Nut Bolt & Washer

Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari Partha Pratim Adhikari

NUT, BOLT &

WASHER

Written by : Partha Pratim Adhikari


Notes on Nuts and Bolts

A screw thread is a helical groove on a shaft. When used for delivering power, it is called a drive screw. Drive screws aren't really all that efficient, as they loose a significant amount of power to friction. However, this friction can be put to use in the case of threaded fasteners. You might say that a drive screw is an inclined plane wrapped around a post, while a fastener is a wedge wrapped around a post.

Bolt Terms

A 1/2-13UNC-2A-3 bolt, with a 2" thread and a 1" shank.


As nuts and bolts are not perfectly rigid, but stretch slightly under load, the distribution of stress on the threads is not uniform. In fact, on a theoretically infinitely long bolt, the first thread takes a third of the load, the first three threads take three-quarters of the load, and the first six threads take essentially the whole load. Beyond the first six threads, the remaining threads are under essentially no load at all. Therefore, a nut or bolt with six threads acts very much like an infinitely long nut or bolt (and it's a lot cheaper).

Stress on bolt threads. Note how the majority of the stress is on the first thread to the left.

There is little point in having more than six threads in anything. Nuts with National Coarse threads typically have 5 threads in them, whereas nuts with National Fine threads have about 8 threads. Nuts are usually stronger than the bolts they are on, which is to say that the bolt will usually break before the nut strips. It is often said that two threads must be exposed above a nut. The reason for this is that the first two threads of a bolt are often poorly formed, and may not engage the nut properly. If they're not doing their share, the other threads in the nut will be overloaded, and the nut may strip.

Thread

%

%Sum

1 34% 34% 2 23% 55% 3 16% 71% 4 11% 82% 5 9% 91% 6 7% 98%


Thread Terms

Metric and American threads both conform to the same profile, a series of equilateral triangles with the crests chopped off and the roots rounded.

External Standard Thread Profile The depth of the threads is 54.127% of the distance between threads, and the radius of the rounded root is 14.434% of the distance between threads. Another way of looking at it would be to say that 1/8 of the height of each equilateral triangle is chopped off the top, and 1/4 of the height off the bottom, leaving only 5/8 of the height available. (The height of an equilateral triangle is equal to the width times half of the square root of three; 5/8 of this is 0.54127.)


The root diameter of the thread is the nominal diameter minus 108.3% of the pitch of the thread. This means that fine threads have larger root diameters than coarse threads, and thus larger tap drill sizes. For threading using a tap or die, most threads are not cut to full depth, but to 75% or so. The resulting threads are not quite as strong, but full depth threading is very hard on the tap or die. Threading on a lathe presents no difficulty cutting to full depth.

Thread Specifications

Thread specifications are written thus: 1/2-13UNC-2

which means: a. bolt diameter b. threads per inch

c. thread type d. fit class

There are four Fit Classes, ranging from falling-off-loose to scientific-instrument-tight.

Class 1 = Loose Class 2 = Free Class 3 = Medium Class 4 = Close The class is followed by an A for external (screw) threads and a B for internal (nut) threads. Most are class 2. 3 is for precision assembly, and 4 is used for things like lathe lead screws and measuring instruments. In November 1948, NATO issued a new standard for threads, the Unified National system. American bolts had flat-bottomed groves between threads, which interfered with British round-topped threads. Likewise, British bolts wouldn't fit American nuts. The Unified system uses a round-bottom grove to fit the British threads, and a flat-topped thread to fit the American threads, so it not only fit itself, but both existing systems.


American/United National Threads

Size

Diameter

TPI

Coarse

TPI Fine

Root Dia.

Coarse

Hex

Head Size

SAE

Washer ID

SAE

Washer OD

SAE Washer

Thickness

#0 0.0600 - 80 0.0447

#1 0.0730 64 72 0.0560

#2 0.0860 56 64 0.0668 3/32" 1/4" 1/32"

#3 0.0990 48 56 0.0771

#4 0.1120 40 48 0.0813 1/8" 5/16" 1/32"

#5 0.1250 40 44 0.0971

#6 0.1380 32 40 0.1073 5/32" 3/8" 3/64"

#8 0.1640 32 36 0.1299 3/16" 7/16" 3/64"

#10 0.1900 24 32 0.1570 7/32" 1/2" 1/16"

#12 0.2160 24 28 0.1722 1/4" 9/16" 1/16"

1/4" 0.2500 20 28 0.1850 3/8" 9/32" 5/8" 1/16"

5/16" 0.3125 18 24 0.2400 1/2" 11/32" 11/16" 1/16"

3/8" 0.3750 16 24 0.2940 9/16" 13/32" 13/16" 1/16"

7/16" 0.4375 14 20 0.3440 5/8" 15/32" 15/16" 1/16"

1/2" 0.5000 13 20 0.4000 3/4" 17/32" 1-1/16" 3/32"

9/16" 0.5625 12 18 0.4540 7/8" 19/32" 1-3/16" 3/32"

5/8" 0.6250 11 18 0.5070 15/16" 21/32" 1-5/16" 3/32"

3/4" 0.7500 10 16 0.6200 1-1/8" 13/16" 1-1/2" 1/8"

7/8" 0.8750 9 14 0.7310 15/16" 15/16" 1-3/4" 1/8"

1" 1.0000 8 12 0.8370 1-1/2" 1-1/16" 1-3/4" 1/8"

A much more complete table is available here.


Metric Threads

Diameter

Coarse Pitch mm

Fine Pitch mm

Root Dia. Coarse

mm

Hex Head Size mm

ISO Washer ID

mm

ISO Washer OD mm

ISO Washer Thickness

mm 1.1 0.25 0.8294

1.2 0.25 0.9294

1.4 0.30 1.075

1.6 0.35 1.221 3.2

1.8 0.35 1.421

2 0.40 1.567 4

2.2 0.45 1.713

2.5 0.45 2.013 5

3 0.50 2.459 5.5 3.4 7.0 0.6

3.5 0.60 2.850

4 0.70 0.50 3.242 7 4.5 9.0 0.9

4.5 0.75 0.50 3.688

5 0.80 0.50 4.134 8 5.5 10 11

5.5 0.50

6 1.00 0.50 4.917 10 6.7 12.5 1.8

7 1.00 0.75 5.917

8 1.25 0.75 6.647 13 8.7 17 1.8

9 1.25 0.75 7.647

10 1.50 0.75 8.376 16 10.9 21 2.2

11 1.50 0.75 9.376

12 1.75 0.75 10.11 18 13.4 24 2.7

14 2.00 1.00 11.83 21

16 2.00 1.00 13.83 24 17.4 30 3.3

18 2.50 1.00 15.29

20 2.50 1.00 17.29 30 21.5 37.9 3.3


Metric threads use the same thread profile as SAE threads. The biggest difference is that the thread pitch (distance between consecutive threads) is given instead of threads per unit distance.

Bolt Strength The Society of Automotive Engineering has issued standard J429, which sets forth standards for both strength. The SAE grade of a bolt is marked on it's head in the form of short radial lines, the number of lines being two less than the SAE grade (i.e.. 3 lines for grade 5).

SAE Grade

Size Range

Strengh (psi)

1 1/4" to 1-1/2" 60,000

2 1/4" to 3/4" 74,000

2 7/8" to 1-1/2" 60,000

5 1/4" to 1" 120,000

5 1-1/8" to11/2" 105,000

7 1/4" to 1-1/2" 133,000

8 1/4" to 1-1/2" 150,000

ASTM standards are sometimes used as well; A325 bolts are the equivalent of SAE 5, and A490 bolts are the equivalent of SAE 8.


Preload

A very misunderstood part of bolting stuff together is preload, which is the tension placed on the bolt by the nut (as opposed to the load). A sufficiently high preload will protect the bolt from fatigue as the load changes, as the varying load will change the clamping force on the bolted components, rather than the tension on the bolt. (This is not strictly true, but for a tinkerer like me, it's adequate.) As a rule of thumb, the preload should exceed the maximum load by 15% or so. In order for this to work, however, the joint must be stiffer than the bolt. For this reason, the shank of high-tech bolts are often necked down to the same diameter of the root of the thread. As long as it isn't thinner than the root of the thread, it isn't any weaker than the thread, and therefore doesn't effect overall bolt strength, but it is significantly less stiff than the original shank. There are two ways to measure preload on a bolt; a torque wrench, and by measuring the angle the nut has turned. Of the two, the latter is more accurate, as friction plays a significant - and more importantly, indeterminate - role when using a torque wrench.

Torque = K × preload × diameter

K, the so-called Nut Factor, usually varies between 0.3 and 0.1, and is very sensitive to a number of factors, ranging from temperature to thread condition, even to how fast the bolt is tightened. Measuring the angle the nut has turned is simply measuring how much the bolt is stretching, equal to the pitch (distance between threads) times the number of turns. Using this requires that the components being bolted don't compress much (or compress a known amount), and that the "spring rate" of the bolt be known.


Turns = preload ÷ (spring rate × pitch)

For example, if the "spring rate" of a 1/2-13 bolt is 50,000 pounds per inch (note that I made that up, and that most bolts will yield long before stretching an inch), and you need 500 pounds of preload, you'll need to stretch the bolt 500 ÷ 50000 = 0.01 inch. At 13 threads per inch (0.0769 inches per thread), this would equate to 0.13 turns, or about 45° past snug. If more than one bolt is used in a joint, and those bolts are closer together than about four diameters, the preload on one bolt will effect the preload on the other bolts by compressing the joint. This effect is called "crosstalk", and then all bets are off. Joints that are significantly less stiff than the bolts, such as joints involving gaskets, suffer much worse from crosstalk. The best way to control crosstalk is to use a carefully thought out tightening sequence (usually a spiral starting at the center, or for circular patterns, alternating bolts), and to tighten the bolts in small steps. Even so, it's a crap shoot.

All countries in the world except USA, Liberia, and Myanmar use millimeters (mm). USA citizens: Conversion factor is 25.400000 mm/inch. Areas herein are accurate to five significant digits using exact converted USA diameters and pitches (not rounded USA diameters and pitches listed herein). M and MJ are metric thread profiles. Size designations not beginning with "M" in Table 1 are UN and UNJ thread profiles (non-metric). Blank values in Table 1 mean nonexistent fastener size. Dark shaded values mean typically never used and typically unavailable fastener size. M and MJ are metric thread profiles. Size designations not beginning with "M" in Table 1 are UN and UNJ thread Profiles (non-metric), no longer used anywhere in the world except in a few behind-the-times organizations in USA. You can look up each value in Table 1, above, or you can use the Table 2 formulas to calculate the values yourself. In the following table, Dn is nominal shank diameter (fastener size) from Table 1. Pitch p is fastener longitudinal length per thread. Note that p = 1 / n, where n = threads per unit length. Le is thread engagement length.


Standard Metric and USA Bolt Shank Dimensions ( All dimensions in units of mm or mm square unless otherwise specified. )

Coarse Pitch Threads Fine Pitch Threads

Size

Desig- nation

Nomial (Major) Diam-

eter

Nomial Shank Area

Threads

per inch

Pitch (mm per

thread),

Pitch Dia-

meter

Minor Dia-

meter Area

M,

UNC, UNRC Tensile Stress Area

MJ,

UNJC Tensile Stress Area

Threads

per inch

Pitch (mm per

thread)

Pitch Dia-

meter

Minor Dia-

meter Area

M,

UNF, UNRF Tensile Stress Area

MJ,

UNJF Tensile Stress Area

( D n ) ( A n ) ( n ) ( p ) ( d p ) ( A s ) ( A ts) ( A ts ) ( n ) ( p ) ( d p ) ( A s ) ( A ts ) ( A ts ) 0 1.5240 1.8241 80 0.31750 1.3178 0.9704 1.1588 1.3639

M1.6 1.6000 2.0106 0.35000 1.3727 1.0762 1.2700 1.4799

1 1.8542 2.7002 64 0.39688 1.5964 1.4074 1.6915 2.0016 72 0.35278 1.6251 1.5304 1.7920 2.0741

M2 2.0000 3.1416 0.40000 1.7402 1.7890 2.0732 2.3784

2 2.1844 3.7476 56 0.45357 1.8898 1.9986 2.3847 2.8049 64 0.39688 1.9266 2.1874 2.5383 2.9153

M2.5 2.5000 4.9087 0.45000 2.2077 2.9801 3.3908 3.8280

3 2.5146 4.9662 48 0.52917 2.1709 2.6222 3.1386 3.7014 56 0.45357 2.2200 2.9116 3.3741 3.8707

4 2.8448 6.3561 40 0.63500 2.4324 3.2045 3.8922 4.6467 48 0.52917 2.5011 3.6555 4.2611 4.9130

M3 3.0000 7.0686 0.50000 2.6752 4.4734 5.0308 5.6210

M3.5 3.5000 9.6211 0.60000 3.1103 5.9997 6.7752 7.5979

6 3.5052 9.6497 32 0.79375 2.9896 4.8075 5.8615 7.0199 40 0.63500 3.0928 5.6424 6.5440 7.5124

M4 4.0000 12.566 0.70000 3.5453 7.7496 8.7787 9.8720

8 4.1656 13.628 32 0.79375 3.6500 7.7166 9.0379 10.464 36 0.70556 3.7073 8.2910 9.5016 10.795

10 4.8260 18.292 24 1.0583 4.1386 9.3546 11.311 13.452 32 0.79375 4.3104 11.311 12.899 14.593

M5 5.0000 19.635 0.8000 4.4804 12.683 14.183 15.766

12 5.4864 23.641 24 1.0583 4.7990 13.277 15.590 18.088 28 0.90714 4.8972 14.576 16.638 18.836


M6 6.0000 28.274 1.0000 5.3505 17.894 20.123 22.484

0.2500 6.3500 31.669 20 1.2700 5.5251 17.351 20.530 23.976 28 0.90714 5.7608 21.006 23.467 26.065

0.3125 7.9375 49.483 18 1.4111 7.0210 29.267 33.826 38.715 24 1.0583 7.2501 33.826 37.462 41.284

M8 8.0000 50.265 1.2500 7.1881 32.841 36.609 40.581 1.0000 7.3505 36.030 39.167 42.435

0.3750 9.5250 71.256 16 1.5875 8.4939 43.741 49.994 56.663 24 1.0583 8.8376 52.170 56.663 61.342

M10 10.000 78.540 1.5000 9.0257 52.292 57.990 63.981 1.2500 9.1881 56.297 61.199 66.304

0.4375 11.112 96.987 14 1.8143 9.9341 60.210 68.586 77.508 20 1.2700 10.288 70.327 76.591 83.123

M12 12.000 113.10 1.7500 10.863 76.247 84.267 92.687 1.2500 11.188 86.037 92.072 98.311

0.5000 12.700 126.68 13 1.9538 11.431 81.103 91.548 102.63 20 1.2700 11.875 95.903 103.20 110.76

M14 14.000 153.94 2.0000 12.701 104.71 115.44 126.70 1.5000 13.026 116.13 124.55 133.26

0.5625 14.288 160.33 12 2.1167 12.913 104.55 117.38 130.96 18 1.4111 13.371 121.82 130.96 140.42

0.6250 15.875 197.93 11 2.3091 14.375 130.20 145.81 162.30 18 1.4111 14.958 154.86 165.13 175.74

M16 16.000 201.06 2.0000 14.701 144.12 156.67 169.74 1.5000 15.026 157.47 167.25 177.32

0.7500 19.050 285.02 10 2.5400 17.400 194.84 215.78 237.79 16 1.5875 18.019 226.65 240.62 255.00

M20 20.000 314.16 2.5000 18.376 225.19 244.79 265.22 1.5000 19.026 259.00 271.50 284.30

M22* 22.000 380.13 2.5000 20.376 281.53 303.40 326.09 1.5000 21.026 319.20 333.06 347.21

0.8750 22.225 387.95 9 2.8222 20.392 270.51 297.89 326.59 14 1.8143 21.047 310.03 328.69 347.90

M24 24.000 452.39 3.0000 22.051 324.27 352.50 381.91 2.0000 22.701 364.61 384.42 404.74

1.0000 25.400 506.71 8 3.1750 23.338 355.51 390.80 427.77 12 2.1167 24.025 402.94 427.77 453.34

M27* 27.000 572.56 3.0000 25.051 427.09 459.41 492.90 2.0000 25.701 473.22 495.74 518.79

1.1250 28.575 641.30 7 3.6286 26.218 447.18 492.44 539.88 12 2.1167 27.200 523.82 552.08 581.08

M30 30.000 706.86 3.5000 27.727 518.99 560.59 603.79 2.0000 28.701 595.96 621.20 646.97

1.2500 31.750 791.73 7 3.6286 29.393 574.10 625.23 678.55 12 2.1167 30.375 660.54 692.22 724.65

M33 33.000 855.30 3.5000 30.727 647.19 693.55 2.0000 31.701 732.83 760.80 789.29

1.3750 34.925 957.99 6 4.2333 32.175 680.06 745.09 813.09 12 2.1167 33.550 813.09 848.20 884.06

M36 36.000 1017.9 4.0000 33.402 759.28 816.72 876.26 2.0000 34.701 883.85 914.53 945.74

1.5000 38.100 1140.1 6 4.2333 35.350 834.73 906.62 981.47 12 2.1167 36.725 981.47 1020.0 1059.3

M6 6.0000 28.274 1.0000 5.3505 17.894 20.123 22.484

* M22 x 2.5 and M27 x 3 for high strength structural steel fasteners only.


Bolt Shank Geometric Formulas

Fastener

Stress Analysis

Quantity

Description

Sym

- bol

Value (for various Thread Profiles)

Source

M UN, UNR MJ UNJ

Thread profile angle a 60° 60° 60° 60° ISO 68-1, 1998, Fig. 1, p. 2.

Minor diameter

Dm Dn – 1.226869 p Dn – 1.299038 p Same as M profile.

Same as UNR profile.

ISO 898-1, 1999, Sect. 8.2, p. 13; ASME B1.1, 1989, Sect. 8.3.1.f, p. 53.

Tensile stress diameter Dts Dn – 0.938194 p Dn – 0.974279 p dp ISO 898-1, 1999, Sect. 8.2, p. 13; MIL-HDBK-60, 1990, Sect. 110.1, p. 27.

Pitch diameter dp Dn – 0.75 p sin a ISO 724, 1993, p. 2.

Shear stress diameter, shank in shear plane

Ds Dn Shear stress diameter, shank in shear plane

Shear stress diameter, threads in shear plane

Ds Dts. Or you can conservatively use Dm. NASA TM-106943, 1995, p. 16.

Thread shear (stripping) area, sloppy thread

tolerances

Ath 0.333 p dp Le Barrett, Fastener Design Manual, NASA RP-1228, 1990, p. 21.

Thread shear area, both threads class 2 or 3 (ISO

class 6H/6g) thread tolerance

Ath 0.5 p dp Le FED-STD-H28/2B, 1991, Table II.B.1, p. 57, Eq. 7.

Thread engagement length. In general, according to Machine Design magazine, the minimum recommended length of engagement is 0.75 to 1 times the bolt major diameter for threading into steel and other materials of comparable hardness; and 1 to 1.5 times the bolt major diameter for threading into brass, cast iron, and aluminum. These lengths of engagement specified are for full threads engaged, not overall bolt length. Regarding partial threads in the chamfers on the ends of internal or external threads, FED-STD-H28/2B, 1991, Sect. 7.7.2, p. 61, specifies that approximately half the countersink or chamfer depth may be included in the length of engagement calculation.


Metric Bolt Strength

General Fasteners a. USA industry is now using metric fasteners extensively. The remainder of the world uses ISO metric fasteners almost exclusively, due to their superiority in proportions, fatigue strength, pitch, size and specification designations, and international availability. b. The Thomas Register lists hundreds of firms under Metric Fasteners, Metric Screws, and Metric Bolts. The Industrial Fasteners Institute (IFI) has guides for fastener types and producers. c. Metric fasteners for all aerospace applications are made readily and easily available at "rock" bottom price to all NASA and contractor employees via NASA GSFC Fastener Inventory. d. Metric fastener size designation. i. Metric fastener size designation nomenclature. As fully explained in ISO 965-1, Sect. 5, metric fastener size designations always begin with capital M or MJ followed by fastener nominal diameter and thread pitch, both in units of millimeters (mm), separated by the symbol "x", as follows. M10 x 1.5-6g-S means metric fastener thread profile M, fastener nominal size (nominal major diameter) 10 mm, thread pitch 1.5 mm, external thread tolerance class 6g, and thread engagement length group S ("short"). If referring to internal thread tolerance, "g" would be capitalized. A fit between threaded parts is indicated by internal thread tolerance class followed by external thread tolerance class separated by a slash; e.g., M10 x 1.5-6H/6g. ii. Default metric fastener thread pitch and engagement length. If metric thread pitch designation (e.g., " x 1.5") is omitted, it specifies coarse pitch threads. For example, M10 or M10-6g, by default, specifies M10 x 1.5.


The standard metric fastener thread series for general purpose threaded components is the M thread profile and the coarse pitch thread series. If thread engagement length group designation (e.g., "-S") is omitted, it specifies thread engagement length group N meaning "normal." iii. Default metric fastener thread tolerance class. If thread tolerance class designation (e.g., "-6g") is omitted (e.g., M10 x 1.5), it specifies "medium" thread tolerance, which is 6H/6g. The 6H/6g fit is the standard ISO tolerance class for general use. iv. Equivalent imperial thread tolerance classes. Imperial internal and external thread tolerance class 2B/2A is essentially equivalent to ISO thread tolerance class and fit 6H/6g. Imperial tolerance class 3A is approximately equivalent to ISO tolerance class 4g6g, though class fit 3B/3A is approximately equivalent to ISO class fit 4H5H/4h6h. For full details, see ISO 965-1, Sects. 5.2, 7, and 12. v. Metric fastener thread profile compatibility. Metric fastener thread profile M is the normal, commercially- available thread profile. Thread profile MJ designates the external thread has an increased root radius (shallower root relative to external M thread profile), thereby having higher fatigue strength (due to reduced stress concentrations), but requires the truncated crest height of the MJ internal thread to prevent interference at the external MJ thread root (just as the UNJ external thread profile requires the UNJ internal thread). However, M external threads are compatible with M and MJ internal threads (just as UN and UNR external threads are compatible with UN and UNJ internal threads). e. ISO metric fastener material strength property classes (grades). As given in ISO 898-1, ISO metric fastener material property classes (grades) should be used. For example, fastener material ISO property class 5.8 means nominal (minimum) tensile ultimate strength 500 MPa and nominal (minimum) tensile yield strength 0.8 times tensile ultimate strength or 0.8(500) = 400 MPa. (In a few cases, the actual tensile ultimate strength may be approximately 20 MPa higher than ominal tensile ultimate strength indicated via the nominal property class code. Consult Table 10, below, for exact values.) Many anchor bolts (L, J, and U bolts, and threaded rod) are made from


low carbon steel grades, such as ISO classes 4.6, 4.8, and 5.8. f. Preferred diameters. Preferred nominal diameters for bolts and threaded rod are as listed below. The fourth series listed below should be limited to unusual requirements when none of the preceding series can be used. Reference individual standards prior to specification. Sizes M5 to M45 are commonly used in construction. First choice: M2 2.5 3 4 5 6 8 10 12 16 20 24 30 36 42 Second choice: M3.5 14 18 22 27 33 39 45 Third choice: M15 17 25 40 Avoid: M7 9 11 26 28 32 35 38 g. Bolt versus screw definition. The correct definition of bolt and screw is as follows. Bolts are headed fasteners having external threads that meet an exacting, uniform bolt thread specification (such as M, MJ, UN, UNR, and UNJ) such that they can accept a nontapered nut. Screws are headed, externally-threaded fasteners that do not meet the above definition of bolts. For full discussion of misdefinitions and corresponding confusion regarding these two words, see details. h. Handy conversion factors. Imperial conversion factors, verified accurate to the decimal places shown via multiple,independent, credible sources, are 25.4 mm/inch (exact), 4.4482216152605 N/lbf, 6.89475729318 MPa/ksi, 47.880259 Pa/psf, 112.98483 (N mm)/(in lbf), 157.08746 (N/m^3)/pcf, 16.0184634 (kg/m^3)/(lbm/ft^3), 27679.9047 (kg/m^3)/(lbm/in^3), 9.80665 (m/s^2)/gravity (exact). Rounding these conversion factors to a few less decimal places, we have 4.448222 N/lbf, 6.89476 MPa/ksi, 47.8803 Pa/psf, 113.0 (N mm)/(in lbf), 157.087 (N/m^3)/pcf, 16.01846 (kg/m^3)/(lbm/ft^3), 27679.9 (kg/m^3)/(lbm/in^3). i. Metric system (SI). The abbreviation for the metric system is SI, the International System of Units (from the French, Systeme International d'Unites). It evolved from the original French metric system and is currently being used virtually worldwide. Long the language universally used in science and among technically adept individuals,


SI has also become the dominant language of international commerce and trade. All new USA standards (ASTM, ANSI, SAE, IEEE, ASME, etc.) are now written in metric, as the lead engineers in these organizations recognize the importance of trying to get the USA on track with technically advanced countries, in an effort to regain lost USA competitiveness in a global economy, as there is essentially no global market for the archaic, oddball, incompatible product dimensions USA arbitrarily comes up with, while they forfeit industries and jobs to third- world countries who have no problem understanding something so simple and fulfilling the need efficiently. IEEE was intelligent enough to recognize this decades ago. Japan also was intelligent enough to recognize simple matters such as this long ago. This small country, defeated in WWII only 60 years ago, has since captured a large portion of the global economy due to their intelligent progress, and consequently has become a major global financier, while USA has become a world-class debtor to the tune of trillions due to inefficient business practices, low educational level, slackerism, and inability to solve or understand even simple problems such as metric conversion.

Fastener Data Tables 2 and 3 provide much of the data available for different metric fasteners. Table 2 comes verbatim from Ref. 1, including what appear to be a few typos, marked "[sic]," below. Table 3, on the other hand, has been verified accurate per ISO 898-1 and ASTM F 568M.


FASTENER DATA (Table No. 2)

Basic Product

Product Type and Head Style

Available

Size Range

For thread and dimension

details refer to:

For mechanical property

details refer to Table 3 or

Metric Bolts

Metric Bolts hex M5-M100

ASTM F568M ASTM F486M ASTM F738M

heavy hex M12-M36 ANSI/ASME B18.2.3.6M round head short square neck

(carriage) M8-M20 ANSI/ASME B18.5.2.1M

round head square neck (carriage) M5-M24 ANSI/ASME B18.5.2.2M bent M5 and larger IFI 528 [sic]

heavy hex structural M12-M36 ANSI/ASME B18.2.3.7M ASTM A325M ASTM A490M

hex transmission tower M16-M24 IFI 541 [sic] IFI 541 [sic]

Metric Screws

hex cap M5-M100 ANSI/ASME B18.2.3.1M

ASTM F568M ASTM F468M ASTM F738M

formed hex M5-M24 ANSI/ASME B18.2.3.2M

heavy hex M12-M36 ANSI/ASME B18.2.3.3M hex flange M5-M16 ANSI/ASME B18.2.3.4M

heavy hex flange M10-M20 ANSI/ASME B18.2.3.9M hex lag M5-M24 ANSI/ASME B18.2.3.8M

Metric Studs

double end M5-M100 IFI 528 [sic] ASTM F568M ASTM F468M ASTM F736M

continuous thread M5-M100

Metric Locking

Screws

prevailing torque, non-metallic insert M1.6-M36 see note 3 [sic] IFI 524 chemical coated M6-M20 see note 3 [sic] IFI 525

Metric Socket Screws

socket head cap M1.6-M48 ANSI/ASME B18.3.1M ASTM A574M ASTM F837M

socket head shoulder M6.5-M25 ANSI/ASME B18.3.3M ASTM F835M ASTM A574M ASTM F879M

socket button head cap M3-M16 ANSI/ASME B18.3.4M socket countersunk head cap M3-M20 ANSI/ASME B18.3.5M


Screws socket set M1.6-M24 ANSI/ASME B18.3.6M ANSI/ASME B18.3.6M ASTM F912M ASTM F880M

Metric Nuts

hex, style 1 M1.6-M36 ANSI/ASME B18.2.4.1M ASTM A563M ASTM F467M ASTM F836M ASTM A194M

hex, style 2 M3-M36 ANSI/ASME B18.2.4.2M

slotted hex M5-M36 ANSI/ASME B18.2.4.3M

hex flange M5-M20 ANSI/ASME B18.2.4.4M

hex jam M5-M36 ANSI/ASME B18.2.4.5M

heavy hex M12-M100 ANSI/ASME B18.2.4.6M

Metric Prevailing- Torque Nuts

hex, steel M3-M36 ANSI/ASME B18.16.3M ANSI/ASME B18.16.1M ANSI/ASME B18.16.2M hex flange, steel M6-M20

Notes for Table 3. When only the ISO property class number is shown in Table 3, below, the class is standard in both ISO 898-1 and ASTM documents. Properties specified in each are identical except for minor exceptions. Where differences exist, the ASTM F 568M values are given. To compute the tensile proof load, tensile yield strength, or tensile ultimate strength in kilonewtons (kN) for a bolt, screw, or stud, multiply the stress value (MPa) in Table 3 by the tensile stress area (mm^2) of the product's screw thread as given in Table 2 or Standard Metric Bolt Shank Dimensions, then divide this result by 1000. In general, identification markings are located on the top of the head and preferably are raised. Class 5.8 products are available in lengths 150 mm and less. Caution is advised when considering the use of property class 12.9 products. The capabilities of the fastener manufacturer, as well as the anticipated service environment, should be carefully considered. Some environments may cause stress corrosion cracking of nonplated, as well as electroplated, products.


MECHANICAL REQUIREMENTS FOR CARBON STEEL

EXTERNALLY-THREADED METRIC FASTENERS ( Table No. 3 )

Property

Class

Designation

Nominal

Size of

Product

Material and Treatment

Mechanical Requirements

Property

Class

Ident.

Marking

Proof

Load

Stress

, MPa

Tensile

Yield

Strength,

MPa, Min.

Tensile

Ultimate

Strength

MPa,

Min.

Prod. Hardness,

Rockwell

Surface

Max

Core

Min Max

4.6 M5-M100 low or medium carbon steel 225 240 400 -- B67 B95 4.6 4.8 M1.6-M16 low or medium carbon steel, fully or

partially annealed 310 340 420 -- B71 B95 4.8

5.8 M5-M24 low or medium carbon steel, cold worked

380 420 520 -- B82 B95 5.8

8.8 M16-M72 medium carbon steel, quenched and tempered

600 660 830 30N56 C23 C34 8.8 A325M Type 1 M16-M36 A325M 8S

8.8 M16-M36 low carbon boron steel, quenched and tempered

600 660 830 30N56 C23 C34 8.8 A325M Type 2 A325M 8S A325M Type 3 M16-M36 atmospheric corrosion resistant steel,

quenched and tempered 600 660 830 30N56 C23 C34 A325M8S3

9.8 M1.6-M16 medium carbon steel, quenched and tempered

650 720 900 30N58 C27 C36 9.8

9.8 M1.6-M16 low carbon boron steel, quenched and tempered

650 720 900 30N58 C27 C36 9.8

10.9 M5-M20 medium carbon steel, quenched and tempered

830 940 1040 30N59 C33 C39 10.9

10.9 M5-M100 medium carbon alloy steel, quenched and tempered

830 940 1040 30N59 C33 C39 10.9 A490M Type 1 M12-M36 A490M10S

10.9 M5-M36 low carbon boron steel, quenched and tempered

830 940 1040 30N59 C33 C39 10.9 A490M Type 2 M12-M36 A490M10S A490M Type 3 M12-M36 atmospheric corrosion resistant steel,

quenched and tempered 830 940 1040 30N59 C33 C39 A490M

10S3 12.9 M1.6-M100 alloy steel, quenched and tempered 970 1100 1220 30N63 C38 C44 12.9


Metric Standard Flat Washers Corresponds to standard JIS B 1256.

Name

Nominal

Size

Hole

Diameter

Outside

Diameter

Thickness

JWPCR01 6.00 6.60 12.50 1.60

JWPCR02 8.00 9.00 17.00 1.60

JWPCR03 10.00 11.00 21.00 2.00

JWPCR04 12.00 14.00 24.00 2.30

JWPCR05 16.00 18.00 30.00 3.20

JWPCR06 20.00 22.00 37.00 3.20

JWPCR07 24.00 26.00 44.00 4.50

JWPCR08 30.00 33.00 56.00 4.50

JWPCR09 36.00 39.00 66.00 6.00

JWPCR10 42.00 45.00 78.00 7.00

JWPCR11 48.00 52.00 92.00 8.00

JWPCR12 56.00 62.00 105.00 9.00

JWPCR13 64.00 70.00 115.00 9.00

JWPCR14 72.00 78.00 125.00 10.00

JWPCR15 80.00 86.00 140.00 12.00

JWPCR16 90.00 96.00 160.00 12.00

JWPCR17 10.00 107.00 175.00 14.00

JWPCR18 110.00 117.00 185.00 14.00

JWPCR19 125.00 132.00 220.00 16.00

JWPCR20 140.00 147.00 240.00 18.00


Metric Finished Flat Washers Corresponds to standard JIS B 1256.

Name

Nominal

Size

Hole

Diameter

Outside

Diameter

Thickness

JWPCF01 2.00 2.20 5.00 0.30

JWPCF02 2.50 2.70 6.50 0.50

JWPCF03 3.00 3.20 7.00 0.50

JWPCF04 4.00 4.30 9.00 0.80

JWPCF05 5.00 5.30 10.00 1.00

JWPCF06 6.00 6.40 12.50 1.60

JWPCF07 8.00 8.40 17.00 1.60

JWPCF08 10.00 10.50 21.00 2.00

JWPCF09 12.00 13.00 24.00 2.50

JWPCF10 16.00 17.00 30.00 3.00

JWPCF11 20.00 21.00 37.00 3.00

JWPCF12 24.00 25.00 44.00 4.00

JWPCF13 30.00 31.00 56.00 4.00

JWPCF14 36.00 37.00 66.00 5.00

JWPCF15 42.00 43.00 78.00 7.00

JWPCF16 48.00 50.00 92.00 8.00

JWPCF17 56.00 58.00 105.00 9.00

JWPCF18 64.00 66.00 115.00 9.00

JWPCF19 72.00 74.00 125.00 10.00

JWPCF20 80.00 82.00 140.00 10.00


Metric Small Flat Washers Corresponds to standard JIS B 1256.

Name

Nominal

Size

Hole

Diameter

Outside

Diameter

Thickness

JWSMC01 1.00 1.10 2.50 0.30

JWSMC02 1.20 1.30 2.80 0.30

JWSMC03 1.60 1.70 3.80 0.30

JWSMC04 2.00 2.20 4.30 0.30

JWSMC05 2.50 2.70 5.00 0.50

JWSMC06 3.00 3.20 6.00 0.50

JWSMC07 4.00 4.30 8.00 0.80

JWSMC08 5.00 5.30 10.00 1.00

JWSMC09 6.00 6.40 11.50 1.60

JWSMC10 8.00 8.40 15.50 1.60

JWSMC11 10.00 10.50 18.00 2.00

JWSMC12 12.00 13.00 21.00 2.50

JWSMC13 16.00 17.00 28.00 3.00

JWSMC14 20.00 21.00 34.00 3.00

JWSMC15 24.00 25.00 39.00 4.00

JWSMC16 30.00 31.00 50.00 4.00

JWSMC17 36.00 37.00 60.00 5.00

Documents

Nut Bolt & Washer