVb) exceeds bothcases of threads included in andexcluded from the shear plane(ie øVf as described above for thebolt in shear – strength limit state).

For the 8.8/S, and 8.8/TB and8.8/TF bolting categories see Table28 for listings of øVb for platetearout and ply local bearingfailure. For further details see Ref[1], [2] and [3] above.

Assessment of theStrength of a BoltGroup

Depending on whether loading isin-plane, out-of-plane and also ifa couple, shear or both act on thebolt group, Clause 9.4 of AS 4100-1990 should be consulted for thedesign of actions on individual orcritically loaded bolts.

SERVICEABILITYLIMIT STATE

The use of a bolted connectionwhich does not slip or has limitedslip under serviceability loadsmay be advisable under certainconditions. This type of connectionis known as a friction-type jointand is identified as 8.8/TF boltingcategory. In AS 4100-1990 theserviceability limit state designprovisions are found in Clause9.3.3. The strength limit state, asmentioned above, should beassessed separately.

Bolt in Shear –Serviceability LimitState

The following inequality must besatisfied for a bolt subjected onlyto a design shear force (V*sf) in the

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F A S T E N E R SStructural Design UsingBlacks Boltsplane of the interfaces forserviceability limit state:

V*sf ≤ ø Vsf

where

ø = 0.7 (Clause 3.5.5 of AS 4100-1990)

Vsf = nominal shear capacity ofbolt, for a friction-typeconnection

= µneiNtikh

where

µ = slip factor

= 0.35 for clean as-rolledsurfaces or determined bytesting in accordance withAppendix J of AS 4100-1990

nei = number of effectiveinterfaces

Nti = minimum bolt tension atinstallation as specified inClause 15.2.5.1 of AS 4100-1990 (see Table 30)

kh = factor for different hole typesas specified in Clause 14.3.5.2of AS 4100-1990

= 1.0 for standard holes

= 0.85 for short slotted andoversize holes

= 0.70 for long slotted holes

The condition of the faying (orcontact) surfaces is of primeimportance, since the slip factor (µ)achieved in practice is directly related tothe condition of the faying surfaces. Theslip factor 0.35 given for designpurposes in AS 4100-1990assumes faying surfaces of baresteel to bare steel – ie in the "as-rolled condition".

Often steel members are painted orgalvanised and it is important toknow what influence this mayhave on the slip factor. Typicalvalues of the slip factor for varioussurface preparations are given inTable 31.

See Table 32 for the listings of boltdesign shear capacity –serviceability limit state (øVsf) – forthe commonly used structuralbolts.

Bolt in Tension –Serviceability LimitState

Not relevant in this limit state.Tension loadings for serviceabilitylimit state are only consideredwhen interacting with shear loadsat serviceability limit state – seebelow.

Bolt Subject toCombined Shear andTension –Serviceability LimitState

For bolts subject simultaneously toshear and tension forces, thefollowing linear interactionrelationship applies:

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Structural Design UsingBlacks Bolts

(V*sf /øVsf)2 + (N*tf /øNtf)2 ≤ 1.0

where V*sf, Vsf and ø are describedabove. For the tension loads:

N*tf = design tension force on thebolt

Ntf = nominal tension capacity ofthe bolt

= Nti

= the minimum bolt tension atinstallation as specified inClause 15.2.5.1 of AS 4100-1990 (see Table 30)

See Fig 21 for a plot of the sheartension interaction relationship –serviceability limit state – for thecommonly used structural bolts.

FATIGUE LIMIT STATE

It is not possible to review here thefatigue provisions of AS 4100-1990Section 11. Reference should bemade to AS 4100 Supplement 1-1990:Steel Structures – Commentary. Insummary, a detail category isassigned to bolted connectionssubject to normal stress (tension)and shear stress. This detailcategory is a number which

corresponds to the fatigue strengthat 2 x 106 cycles on the appropriateS-N curves, a different S-N curvebeing used for each detail category.

For bolts, AS 4100-1990 providestwo detail categories, namely

Detail category 100 bolts inshear, 8.8/TB bolting categorywhere shear stress must becalculated on the core areas, Ac.

Detail category 36 bolts intension, tensile stress beingcalculated on the tensile stress area,As. Additional tension forces dueto prying must be taken intoaccount.

Bolt in Shear –Fatigue Limit State

For shear stress, the uncorrectedfatigue strength (ff) for detailcategory 100 subject to nsc

(number of stress cycles) ofloading or stress is given by

f 5f = (105 x 2 x 106)/nsc

when nsc ≤ 108

This relationship is shown inFig 22.

For bolts subject to shear force, thefatigue provisions of AS 4100-1990(Section 11) gives no guidance for4.6/S and 8.8/S bolting categories.Only 8.8/TF and 8.8/TB arerecommended. As no slip occurswith category 8.8/TF, no separatedesign for fatigue of the bolts isrequired. AS 4100-1990 doescontain design fatigue provisionsfor 8.8/TB bolting category.

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F A S T E N E R SStructural Design UsingBlacks BoltsBolt in Tension –Fatigue Limit State

For normal stress (tension), theuncorrected fatigue strength (ff) fordetail category 36 subject to nsc

cycles of loading or stress is givenby

f 3f = (363 x 2 106)/nsc

when nsc ≤ 5 x 106

f 5f = (365 x 108)/nsc

when 5 x 106 < nsc ≤108

This relationship is shown inFig 22.

For bolts subject to tension force,bolting categories 4.6/S and 8.8/Sare not recommended and 8.8/TFand 8.8/TB are recommended.

Bolt Subject toCombined Shear andTension – FatigueLimit State

AS 4100-1990 does not containdesign provisions for these boltssubject to combined shear andtension under fatigue conditions.

The following reference contains areview of research on fatigue inbolted connections: Guide to DesignCriteria for Bolted and Riveted Joints,Kulak, GL Fisher, JW and Struik,JHA, 2nd Edition, John Wiley 1987.

Design Detail for Bolts

Clause 9.6 of AS 4100-1990 givesthe provisions for design details ofbolts. This includes minimumpitch, minimum edge distance,maximum pitch, and maximumedge distance. Listings of minimumpitch between centres of fastenerholes, and minimum edge distancefrom the centre of a fastener to theedge of a plate or the flange ofrolled section is given in Table33(a) and 33(b) respectively. Notethat minimum edge distancecriteria must also be observedfrom Clause 9.3.2.4 of AS 4100-1990.

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Blacks Structural Bolts

Table 26 Bolt Types and Bolting Categories

Details of bolt used

Minimum MinimumBolting Tensile Yield

Category Strength Strength Strength Australian Method ofGrade (MPa) (MPa) Name Standard Tensioning Remarks

4.6/S 4.6 400 240 Commercial AS 1111 Use Snug tightened.Least costly and mostcommonly available4.6 Grade bolt.

8.8/S 8.8 830 660 High AS 1252 Bolts used are SnugStrength tightened. The highStructural strength structural has a

large bolt head and nutbecause it is designed towithstand full tensioning(see 8.8T categorydescription). However, itcan also be used in asnug tight condition.

8.8/TF 8.8 830 660 High AS 1252 In both applications boltsStrength are fully Tensioned toStructural the requirements of

Bolt – Fully AS4100. Cost of tension-8.8/T Tensioned ing is an important con-

Friction sideration in the use ofType Joint these bolting categories.

8.8/TB 8.8 830 660 HighStrengthStructural

Bolt – FullyTensionedBearing

Type Joint

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Blacks Structural Bolts F A S T E N E R S

Table 27 Design Shear and Tension Capacities – Strength Limit StateCommercial Bolts 4.6/S Bolting Category(fuf = 400 MPa) Grade 4.6

Shear Values (Single Shear)

Bolt Axial Threads included Threads excludedSize Tension in Shear Plane – N from Shear Plane – X

ø Ntf ø Vfn ø Vfx

kN kN kN

M12 27.0 15.1 22.4

M16 50.2 28.6 39.9

M20 78.4 44.6 62.3

M24 113 64.3 89.7

M30 180 103 140

M36 261 151 202

ø = 0.8ø = 0.8

4.6N/S 4.6X/S

NOTE 1.Bearing/Plate Tearout Design Capacity. For all reasonable combinations of plythickness, bolt diameter and end distance, the design capacity for a ply inbearing (ØVb) exceeds both ØVfn and ØVfx.

Table 28 Design Shear and Tension Capacities – Strength Limit StateHigh Strength Structural Bolts8.8/S 8.8/TB 8.8/TF Bolting Categories(fuf = 400 MPa) Grade 8.8

Single Shear Plate Tearout Bearing

Bolt Axial Threads ThreadsSize Tension included excluded øVb for tp & ae of: øVb for tpf

in fromShear ShearPlane Plane

øNtf øVfn øVfx tp = 6 tp = 8 tp = 10 tp = 12

kN kN kN 35 40 45 35 40 45 35 40 45 35 40 456 8 10

M16 104 59.3 82.7 113 151 189

M20 163 92.6 129 79 89 100 103 118 133 129 148 166 155 177 199 142 189 236

M24 234 133 186 170 227 283

M30 373 214 291 213 283 354

ae < aemin = 1.5 df

ø = 0.8 ø = 0.9 ø = 0.9ø = 0.8

8.8N/S 8.8X/S fup = 410 MPa fup=410MPa

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Table 29 Reduction factor for lap connections (kr)

Length Lj < 300 300 ≤ Lj ≤ 1300 Lj > 1300

kr 1.0 1.075 – Lj/4000 0.75

Table 30 Minimum bolt tension atinstallation

Nominal Minimum BoltDiameter of Tension

Bolt kN

M16 95

M20 145

M24 210

M30 335

M36 490

Table 31 Summary of Slip Factors

Surface AverageTreatment Slip Factor

UncoatedClean as-rolled 0.35Flame cleaned 0.48Abrasive blasted 0.53

PaintedRed oxide zinc chromate 0.11Inorganic zinc silicate 0.50

Hot-dip GalvanisedClean as-galvanised 0.18Lightly abrasive blasted 0.30-0.40

NOTE: The minimum bolt tensionsgiven in this Table are approximatelyequivalent to the minimum proof loadsgiven in AS 1252.

Table 32 Design Shear Capacity – Serviceability Limit StateHigh Strength Structural Bolts 8.8/TF Bolting Category(µ = 0.35 nei = 1 ø = 0.7) Grade 8.8

Bolt Bolt Tension Design Capacity in Shear (øVsf) forSize at Installation kh = 1 kh = 0.85 kh = 0.7

kN kN kN kN

M16 95 23.3 19.8 16.3

M20 145 35.5 30.2 24.9

M24 210 51.5 43.7 36.0

M30 335 82.1 69.8 57.5

Lj = length of a bolted lap splice connection.

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Blacks Structural Bolts F A S T E N E R S

Blacks High StrengthStructural Bolts

Table 33a Minimum Pitchbetween Centres of FastenerHoles (Clause 9.6.1 of AS 4100-1990)

Minimum distanceBolt between centres ofsize fastener holes mm

M12 30

M16 40

M20 50

M24 60

M30 75

M36 90

NOTE: The edge distance mayalso be affected by Clause 9.3.2.4of AS 4100-1990

Table 33b Minimum Edge Distance (Clause9.6.2 of AS 4100-1990)

Sheared or Rolled Plate;Hand Flame Machine Rolled Edge

Bolt Cut Edge Flame Cut of a RolledSize Sawn or Section

Planed Edge(mm) (mm) (mm)

M12 21 18 15

M16 28 24 20

M20 35 30 25

M24 42 36 30

M30 53 45 38

M36 63 54 45

NOTE: The edge distance may also beaffected by Clause 9.3.2.4 of AS 4100-1990

Property Class 8.8Thread ISO Metric CoarsePitch SeriesDimensions to AS 1252

Table 34

Bolt Dimensions Nut Dimensions

Pitch Width Width Width ThicknessSize of Body Dia. Across Across Head Across

Thread Flats Corners Thickness FlatsD D1 s e k s m

Max. Min. Max. Min. Min. Max. Min. Max. Min. Max. Min.

M16 2.0 16.70 15.30 27 26.16 29.56 10.75 9.25 27 26.16 17.1 16.0

M20 2.5 20.84 19.16 32 31.00 35.03 13.90 12.10 32 31.00 21.3 20.0

M24 3.0 24.84 23.16 41 40.00 45.20 15.90 14.10 41 40.00 25.3 24.0

M30 3.5 30.84 29.16 50 49.00 55.37 19.75 17.65 50 49.00 31.3 30.0

M36 4.0 37.00 35.00 60 58.80 66.44 23.55 21.45 60 58.80 37.6 36.0

All dimensions in millimetres.

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Blacks High StrengthStructural Bolts

(Flat Round Washers)

Standard Thread Length for Bolts

Nominal Length of Bolt I Nominal Length of Thread b

Up to and including 125mm 2D + 6mm

Over 125 up to and including 200mm 2D + 12mm

Over 200mm 2D + 25mm

Table 35 Dimensions of Flat Round Structural Washers

Nominal Inside Diameter Outside Diameter ThicknessDiameter D1 D2 Aof Bolt Max. Min. Max. Min. Max. Min.

M16 18.43 18.0 34.0 32.4 4.60 3.1

M20 22.52 22.0 39.0 37.4 4.60 3.1

M24 26.52 26.0 50.0 48.4 4.60 3.4

M30 33.62 33.0 60.0 58.1 4.60 3.4

M36 39.62 39.0 72.0 70.1 4.60 3 4

All dimensions in millimetres.

Blacks High StrengthStructural Bolts

(Square Taper Washers)

Table 36 Dimensions of Square Taper Washers

Inside Diameter Width Across Mean ThicknessNominal FlatsDiameter D1 D2 Aof Bolt Max. Min. Nominal 5° Taper 8° Taper

M16 18.43 18.0 31.75 4.76 6.35

M20 22.52 22.0 38.10 4.76 6.35

M24 26.52 26.0 44.45 4.76 6.35

All dimensions in millimetres.

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Coronet Load Indicators F A S T E N E R S

Coronet Load indicators aredesigned for use with Blacks highstrength structural bolts and theyprovide a simple and accurate aidto tightening and inspection. Theycan be supplied with galvanisedcoating for good corrosionresistance.

The Load Indicators are specialhardened washers carrying 4 to 7protrusions, depending on boltdiameter (Figure 27) and these areassembled with the protrusionsbearing against the under side ofthe bolt head, leaving a gap. Thenut is then tightened until theprotrusions are flattened and thegap reduced to that shown inTable 37. The induced bolt tensionat this average gap will be not lessthan the minimum specifiedtension in Table 38. In applicationswhere it is necessary to rotate thebolt head rather than the nut intightening, the Coronet LoadIndicator can be fitted under the

nut using an extra hard roundwasher under the nut andprotrusions bear against thiswasher (Figure 29). In tighteningwith Load Indicators it is stillrequired that this tightening becarried out in two stages. Firststage involves a preliminarytightening to a "snug tight"condition using a podger spanneror pneumatic impact wrench. Theobject of the preliminarytightening is to draw the matingsurfaces into effective contact. Onlarge joints take a second run toensure that all the bolts are "snugtight". Carry out final tightening byreducing gap between bolt headand load indicator to 0.40mm orless and this can be checked with afeeler gauge.

MOST IMPORTANT: A nutshould not be slackened after fullytightening with a Load Indicator. Ifthis is necessary, fit a new LoadIndicator for the second tightening.

For direct tension indicationtightening of Blacks FastenersHigh Strength Structural BoltsAS 1252.

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Coronet Load IndicatorsF A S T E N E R S

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For direct-tension indicationtightening of Blacks FastenersHigh Strength Structural BoltsAS 1252.

Table 37Load indicator gaps to give required minimum shank tension

Load Indicator Fitting AS 4100 (1511)

Under bolt head black finish bolts 0.4mm

All plating except galvanised bolts 0.4mm

Galvanised bolts 0.25mm

Under nut with hard flat washer, black andall flat washer coatings 0.25mm

Table 38Load indicator gaps to give required minimum shank tension

Nominal Outside Inside Thickness MinimumBolt Diameter Diameter A Bolt Tension

Diameter D2 D1 Max. kN

M16 35.45 16.70 4.26 100

M20 41.67 20.84 4.26 150

M24 50.69 24.84 4.26 220

M30 59.59 30.84 4.26 350

M36 80.00 37.50 4.26 515

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F A S T E N E R SUnified High TensileHexagon BoltsThreads, UNC, UNF, Class 2ADimensions to ANSI/ASMEB18.2.1Finished Hexagon BoltsAS 2465

Table 39

Threads Body Width Head Across ThreadSize per Diameter Across Flats thickness Corners Length

inch A B C TUNF UNC Max. Min. Nom. Max. Min. Max. Min. Max. Min.

1/4 28 20 .250 .245 7/16 .438 .428 .163 .150 .505 3/4

5/16 24 18 .3125 .3065 1/2 .500 .489 .211 .195 .577 7/8

3/8 24 16 .3750 .3690 9/16 .562 .551 .243 .226 .650 1

7/16 20 14 .4375 .4305 5/8 .625 .612 .291 .272 .722 11/8

1/2 20 13 .5000 .4930 3/4 .750 .736 .323 .302 .866 11/4

9/16 18 12 .5625 .5545 13/16 .812 .798 .371 .348 .938 13/8

5/8 18 11 .6250 .6170 15/16 .938 .922 .403 .378 1.083 11/2

3/4 16 10 .750 .741 11/8 1.125 1.100 .483 .455 1.299 13/4

7/8 14 9 .875 .866 15/16 1.312 1.285 .563 .531 1.516 2"

1 12 8 1.000 .990 11/2 1.500 1.469 .627 .591 1.732 21/4

11/8 12 7 1.125 1.114 111/16 1.688 1.631 .718 .658 1.949 21/2

11/4 12 7 1.250 1.239 17/8 1.875 1.812 .813 .749 2.165 23/4

11/2 12 6 1.500 1.488 21/4 2.250 2.175 .974 .902 2.598 31/4

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F A S T E N E R S

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Unified Hexagon Head Set Screws

– High Tensile

Threads, UNC, UNF,Dimensions to ANSI/ASMEB18.2.1 AS 2465

Table 40

Threads Head Head Head RadiusSize per Across Flats Depth Across Corners Under Head

inch A B C R

UNF UNC Max. Min. Max. Min. Max. Min. Max. Min.

1/4 28 20 .438 .428 .163 .150 .505 .488 .025 .0155/16 24 18 .500 .489 .211 .195 .577 .557 .025 .0153/8 24 16 .562 .551 .243 .226 .650 .628 .025 .0157/16 20 14 .625 .612 .291 .272 .722 .698 .025 .015

NOTE: Set Screws shall be threaded to within 21/2 pitches of the underside of thehead.

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F A S T E N E R SMetric Hexagon PrecisionBolts & Set Screws

Table 41

Pitch Body Width Across Head AcrossSize of Diameter Flats Thickness Corners

Thread Ds s k e

D Max. Min. Max. Min. Max. Min. Min.

M5 0.8 5.0 4.82 8.0 7.78 3.65 3.35 8.79

M6 1.0 6.0 5.82 10.0 9.78 4.15 3.85 11.06

M8 1.25 8.0 7.78 13.0 12.73 5.45 5.15 14.38

M10 1.5 10.0 9.78 16.0 15.73 6.58 6.22 17.77

M12 1.75 12.0 11.73 18.0 17.73 7.68 7.32 20.03

M16 2.0 16.0 15.73 24.0 23.67 10.18 9.82 26.75

M20 2.5 20.0 19.67 30.0 29.67 12.72 12.28 33.53

M24 3.0 24.0 23.67 36.0 35.38 15.22 14.78 39.98

All dimensions in millimetres.

Table 42 Standard thread lengths for bolts.Screws are threaded to head.

Nominal Length of Bolt I Minimum Length of Thread b

Up to and including 125mm 2D + 6mm

Over 125 up to and including 200mm 2D + 12mm

Over 200mm 2D + 25mm

Where D = Nominal diameter in millimetresNote: Property Classes 5.8 and 10.9 are dimensionally the same as PropertyClass 8.8

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Metric Hexagon CommercialBolts & Set Screws

Table 43

Pitch Body Diameter Width Across Head AcrossSize of (On Bolts) Flats Thickness Corners

Thread Ds s k e

D Max. Min. Max. Min. Max. Min. Min.

M6 1.0 6.48 5.52 10.0 9.64 4.38 3.62 10.89

M8 1.25 8.58 7.42 13.0 12.57 5.68 4.92 14.20

M10 1.5 10.58 9.42 16.0 15.57 6.85 5.95 17.59

M12 1.75 12.70 11.30 18.0 17.57 7.95 7.05 19.85

M16 2.0 16.70 15.30 24.0 23.16 10.75 9.25 26.17

M20 2.5 20.84 19.16 30.0 29.16 13.40 11.60 32.95

M24 3.0 24.84 23.16 36.0 35.00 15.90 14.10 39.55

M30 3.5 30.84 29.16 46.0 45.00 19.75 17.65 50.85

M36 4.0 37.00 35.00 55.0 53.80 23.55 21.45 60.79

All dimensions in millimetres.

Table 44 Standard thread lengths for bolts. Screws are threaded to head

Nominal Length of Bolt I Minimum Length of Thread b

Up to and including 125mm 2D + 6

Over 125mm up to and including 200mm 2D + 12

Over 200mm 2D + 25

Where D = Nominal diameter in millimetresFor nut dimensions refer to page 14

Thread ISO Metric Coarse PitchSeries, Thread Class 8g,Property Class 8.8Dimensions to AS 1111

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Hexagon Head Bolts F A S T E N E R S

Table 45

Threads Body Head Head Across RadiusSize per Diameter Across Flats Depth Corners Under Head

inch s k e R

Max. Max. Min. Max. Min. Max. Max. Min.

1/4 20 .280 .445 .435 .186 .166 .51 .031 .0215/16 18 .342 .525 .515 .228 .208 .61 .031 .0213/8 16 .405 .600 .585 .270 .250 .69 .031 .0217/16 14 .468 .710 .695 .312 .292 .82 .031 .0211/2 12 .530 .820 .800 .363 .333 .95 .031 .021 5/8 11 .665 1.010 .985 .447 .417 1.17 .046 .0363/4 10 .790 1.200 1.175 .530 .500 1.39 .046 .0367/8 9 .915 1.300 1.270 .623 .583 1.50 .062 .052

1 8 1.040 1.480 1.450 .706 .666 1.71 .062 .052

Threads BSW Free Class Dimensions to AS 2451

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Hexagon Head Set ScrewsF A S T E N E R S

Fasteners your guarantee of quality industrial fasteners

Threads BSW Free ClassDimensions to AS 2451

Table 46

Threads Head Head Head RadiusSize per Across Flats Depth Across Under Head

inch Cornerss k e

Max. Min. Max. Min. Max. Min. Min.

1/4 20 .445 .435 .186 .166 .51 .031 .0215/16 18 .525 .515 .228 .208 .61 .031 .0213/8 16 .600 .585 .270 .250 .69 .031 .0217/16 14 .710 .695 .312 .292 .82 .031 .0211/2 12 .820 .800 .363 .333 .95 .031 .0215/8 11 1.010 .985 .447 .417 1.17 .046 .0363/4 10 1.200 1.175 .530 .500 1.39 .046 .0367/8 9 1.300 1.270 .623 .583 1.50 .062 .052

1 8 1.480 1.450 .706 .666 1.71 .062 .052

NOTE: Set screws shall be threaded to within 21/2 pitches of the underside of thehead.

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F A S T E N E R S

Table 47 Metric Series Cup Square Bolts

Nom. Pitch Diameter of Body AcrossSize of Reduced Full Flats of Length Head Headand Thread Body Body Square of Square Diameter Thickness

Thread D1 D2 Neck NeckDia. V f D3 k

Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min.

M6 1.0 5.2 6.48 5.52 6.48 5.52 3.6 3.0 13.5 12.4 3.6 3.0

M8 1.25 7.0 8.58 7.42 8.58 7.42 4.8 4.0 18.0 16.9 4.8 4.0

M10 1.50 8.8 10.58 9.42 10.58 9.42 5.8 5.0 22.5 21.2 5.8 5.0

M12 1.75 10.6 12.70 11.30 12.70 11.30 6.8 6.0 27.0 25.7 6.8 6.0

M16 2.0 14.5 16.70 15.30 16.70 15.30 8.9 8.0 36.0 34.4 8.9 8.0

M20 2.5 18.1 20.84 19.16 20.84 19.16 10.9 10.0 45.0 43.4 10.9 10.0

Metric Cup HeadSquare Neck BoltsThreads ISO Metric CoarsePitch SeriesDimensions to AS 1390

For nut dimensions refer to page 14

Standard Thread Length for Bolts

Nominal Length of Bolt / Minimum Length of Thread b

M5 M6 M8 M10 M12 M16 M20 M24

Up to and including 125mm 16 18 22 26 30 38 46 54

Over 125 up to and including 200mm 22 24 28 32 36 44 52 60

Over 200mm – – 41 45 49 57 65 73

Maximum thread length shall not exceed 80mmMechanical Properties:Tensile Strength = 400 MPa (N/mm2) minimum

= 58,000 lbf/in2 minimum= 25.9 tonf/in2 minimum

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Cup Head Square Neck BoltsF A S T E N E R S

Fasteners your guarantee of quality industrial fasteners

Table 48

Threads Head Head Depth WidthSize per Diameter Thicknes of Square of Square

inch A B C W

Max. Min. Max. Min. Max. Min. Max. Min.

3/16 24 .451 .391 .113 .093 .125 .094 .197 .1831/4 20 .592 .532 .145 .125 .156 .125 .260 .2455/16 18 .733 .673 .176 .156 .187 .156 .323 .3073/8 16 .873 .813 .207 .187 .219 .188 .388 .3687/16 14 1.014 .954 .238 .218 .250 .219 .451 .4311/2 12 1.155 1.095 .270 .250 .281 .250 .515 .492

For nut dimensions refer to page 14

Threads BSW Free ClassDimensions to AS B108

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F A S T E N E R SCoach Screws – HexagonHead Metric Series

Table 49 Metric Series Coach Screws

Pitch Body Width Width Head Root Dia.Nom. of Diameter Across Across Thickness ofSize Thread Flats Corners Thread

D s e k dsmm Max. Min. Max. Min. Min. Max. Min. Max. Min.

6 2.5 6.48 5.52 10.0 9.64 10.89 4.38 3.62 4.4 3.7

8 3.0 8.58 7.42 13.0 12.57 14.20 5.88 5.12 5.6 5.0

10 3.5 10.58 9.42 17.0 16.57 18.72 7.45 6.55 7.0 6.2

12 4.0 12.70 11.30 19.0 18.48 20.88 8.45 7.55 8.3 7.5

16 5.0 16.70 11.30 24.0 23.16 26.17 10.45 9.55 12.7 11.3

20 5.0 20.84 19.16 30.0 29.16 32.95 13.90 12.10 15.6 14.2

Mechanical Properties

Tensile Strength = 400MPa (N/mm2) minimum= 58,000 lbf/in2 minimum= 25.9 tonf/in2 minimum

Dimensions to AS 1393

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Elevator Bolts Four PegF A S T E N E R S

Fasteners your guarantee of quality industrial fasteners

Threads BSW Free Class

Table 51

Size Threads Head Head Pitch Dia. Length Angleper Diameter Depth of Pegs of Peg Under HeadInch A B C D E

Max. Min. Max. Min. Max. Min. Max. Min. Max. Min.

1/4 20 .697 .667 .120 .100 .510 .490 .156 .136 17° 13°5/16 18 .859 .829 .160 .140 .635 .615 .194 .174 22° 18°3/8 16 1.077 1.047 .194 .174 .760 .740 .237 .217 24° 20°

Mechanical Properties

Tensile Strength = 28 tonf/in2.Supplied with nut and washer.

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Metric Hexagon Nuts F A S T E N E R S

Threads ISO Metric CoarsePitch Series. Class 6H.These nuts are stocked inProperty Class 8 M5 to M16 incl;Property Class 5 M20-M64 incl.

Table 52

Pitch Width Across Width Across ThicknessSize of Flats Corners Standard Nut Thin Nut

Thread s e m t

Max. Min. Max. Min. Max. Max. Min.

M5 0.8 8.0 7.78 8.79 4.70 4.40 3.0 2.75

M6 1.0 10.0 9.78 11.05 5.20 4.90 3.6 3.30

M8 1.25 13.0 12.73 14.38 6.80 6.44 4.8 4.50

M10 1.50 16.0 15.73 17.77 8.40 8.04 6.0 5.70

M12 1.75 18.0 17.73 20.03 10.80 10.37 7.2 6.84

M16 2.0 24.0 23.67 26.75 14.80 14.10 9.6 9.02

M20 2.5 30.0 29.16 32.95 18.00 16.90 12.0 11.30

M24 3.0 36.0 35.00 39.55 21.50 20.20 14.4 13.70

M27 3.0 41.0 40.00 45.20 23.80 22.50 16.2 15.50

M30 3.5 46.0 45.00 50.85 25.60 24.30 18.0 17.30

M33 3.5 50.0 49.00 55.37 28.70 27.40 19.8 18.96

M36 4.0 55.0 53.80 60.79 31.00 29.40 21.6 20.76

M39 4.0 60.0 58.10 65.65 33.40 31.80 23.4 22.56

M42 4.5 65.0 63.10 71.30 34.8 33.20 25.2 24.36

M48 5.0 75.0 73.10 82.60 38.8 37.20 28.8 27.96

M56 5.5 85.0 82.80 93.56 45.8 44.20 – –

M64 6.0 95.0 92.80 104.86 52.0 50.10 – –

All dimensions in millimetres.

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F A S T E N E R S

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Hexagon Nuts & Hexagon Lock Nuts

Threads BSWDimensions to AS 2451* up to 15/8"*Hexagon nuts only

Table 53

Threads Width Across Width Across ThicknessSize per Flats Corners Nuts Lock Nut

inch s e m t

Max. Min. Max. Min. Max. Max. Min.

3/16 24 .324 .319 .37 .167 .1571/4 20 .445 .435 .51 .220 .200 .185 .1805/16 18 .525 .515 .61 .270 .250 .210 .2003/8 16 .600 .585 .69 .332 .312 .260 .2507/16 14 .710 .695 .82 .395 .375 .275 .2651/2 12 .820 .800 .95 .467 .437 .300 .2909/16 12 .920 .900 1.06 .530 .500 .330 .3235/8 11 1.010 .985 1.17 .602 .562 .410 .3753/4 10 1.200 1.175 1.39 .728 .687 .490 .4587/8 9 1.300 1.270 1.50 .810 .750 .550 .500

1 8 1.480 1.450 1.71 .935 .875 .630 .583

11/8 7 1.670 1.640 1.93 1.060 1.000 .720 .666

11/4 7 1.860 1.815 2.15 1.205 1.125 .810 .750

13/8 6 2.050 2.005 2.37 1.330 1.250 .890 .833

11/2 6 2.220 2.175 2.56 1.455 1.375 .980 .916

15/8 5 2.410 2.365 2.78 1.580 1.500 1.060 1.000

13/4 5 2.580 2.520 2.98 1.625 1.565 1.160 1.083

2 4.5 2.760 2.700 3.19 1.750 1.690 1.250 1.166

21/4 4 3.150 3.090 3.64 1.875 1.815 1.430 1.250

21/2 4 3.550 3.490 4.10 2.125 2.065 1.600 1.416

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F A S T E N E R SUnified Hexagon Nuts &Hexagon Lock Nuts

Threads UNC, UNF, Class 2BDimensions to ANSI/ASME B18.2.2AS 2465

Table 54

Across Across ThicknessThreads Flats Corners Approx Wt.

Dia. per F G Standard H Jam Nut T lbs per 100Inch Max. Min. Max. Min. Max. Min. Max. Min. Std. Jam

1/420 UNC

.438 .428 .505 .488 .226 .212 .163 .150 .753 .51528 UNF

5/1618 UNC

.500 .489 .577 .557 .273 .258 .195 .180 1.10 .76724 UNF

3/816 UNC

.562 .551 .650 .628 .337 .320 .227 .210 1.60 1.0524 UNF

7/1614 UNC

.688 .675 .794 .768 .385 .365 .260 .240 2.84 1.8620 UNF

1/213 UNC

.750 .736 .866 .840 .448 .427 .323 .302 3.75 2.6220 UNF

9/1612 UNC

.875 .861 1.010 .982 .496 .473 .324 .301 5.83 3.6818 UNF

5/811 UNC

.938 .922 1.083 1.051 .559 .535 .387 .363 7.33 4.9318 UNF

3/410 UNC

1.125 1.088 1.299 1.240 .665 .617 .446 .398 11.9 7.7016 UNF

7/89 UNC

1.312 1.269 1.516 1.447 .776 .724 .510 .458 19.0 12.014 UNF

18 UNC

1.500 1.450 1.732 1.653 .887 .831 .575 .519 28.3 17.612 UNF

Table 55 Mechanical Properties (Hexgaon Nuts)

Size Range Strength Specifications Thread "Proof Load" Stress lbf/in2

Up to and including 5/8" SAE Grade 5 UNC 120,000

ASTM: A563 Grade B UNF 109,0003/4" to 1" inclusive SAE Grade 2 UNC 90,000

ASTM: A563 Grade A UNF 90,000

Nuts to other specifications (eg SAE Grade 8) or SAE Grade 5 in. 3/4 – 11/2" canbe quoted against enquiries.

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Fasteners your guarantee of quality industrial fasteners

Table 56 Dimensions, except those with asterisk, comply to AS 1258

s e h m h mPitch Across Across P TYPE T TYPE

Nom. of Flats Corners Nut Thread Nut ThreadDia. Thread Height Height Height Height

Max. Min. Max. Min. Max. Min. Max. Min.

M4 0.7 7.00 6.78 8.10 7.66 5.0 2.90 – –

M5 0.8 8.00 7.78 9.20 8.79 6.3 4.0 – –

M6 1.0 10.00 9.78 11.50 11.05 8.0* 5.0 6 4

M8 1.25 13.00 12.73 15.00 14.38 9.5 6.5 8 5.5

M10 1.5 17.00 16.73 19.60 18.90 11.5 8.0 10 6.5

M12 1.75 19.00 18.67 21.90 21.10 14.0 10.0 12 8

M16 2.0 24.00 23.67 27.70 26.75 18.0 13.0 16 10.5

M20 2.5 30.00 29.16 34.60 32.95 22.0 16.0 19.85 9.42

M24 3.0 36.00 35.00 41.60 39.55 28.0 20.2 22.02 11.30

M30 3.5 46.00 45.00 53.10 50.85 36.0 23.30 20.20 14.30

M36 4.0 55.00 53.80 63.50 60.79 43.2 28.30 24.50 17.30

M42* 4.5 65.00* 63.80* 75.10* 72.09* 50.5* 33.20* 28.90* 20.20*

M48* 5.0 75.00* 73.10* 86.60* 82.60* 57.5* 37.20* 32.90* 23.15*

Mechanical Properties:P Type M4-M24 Proof Load Stress 800 MPa AS 1285 P.C.8P Type M30-M36 Proof Load Stress 400 MPa –T Type M6-M16 Proof Load Stress 600 MPa AS 1285 P.C.6T Type M2G-M36 Proof Load Stress 400 MPa –

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Nyloc Nuts BSW F A S T E N E R S

Table 57

s e h m h mThreads Across Across P TYPE T TYPE

Nom. per Flats Corners Nut Thread Nut ThreadDia. inch Height Height Height Height

Max. Min. Max. Max. Min. Max. Min.

3/16 24 .324 .319 .374 .267 .156 – –1/4 20 .445 .435 .510 .321 .190 .254 .1235/16 18 .525 .515 .610 .378 .240 .294 .1563/8 16 .600 .585 .690 .438 .302 .333 .1987/16 14 .710 .695 .820 .528 .365 .403 .2401/2 12 .820 .800 .950 .593 .427 .447 .2815/8 11 1.010 .985 1.170 .722 .552 .535 .3653/4 10 1.200 1.175 1.390 .960 .677 .731 .4487/8 9 1.300 1.270 1.500 1.012 .740 .762 .490

1 8 1.480 1.450 1.710 1.113 .865 .821 .573

11/8 7 1.670 1.640 1.930 1.239 .990 .905 .656

11/4 7 1.860 1.815 2.150 1.440 1.105 1.065 .730

11/2 6 2.220 2.175 2.560 1.734 1.355 1.274 .896

13/4 5 2.580 2.520 2.980 1.985 1.605 1.450 1.063

2 4.5 2.760 2.700 3.190 2.125 1.730 1.565 1.146

Mechanical Properties:P Type Proof Load Stress 28 tonf/in2 (432 MPa) AS 2451T Type Proof Load Stress 14 tonf/in2 (216 MPa)

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Nyloc Nuts YNC/UNFF A S T E N E R S

Fasteners your guarantee of quality industrial fasteners

Table 58

s e h m h mThreads Across Across P TYPE T TYPE

Nom. per inch Flats Corners Nut Hex Nut HexDia. UNC Height Height Height Height

UNF Max. Min. Max. Max. Ref. Max. Ref.

1/4 20 .439 .430 .488 .328 .225 .240 .12828

5/1618 .502 .492 .557 .359 .250 .265 .15824

3/8 16 .564 .553 .628 .468 .335 .348 .22024

7/1614 .627 .615 .698 .468 .324 .328 .22520

1/2 13 .752 .741 .840 .609 .464 .328 .19020

9/1612 .877 .865 .982 .656 .469 – –18

5/8 11 .940 .928 1.051 .765 .593 .406 .26518

3/4 10 1.064 1.052 1.191 .890 .742 .421 .28816

7/8 9 1.312 1.269 1.447 1.022 .758 .484 .34014

1 8 1.500 1.450 1.615 1.098 .858 .578 .40512

11/8 7 1.688 1.631 1.826 1.224 .949 – –12

11/4 7 1.875 1.812 2.038 1.365 1.040 .765 .52312

11/2 6 2.250 2.175 2.416 1.618 1.255 .828 .56512

13/4 5 2.750 2.662 3.035 2.052 1.689 1.302 .93912

2 4.5 3.125 3.025 3.449 2.367 1.935 1.492 1.06012

Mechanical Properties:UNC P Type 1/4" – 3/4" Proof Load Stress 120,000 tonf/in2 (827 MPa) AS 2465 G5UNC P Type 7/8" – 2" Proof Load Stress 90,000 tonf/in2 (621 MPa) AS 2465 G2UNF P Type 1/4" – 3/4" Proof Load Stress 109,000 tonf/in2 (952 MPa) AS 2465 G5UNF P Type 7/8" – 2" Proof Load Stress 90,000 tonf/in2 (621 MPa) AS 2465 G2UNC T Type 1/4" – 11/2" Proof Load Stress 72,000 tonf/in2 (496 MPa)UNC T Type 1/4" – 11/2" Proof Load Stress 165,000 tonf/in2 (448 MPa)

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F A S T E N E R SCorrect Use ofJam or Lock Nuts

When a Jam or Lock Nut is to beused, it should always be placed asshown in Fig 49, not as in Fig 48.

The lock nut must always beassembled on the bolt first andpulled up snug, but not tightenedseverely enough to produce a hightension in the bolt.

The top nut is then assembled, andas it is tightened the threads of thelock nut must first bear upward onthe bolt threads, then are free, andfinally bear downward on the boltthreads, while the threads of thetop nut bear upwards on the boltthreads.

Thus the two nuts are bearing inopposite directions on the threadsand are jammed.

This locking effect will remain evenif the bolt tension is lost.

The final bolt tension is thereforehigher than that originally set upby the bottom nut, and may in factbe higher than could be sustainedby the bottom nut alone, sincemost of the tension is now beingsupplied by the top nut.

Conclusion

The bottom nut should be the Jamor Lock Nut. It should not have atight thread fit. It should be appliedwith only moderate initial torque.The top nut should be wrenchedon the full torque requirements.During final wrenching, thebottom nut should be held fromturning.

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Corrosive Protective CoatingsF A S T E N E R S

Fasteners your guarantee of quality industrial fasteners

Acknowledgement is made to theAmerican Industrial FastenersInstitute for information in thisarticle

Corrosion ProtectiveCoating

Approximately 90% of all carbonsteel fasteners are plated, coated orfurnished with some other type ofsupplementary finish. Althoughthe principal reason is to protectagainst corrosion, such treatmentsalso enhance appearance, controlinstallation torque-tensionrelationships, minimise threadseizing, and assist productidentification.

Coating

Coatings are adherent layersapplied to the surface of a basemetal. For commerical fasteners,practically all deposition isaccomplished by electroplating,hot-dipping or mechanically.Other processes such as sprayingmolten metal, vacuum metalising,chemical vapour deposition, ionplating, enameling and dip andbake are special purpose andeconomically impractical for stockcommercial fasteners.

Metallic Coatings

Zinc is by far the most widely usedplated metal followed inpopularity by cadmium andaluminium, which has modest use.Copper, tin, nickel, chromium, leadand silver are used to a lesserdegree – all for special reasons.

ZincZinc is favoured as a plating metalbecause in the Galvanic Series it isless noble than carbon steel,stainless steel and most othernonferrous metals used in fastenerapplications. In an electrochemicalreaction, the plating metalcorrodes, and through its sacrifice,the base metal remains protected.Only after the plating metal hasbeen significantly lost to corrosiondoes corrosion of the base metalbegin. Other plating metals aremore noble than carbon steel.When the base coating is breached,the base metal comes underimmediate attack.

Zinc is the popular fastener coatingalso because it is the leastexpensive, has good appearance,can be applied in a broad range ofthickness, by self passivation hasgood-to-excellent corrosionresistance, and is relatively non-toxic. Zinc plated fasteners mayrequire more tightening torque todevelop equivalent preloads inthreaded fasteners. Also zinccoatings without somesupplementary protection developa dull white corrosion product ontheir surface which is nicnamed"white rust". Because of itsunsightly appearance, most zincplated fasteners are givenchromate treatment, which is achemical conversion process tocover the zinc surface with a hardnon-porous film. This addedcoating effectively seals the surface,protects it against early tarnishing,and reinforces the fastener'sresistance to corrosion attack.Chromate coatings are availableclear, iridescent, or in a variety ofcolours.

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Corrosive Protective Coatings F A S T E N E R S

Plating Thickness

As a general rule, fastener servicelife, in a corrosive atmosphere, isproportional to the thickness of itsplating. The thicker the plating thelonger it will survive.

Electroplated fasteners haveplating thicknesses ranging from a"flash" coating of insignificantthickness to a "commerical"thickness of 0.0002in. 5µm,through to 0.0005in. 12µm. Thickerelectroplatings are possible but,from an economics viewpoint,quite impractical.

Hot-dip galvanising producesmuch thicker coatings, which inengineering standards areexpressed in terms of mass ofplating metal deposited per unitarea of a coated surface. Standardhot-dip galvanised fasteners havean average thickness coating of.002/in2 (50µm in thickness).Heavier coatings to .003 (80µm) arefeasible, but such coatings maynecessitate adjustments in matingthread fits to a degree that thefastener's strength properties maybe adversely affected.

Mechanically plated coatingthicknesses are available throughthe full range offered by eitherelectroplating or hot-dipgalvanising.

Life Expectancy

For several years, the relativecorrosion combating performanceof zinc electroplated and hot-dipgalvanised fasteners comparedwith mechanically plated fastenershas been under investigation. A

range of exposure environmentsindicated equivalent performancesfor fasteners having the samecoating thickness.

Useful service life expectancies ofzinc plated fasteners in variousenvironments are:

Zinc plated with chromate treatment,0.0005in plating thickness: up to 20years indoors, about 4 years in a ruralatmosphere, 2 years in coastallocations and less than 1 year inheavily polluted industrialatmosphere.

Hot-dipped galvanised with anaverage thickness of 0.002in over 40years in a rural atmosphere, 25-30years in coastal locations and 5 yearsor longer in heavily polluted industrialatmosphere.

Survivability is almost a directfunction of coating thickness.However, plating is expensive.Costs – and attendant problems –increase with increasing platingthickness. Consequently, theprudent engineer is advised tospecify only that thickness ofplating required to satisfy theapplication.

Plating Distribution

The build up of plating on fastenersurfaces occurs differently witheach of the principal depositionmethods.

Electroplating deposits the platingmetal unevenly with exterior edgesand corners receiving thickercoatings. In the fastener's threadedsection, the thickest plating islocated at the thread crests andbecomes progressively thinner on

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the thread flanks, with the thinnestdeposits in the thread roots. Withhot-dip galvanising, it is just theopposite, with thicker coatingsdeposited at interior corners and inthe thread roots. Because cloggingof thread roots is difficult tocontrol, it is usually impactical tohot-dip galvanise fasteners ofnominal sizes smaller than M10(3/8"). Mechanical plating tends todeposit the plating metal similarlyto hot-dip galvanising but moresmoothly and considerably moreuniform in thickness over theentire surface.

Plating Problems

Two serious problems are directlyattributed to plating – threadassembly and hydrogenembrittlement.

Thread Fit

The addition of a plating to itssurface increases the size of thefasteners. When the platingthickness exceeds certain limits –generally one-fourth of thespecified allowance for the class ofthread fit – there is a distinctpossibility the internally andexternally threaded parts will notassemble. When interferencebetween mating threads is likely,some accommodation must bemade prior to plating.Recommended practices foradjusting thread fits of platedfasteners are discussed inAS 1897-1976.

HydrogenEmbrittlement

High strength, high hardnesscarbon steel fasteners have asusceptibility to embrittlement,which evidences itself in variousmechanisms. Plated and coatedfasteners, especially those that areelectroplated, are vulnerable to theone known as hydrogenembrittlement.

Hydrogen embrittlement causesfastener failures, the actual fractureof the fastener into two separatepieces. The failure occurs in service(ie after the fastener has beeninstalled and tightened in itsapplication), it usually happenswithin hours, it's sudden, there'sno advance warning or visibleindication of imminence.

To neutralise the threat ofhydrogen embrittlement, fastenersare thermally baked as early aspossible after plating. Time delaysseriously jeopardise theeffectiveness and benefits of thebaking. The purpose of the baking– generally at 190°-210° for 3 to 24hours dependent on plating typeand thickness – is to drive out thehydrogen by bleeding it throughthe plating. Baking is always doneprior to chromating or applicationof any other supplementarycoating.

In broad terms, fasteners withhardnesses less than Rockwell C32have a low risk of embrittlement.Those with higher hardnessesshould always be suspect.

Because mechanical plating is non-electrolytic, the hydrogenembrittlement thread is virtually

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F A S T E N E R SCorrosive Protective Coatings

eliminated. In fact, parts withhardnesses up to Rockwell C55,mechanically plated without postbaking, have performedsatisfactorily without evidence ofembrittlement.

Hot-dip galvanised fasteners arerarely subject to hydrogenembrittlement. The primary reasonis that engineering standardsstrongly discourage the hot-dipgalvanising of fasteners withhardnesses higher than RockwellC35 – ie fasteners stronger thanAS 1110 – 8.8, AS 1252 – 8.8 andAS 2465 – Grade 5. The reason isthat galvanised fasteners of higherstrengths have a susceptibility toanother embrittlement mechanismknown as stress corrosion or stresscorrosion cracking.

Chemical ConversionCoatings

Chemical conversion coatings areadherent films chemically formedon a metal's surface whenimmersed in a bath of appropriatesolution. Chemical conversioncoatings popularly specified forfasteners are chromate treatmentson electroplated parts (mentionedearlier) and zinc and manganesephosphate coatings.

Zinc phosphate coatings, ormanganese phosphate often usedas a permitted alternative, areextensively specified for fasteners,particularly those intended for usein automotive application. Thephosphate base provides anexcellent substrate for painting andfor retention of oils, waxes orother organic lubricating materials.

Most zinc phosphated fastenersare additionally oiled to enhancecorrosion resistance and to helpcontrol torque-tensionrelationships. Dry zinc phosphateis often used as a base for non-metallic locking elements onexternally threaded fasteners.

The corrosion resistance of zincphosphated and oiled fasteners isreasonably good in non-aggressive atmospheres. Significantimprovements are possiblethrough secondary treatments,such as painting.

Although phosphate-coated highstrength fasteners are not immuneto hydrogen embrittlement,susceptibility and frequency ofoccurrence are less than similarfasteners which have beenelectroplated. Unlike depositedplating, phosphate coatings do notsignificantly increase fastener size.Tolerance 6g/6H (Class 2A/2B)screw thread fits are usuallyadequate to permit assembly.Rarely is it necessary to makeadjustments in thread size limitsprior to coating.

One of the more importantconsiderations when evaluatingthe possible use of phosphatecoated fastener is cost. Phosphateand oiled coatings are lessexpensive than zinc electroplatingwith chromate treatment.However, the packaging andhandling of phosphate and oiledfasteners has a degree of sensitivitybecause the oil may be removedby absorption into the packingmaterials.

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Corrosive Protective Coatings

Fastener CoatingSelection Chart

Table No 61 is condensed fromBlacks Bulletin No. 6-69, wherematerials other than steel areincluded (eg stainless steel, brass,

aluminium). It givesrecommendations as to thefinishes on steel bolts which areconsidered satisfactory – from thecorrosion viewpoint – for thejoining of metals which couldcause "galvanic" effects.

Australian Standards associated with corrosion protective coatings are:

Metric

AS 1110-1984 ISO Metric HexagonPrecision Bolts and Screws.

AS 1111-1980 ISO Metric HexagonCommercial Bolts and Screws.

AS 1112-1980 ISO Metric HexagonNuts.

AS 1214-1983 Hot-dip GalvanisedCoatings on Threaded Fasteners (ISOMetric).

AS 1252-1983 High Strength SteelBolts with associated Nuts andWashers for Structural Engineering(ISO metric).

AS 1390-1974 Metric Cup Head Bolts.

AS 1559-1986 Fasteners – Bolts, Nutsand Washers for Tower Construction.

AS 1791-1986 Chromate ConversionCoatings Zinc and Cadmium.

AS 1897-1976 Electroplated Coatingson Threaded Components (ISOMetric).

Inch

AS B108-1952 Black Cup andCountersunk Bolts, Nuts and Washers.

AS 2465-1981 Unified Hexagon Bolts,Screws and Nuts (UNC and UNFthreads).

AS B193-1970 Hot-dip GalvanisedCoatings on Fasteners (BSW andUNC threads).

AS K132.2-1973 ElectroplatedCoatings on Threaded Components(Zinc on Steel).

AS 1627.6-1977 Phosphate Treatmentof Iron and Steel Surfaces.

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F A S T E N E R SCorrosive Protective Coatings

Table 61

Metal Joined Bolt Coating

Gal- Zinc Cad- Chrom- Lead Black or Austen-vanised Plated mium ium /Tin Bright itic

Plated Plated2 Plated S/Steel

Steel, Cast Iron S S S S S R S

Zinc Coated Steel R S1 S1 S S U S

Tin Coated Steel U U U S U U R

Chromium Plated Steel U U U R U U R

Stainless Steel U U U S U U R

Aluminium S3 S3 R S S U R

Copper, Brass U U U U U U S

Nickel, Monel U U U S U U S

Lead U U U S R R

Key to performance: R = Recommended

S = Satisfactory

U = UnsuitableNOTES

1. Protection of the small area of the fastener depends on amount of zincavailable on the surrounding galvanised surface.

2. “Chromium plated” - including the trade term “chrome plated” - means platedwith a thin layer of chromium over a more substantial layer of nickel (andperhaps copper).

3. Aluminium is the protected member of aluminium-zinc combinations, causingaccelerated corrosion of the zinc. Since wastage of the zinc coating willeventually lead to exposure of the basis steel of the fastener, and then thisbare steel could accelerate corrosion of the aluminium and also causestaining - the greater the available amount of zinc the better. Thus, in theabsence of painting, the more heavily coated hot dipped galvanisedfastening is a better choice than its zinc plated counterpart.

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Tapping Drill Tables

The tapping drills given in thefollowing pages include millimetresizes for the convenience of thosewho are working in or intend towork predominantly in metricunits.

Drills have been selected fromstandard sizes which, when usedwith reasonable care, will produceholes within the minor diameterlimits shown.

From those drills the larger sizesare recommended to facilitate easeof tapping.

As a guide to relative clearances,index figures adjacent to the drillsize show the difference betweenthe nominal drill and minimumminor diameters.

Table 62 ISO Metric Coarse Pitch Series

Thread Size Minor Diameter Tapping Drill Sizesand Pitch of nut thread (A) for Commercial Tapping

Maximum Minimum Recommended Alternatives

mm mm mm mm Inch mm

M1.6 x 0.35 1.321 1.221 1.303 3/640 1.251

M2 x 0.4 1.679 1.567 1.654 1/161 1.601

M2.5 x 0.45 2.138 2.013 2.103 No. 469 2.051

M3 x 0.5 2.599 2.459 2.553 No. 410 2.501

M4 x 0.7 3.422 3.242 3.406 No. 301 3.302

M5 x 0.8 4.334 4.134 4.306 No. 193 4.202

M6 x 1.00 5.133 4.917 5.107 No. 92 5.003

M8 x 1.25 6.912 6.647 6.9010 17/644 6.806

M10 x 1.5 8.676 8.376 8.609 Q2 8.505

M12 x 1.75 10.441 10.105 10.4011 13/328 10.204

M16 x 2.00 14.210 13.835 14.006 35/642 –

M20 x 2.5 17.744 17.294 17.508 11/167 –

M24 x 3.0 21.252 20.752 21.0010 53/6411 –

M30 x 3.5 26.771 26.211 26.5011 13/6415 –

M36 x 4.0 32.270 31.670 32.0013 117/6419 –(A) From AS 1275 for Class 6H

The small index figures show the theoretical clearance in thousandths of aninch above the minimum minor diameter of the nut thread.

Letter and wire gauge drills are obsolescent and are being replaced by metricsizes.

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Tapping Drill Tables F A S T E N E R S

Table 63 British Standard Whitworth – BSW

Thread Size Minor Diameter Tapping Drill Sizesand Threads of nut thread (A) for Commercial Tapping

per inch Maximum Minimum Recommended Alternatives

Inch Inch Inch mm Inch

1/8 – 40 0.1020 0.0930 397 2.557 405

3/16 – 24 0.1474 0.1341 2710 3.7012 286

1/4 – 20 0.2030 0.1860 910 5.0011 107 123

5/16 – 18 0.2594 0.2413 1/49 6.4011 D5 C1

3/8 – 16 0.3145 0.2950 N7 7.708 19/642 S2

7/16 – 14 0.3674 0.3461 T12 9.1012 Y11 X4

1/2 – 12 0.4169 0.3932 13/3213 10.4013

9/16 – 12 0.4794 0.4557 15/3213 12.007

5/8 – 11 0.5338 0.5086 17/3223 13.5023 33/647

3/4 – 10 0.6490 0.6220 41/6419 16.2517 5/83

7/8 – 9 0.7620 0.7328 3/417 19.0015 47/642

1 – 8 0.8720 0.8400 55/6419 22.0026 27/321

11/8 – 7 0.9776 0.9420 31/3217 24.5022 61/6411

11/4 – 7 1.1026 1.0670 13/3227 27.5016 15/6411

11/2 – 6 1.3269 1.2866 15/1626 33.0012 119/6411

13/4 – 5 1.5408 1.4938 117/3237 38.5022 133/6420

2 – 4.5 1.7668 1.7154 13/435 44.5037 147/6420

(A) From AS B47 – normal and medium classes.

The small index figures show the theoretical clearance in thousandths of an inchabove the minimum minor diameter of the nut thread.

Letter and wire gauge drills are obsolescent and are being replaced by metricsizes.

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Thread Screw PitchesF A S T E N E R S

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Table 64

Inch Series

Dia. in Threads per inchinches BSW BSF UNC UNF

No. 8 – – 32 36

No. 10 – – 24 323/16 24 32 – –1/4 20 26 20 285/16 18 22 18 243/8 16 20 16 247/16 14 18 14 201/2 12 16 13 209/16 12 16 12 185/8 11 14 11 183/4 10 12 10 167/8 9 11 9 14

1 8 10 8 12

11/8 7 9 7 12

11/4 7 9 7 12

13/8 6 8 6 12

11/2 6 8 6 12

15/8 5 8 – –

13/4 5 7 5 –

2 4.5 7 4.5 –

21/4 4 6 4.5 –

21/2 4 6 4 –

23/4 3.5 6 4 –

3 3.5 5 4 –

ISO Metric PreferredCoarse Pitch Series

Dia in mm Pitch in mm

1.6 0.35

2 0.4

2.5 0.45

3 0.5

4 0.7

5 0.8

6 1

8 1.25

10 1.5

12 1.75

16 2

20 2.5

24 3

30 3.5

36 4

42 4.5

48 5

56 5.5

64 6

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Hardness Conversion Table F A S T E N E R S

Table 65

Rockwell SuperficialBrinell Hardness No.

Rockwell Rockwell Hardness Rockwell Rockwell Superficial BraleC-Scale B-Scale No. A-Scale D-Scale Penetrator

Vickers 150kg 100kg 3000kg Tensile Strength Shore 60kg 100kgHardness Load Load Load (Approximate) Sclero Load Load 15-N 30-N 45-N

Brale 11/16" dia 10mm scope Brale Brale Scale Scale ScalePene- Ball Ball Hardness Pene- Pene- 15kg 30kg 45kg-trator No. -trator -trator Load Load Load

HV HRC HRB HB lbf/in2 tonf/in2 N/mm2 HRA HRD HR HR HRx 1000 15-N 30-N 45-N

940 68 – – – – – 97 85.6 76.9 93.2 84.4 75.4

900 67 – – – – – 95 85.0 76.1 92.9 83.6 74.2

865 66 – – – – – 92 84.5 75.4 92.5 82.8 73.3

832 65 – 739 – – – 91 83.9 74.5 92.2 81.9 72.0

800 64 – 722 – – – 88 83.4 73.8 91.8 81 .1 71 .0

772 63 – 705 – – – 87 82.8 73.0 91.4 60.1 69.9

746 62 – 688 – – – 85 82.3 72.2 91.1 79.3 68.8

720 61 – 670 – – – 83 81.8 71.5 90.7 78.4 67.7

697 60 – 654 – – – 81 81.2 70.0 90.2 77.5 66.6

674 59 – 634 – – – 80 80.7 69.9 89.8 86.8 65.5

653 58 – 615 – – – 78 80.1 69.2 89.3 75.7 64.3

633 57 – 595 – – – 76 79.6 68.5 88.7 74.8 63.2

613 56 – 577 – – – 75 79.0 67.7 88.3 73.9 62.0

595 55 – 560 301 134 2080 74 78.5 66.9 87.9 73.0 60.9

577 54 – 543 292 130 2010 72 78.0 66.1 87.4 72.0 59.8

560 53 – 525 283 126 1950 71 77.4 65.4 86.9 71.2 58.6

544 52 – 512 273 122 1880 69 76.8 64.6 86.4 70.2 57.4

528 51 – 496 264 118 1820 68 76.3 63.8 85.9 69.4 56.1

513 50 – 481 255 114 1760 67 75.9 63.1 84.4 68.5 55.0

498 49 – 469 246 110 1700 66 75.2 62.1 85.0 67.0 53.8

484 48 – 451 237 106 1630 64 74.7 61 .4 84.5 66.7 52.5

471 47 – 442 229 102 1580 63 74.1 60.8 83.9 65.8 51.4

458 46 – 432 222 99 1530 62 73.6 60.0 83.5 64.8 50.3

446 45 – 421 215 96 1480 60 63.1 57.2 83.0 64.0 49.0

434 44 – 409 208 93 1430 58 72.5 58.5 82.5 63.1 47.8

423 43 – 400 201 90 1390 57 72.0 57.6 82.0 62.2 46.7

412 42 – 390 194 86.5 1340 56 71.5 56.9 81.5 61.3 45.5

402 41 – 381 188 84 1300 55 70.9 46.2 80.9 60.4 44.3

392 40 – 371 181 81 1250 54 70.4 45.4 80.4 59.4 43.1

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Hardness Conversion TableF A S T E N E R S

Fasteners your guarantee of quality industrial fasteners

Table 65 continued

Rockwell SuperficialBrinell Hardness No.

Rockwell Rockwell Hardness Rockwell Rockwell Superficial BraleC-Scale B-Scale No. A-Scale D-Scale Penetrator

Vickers 150kg 100kg 3000kg Tensile Strength Shore 60kg 100kgHardness Load Load Load (Approximate) Sclero Load Load 15-N 30-N 45-N

Brale 11/16" dia 10mm scope Brale Brale Scale Scale ScalePene- Ball Ball Hardness Pene- Pene- 15kg 30kg 45kg-trator No. -trator -trator Load Load Load

HV HRC HRB HB lbf/in2 tonf/in2 N/mm2 HRA HRD HR HR HRx 1000 15-N 30-N 45-N

382 39 – 362 176 78.5 1210 52 69.7 54.6 79.0 58.6 41.9

372 38 – 353 171 76.5 1180 51 69.4 53.8 77.4 57.7 40.8

363 37 – 344 168 75 1160 50 68.9 53.1 68.8 56.8 39.6

354 36 (109.0) 336 162 72.5 1120 49 68.4 52.3 78.3 55.9 38.4

345 35 (108.5) 327 157 70 1080 48 67.7 51.5 77.7 55.0 37.2

336 34 (108.0) 319 153 68.5 1050 47 67.4 50.8 77.2 54.2 36.1

327 33 (1 07.5) 311 149 66.5 1030 46 66.8 50.0 66.6 53.3 34.9

318 32 (1 07.0) 301 145 64.5 1000 44 66.3 49.2 76.1 52.1 33.7

310 31 (1 06.0) 294 142 63.5 979 43 65.8 48.4 75.6 51.3 32.5

302 30 (105.5) 286 138 61 .5 951 42 65.3 47.7 75.0 40.4 31 .3

294 29 (1 04.5) 279 135 60.5 931 41 64.7 47.0 74.6 47.5 30.1

286 28 (104.0) 271 132 59 910 41 64.3 46.1 73.7 48.6 28.9

279 27 (103.0) 264 128 57 883 40 63.8 45.2 63.3 47.7 27.8

272 26 (102.5) 258 125 56 862 38 63.3 44.6 72.8 46.8 28.7

266 25 (101.5) 253 122 54.5 841 38 62.8 43.8 72.2 45.9 25.5

260 24 (101.0) 247 120 53.5 827 37 62.4 43.1 71.6 45.0 24.3

254 23 100.0 243 117 52 807 36 62.0 62.1 71.0 44.0 23.1

248 22 99.0 237 114 51 786 35 61.5 41.6 70.5 43.2 22.0

243 21 98.5 231 112 50 772 35 61.0 40.9 69.9 42.3 20.7

238 20 97.8 226 110 49 758 34 60.5 40.1 69.4 41.5 19.6

230 (18) 96.7 219 106 47.5 731 33 – – – – –

222 (16) 95.5 212 102 45.5 703 32 – – – – –

213 (14) 93.9 203 98 44 676 31 – – – – –

204 (12) 92.3 194 94 42 648 29 – – – – –

196 (10) 90.7 187 90 40 621 28

188 (8) 89.5 179 87 39 600 27

180 (6) 87.1 171 84 37.5 579 26

173 (4) 85.5 165 80 35.5 552 25

166 (2) 83.5 158 77 34.5 531 24

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Hardness Conversion Table F A S T E N E R S

Table 65 continued

Rockwell SuperficialBrinell Hardness No.

Rockwell Rockwell Hardness Rockwell Rockwell Superficial BraleC-Scale B-Scale No. A-Scale D-Scale Penetrator

Vickers 150kg 100kg 3000kg Tensile Strength Shore 60kg 100kgHardness Load Load Load (Approximate) Sclero Load Load 15-N 30-N 45-N

Brale 11/6" dia 10mm scope Brale Brale Scale Scale ScalePene- Ball Ball Hardness Pene- Pene- 15kg 30kg 45kg-trator No. -trator -trator Load Load Load

HV HRC HRB HB lbf/in2 tonf/in2 N/mm2 HRA HRD HR HR HRx 1000 15-N 30-N 45-N

160 (0) 81.7 152 75 33.5 517 24

150 – 78.7 143 71 31.5 490 22

140 – 75.0 133 66 29.5 455 21

130 – 71.2 124 62 27.5 427 20

120 – 66.7 114 57 25.5 393 –

110 – 62.3 105 – – – –

100 – 56.2 105 – – – –

95 – 52.0 90 – – – –

90 – 48.0 86 – – – –

85 – 41.0 81 – – – –

The values shown in black type areagreed SAE-ASM-ASTM values aspublished in ASTM. E-140 Table 2.Values in blue type are given in SAEtables but are not agreed values.Values in ( ) are beyond the normalrange and are for information only.

IMPORTANTAll conversions must be regarded asapproximate and applying only tosteels. Australian Standard B-161indicates the limitations of accuracy ofconversion. Tensile strengthconversions do not specifically applyto cold worked steels.

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The Torquing of Stainless SteelF A S T E N E R S

Fasteners your guarantee of quality industrial fasteners

Stainless steel threads arenotorious for galling or seizingduring tightening. For a successfulassembly, tightening should becarried out with a slow smoothaction. Impact wrenches or airpowered screw drivers are notrecommended. In addition an anti-seize compound must be appliedto the threads. A high qualitynickel anti-seize has been found tobe very effective.

Recommended torque values arecalculated figures based uponseveral factors including friction,bolt diameter and proof stress. Asthe use of anti-seize is going tovary the friction characteristics ofthe assembly, the actual torque

required will also vary.Consequently the torque valuesquoted can only be regarded as aguide and bench trials should beconducted first.

Standard engineering practicerequires fasteners to be tightenedto a point where the includedscrew tension is 65-70% of theproof load. Once the proof load isexceeded the bolt will start tostretch permanently. Therefore,during the bench trials the torquerequired to start permanentstretching of the bolt should benoted. Applying 70% of this torquefigure will be a safe installationtorque.

Tightening Torques for Stainless Steel (304 and316) Metric Bolts

Grade GradeA2-70 and A4-70 A2-80 and A4-80

Recommended Assembly Torque Recommended Assembly Torqueto include 70% Proof Load to include 70% Proof Load

Nominal Diameter (NM) (ft lbf) (NM) (ft lbf)

M5 4.5 3.3 6.5 4.8

M6 7.6 5.6 11.1 8.2

M8 18.4 13.6 26.7 19.6

M10 37.0 27.0 52.6 38.7

M12 64.0 47.0 91.5 67.3

M16 158.0 116.7 223.0 163.9

M20 309.0 227.7 435.0 319.8

A few times each year we receivecalls from fasteners suppliers whoare in conflict with their customerover the quality of stainless steelbolts and nuts. The customer’s

complaint is that duringinstallation the bolts are twistingoff and/or the bolt’s threads areseizing to the nut’s thread. Thefrustration of the supplier is that

How To Stop Thread Galling on StainlessFasteners

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Mechanical Properties of Stainless Steel

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F A S T E N E R S

all required inspections of thefasteners indicate they areacceptable, but the fact remainsthat they are not working.

This problem is called “threadgalling”. According to the IndustrialFastener Institute’s 6th EditionStandards Book (page B-28),

“Thread galling seems to be themost prevalent with fasteners madeof stainless steel, aluminium,titanium and other alloys whichself-generate an oxide surface filmfor corrosion protection. Duringfastener tightening, as pressurebuilds between the contacting andsliding, thread surfaces, protectiveoxides are broken, possibly wipedoff, and interface metal high pointsshear or lock together. Thiscumulative clogging-shearing-locking action causes increasingadhesion. In the extreme, gallingleads to seizing – the actual freezingtogether of threads. If tightening iscontinued, the fastener can betwisted off or its threads ripped out.”

Carpenter Technologies, thefastener industry’s largest supplierof stainless steel raw material,refers to this type of galling in theirtechnical guide as “cold welding”.Anyone who has seen a bolt andnut with this problem understandsthe graphic nature of thisdescription.

The IFI and CarpenterTechnologies give three suggestionsfor dealing with the problem ofthread galling in the use ofstainless steel fasteners:

• Slowing down the installationRPM speed will frequentlyreduce, or sometimes solvecompletely, the problem. As the

installation RPM increases theheat generated during tighteningincreases. As the heat increases,so does the tendency for theoccurrence of thread galling.

• Lubricating the internal and/orexternal threads frequentlyeliminates thread galling. Thesuggested lubricants shouldcontain substantial amounts ofmolybdenum disulfide (,oly),graphite, mica, or talc. Someproprietary, extreme pressure,waxes may also be effective. Youmust be aware of the end usefor the fasteners before settlingon a lubricant. Stainless steel isfrequently used in food relatedapplications which may makesome lubricants unacceptable.Lubricants can be applied at thepoint of assembly or pre-applied as a batch processsimilar to plating. Severalchemical companies offer anti-galling lubricants.

One such source, EMCorporation, suggests theirPermaslik® RAC product for useat the point of assembly. Theysuggest Everlube® 620C forbatch, pre-applying to stainlesssteel fasteners.

• Using different stainless alloygrades for the bolts and nutreduces galling. The key here isthe mating of materials havingdifferent hardnesses. If one ofthe components is 316 and theother is 304 they are less likelyto gall than if they are both ofthe same alloy grade. This isbecause the different alloyswork harden at different rates.

Another factor affecting thread

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Mechanical Properties of Stainless SteelF A S T E N E R S

Fasteners your guarantee of quality industrial fasteners

galling in stainless steel fastenerapplications is thread roughness.The rougher the thread flanks, thegreater the likelihood galling willoccur. In an application where thebolt is galling with the internalthread, the bolt is usuallypresumed to be at fault, because itis the breaking component.Generally, it is the internal threadthat is causing the problem insteadof the bolt. This is because mostbolt threads are smoother thanmost nut threads. Bolt threads aregenerally rolled, therefore, theirthread flanks are relatively smooth.Internal threads are always cut,producing rougher thread flanksthan those of the bolts they aremating with. The reason gallingproblems are inconsistent isprobably due largely to theinconsistencies in the tappingoperation. Rougher than normalinternal threads may be the resultof the use of dull taps or thetapping may have been done atinappropriately high RPM.

Fortunately, stainless steel bolt andnut galling problems do not occureveryday, but when they do itusually creates a customer crisis.Knowledge of why this occurs andhow to remedy it can save thesupplier much grief and manyheadaches.

Here are some questions thatshould be asked and thesuggestions that should be madeimmediately when you areconfronted with a customer’scomplaint about thread galling:

1. Are you using the same driver RPMyou have used in the past to install thesestainless fasteners?

If they say they are driving themfaster than in the past or if theysay this is a new application,suggested they immediately tryslowing the driver RPM and see ifthe problem goes away. In general,a stainless bolt of a given sizeshould be driven slower than asteel bolt of the same size.

2. Are the bolts and/or internal threadslubricated?

If they say “no”, suggest they trylubricating the bolts and/orinternal threads with one of thelubricants listed earlier in thearticle. If this eliminates the galling,you might want to batch lubricatethe remainder of the order toeliminate the extra work ofapplying lubricant at the point ofassembly.

In applications where galling is arepetitive problem, it is advisableto supply the fasteners with pre-applied lubrication to eliminatefuture problems.

3. Are you using the same grade ofstainless steel for the bolts and nuts?

If the answer is “yes”, you cansuggest changing one or the otherto a different grade.

Be sure the suggested grade meetstheir corrosion needs andchanging the material does notcause a procurement problem.

When thread galling occurs instainless steel bolt and nutapplications, do not panic. Try thesuggestions listed; one or acombination of these willprobably resolve the problemimmediately.

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Material Compatibility F A S T E N E R SM

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Established1989

Fastener Handbook

BLACKS FASTENERS LTD

AUCKLAND930c Great South RoadT: (09) 589 1036 F: (09) 589 1037

NELSONCorner Brilliant Place and Nayland RoadT: (03) 547 5102 F: (03) 547 0189

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CHRISTCHURCH521c Blenheim Road, SockburnT: (03) 348 0340 F: (03) 348 0346

INVERCARGILL156 Bond StreetT: (03) 214 4499 F: (03) 214 4489

Freephone: 0800 652 463 Freefax: 0800 652 464

www.blacksfasteners.co.nz