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है”ह”ह

IS 12186 (1987): Tolerances for ISO Metric trapezoidalscrew threads for lead and feed screw assemblies [PGD 20:Engineering Standards]

UD C 621’753.1 : 621’882’082’4 IS: 12186 - 1987

lndia~ Standard

TOL,ERANCES FOR

ISO ~VIETRIC TRAPEZOIDAL SCREW THREADS FOR

LEAD AND FEED SCREW ASSEMBLIES

I. Scope - Specifies tolerances for IS0 metric trapezoidal screw threads for machine tool lead 2nd feed screws and nuts.

1.1 Data relating to ‘measurement over rollers’ for IS0 metric trapezoidal screw threads for lead 2nd feed screws is given in Appendix A.

2. Basic and Design Profiles - Shall be as specified in IS: 7008 ( Part 1 )-I973 ‘IS0 metric irapezoidal screw threads: Part 1 Basic and design profiles’.

3. Pitch-Diameter Combinations - The recommended pitch-diameter combinations are given n Table 1.

1. Designation

1.1 Single-start IS0 metric trapezoidal screw threads conforming to this standard shall be desig- iated by the letters ‘Tr’ followed by values of nominal diameter and the pitch expressed in nillimetres and separated by the sign ‘X’.

Example:

Tr 40 x 8

I.2 Multi-start IS0 metric trapezoidal screw threads conforming to this standard shall be designat- ed by the letters ‘Tr’ followed by the values of the nominal diameter and lead for the multi-start threads, separated by sign ‘X’, and, in brackets the letter ‘P’ and the value of the pitch (distance aetween two neighbouring ridges ), all expressed in millimetres.

Example:

Tr 40 x 10 ( P 5 )

( Number of starts = E== F defines a screw thread of 40 diameter with 2 starts ).

6.3 To designate left hand IS0 metric trapezoidal screYv threads, the letters ‘LH’ shall be added to the thread designation:

Example:

Tr40 xlO(P5)LH

5. Classification of Lead and Feed Screws - Lead and feed screws are classified into 4 classes 3f accuracy, in the decreasing order of precision. The class of accuracy is selected foi different machine tools, depending on the overall accuracy of the mechanism required for that particular machine tool. Table 2 specifies the class of accuracy of lead and feed screws as applicable to various machine tools.

Adopted 14 August 1987 I

@ August 1988, BIS I

Gr 8

I

BUREAU OF INDIAN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

IS: 12186 - 1987

TABLE 1 RECOMMENDED PITCH-DIAMETER COMBINATIONS

( Clause 3 )

All dimensions in miliimetres. .

Nominal Diameter Pitch

-

I 4

4

-

-

- 4

--

4

--

--

_

_

--

- _

-_

-.

_

--

_-

w-

_ _

_-

_ -

-_

-_

__

_

--

-_

-_

_ .

-

4

4

_

-

--

_

_-

_ -

_-

_

_-

-

_-

.-

.-

. -

--

----l 6’

_____.

I -1 6” 1 I

.-

5

5

5

5

5

5 --

5*

5*

-,

5’

--

_

.

-_

- .

- .

- .

-

._

-_

_

-_

-

._

-

-

--- ___

--- - 6+

-

_.

_.

_-

_-

_-

__

.

-

- _

. _

- _

-

-

_ .

_

-.

_.

-

_ .

_

-_

- .

-

- _

_

. -

._

I -

a I IO --

--

--

I

.

.

--

--

--

--

--

--

3 Second Choice

First Choice

10

12

16

20

---

25

30

32 --

40

50

----

56

60

63

70

80 --

100

16 20

16

_

-.

_

.

_-

_-

-

_-

-

-

. -

_-

_-

_-

.-

.-

. _

-

-

20

20

20

12

--

12

12

12

12

12

12

2

2

-

- 2

.

-

. -

2

_-

_- 2

_-

_.

_-

_-

_ -

.

. -

-

.-

-

I

75

90 I

_

-

-_

- _

-.

-

- .

.

. _

.-

.-

-

.-

-

-

-

-

6

6

6

6

6

6

6

6+

6*

6*

6*

--

_

-

--

_ -

--

--

--

-

_ -

-.

--

-.

--

_ -

-I-

_-

_-

--

_ _

-

_-

_ -

_-

_-

-

3

3

14 3

ia

22

24

26

28

34

36

10

IO

--

10

IO

10 --

10

10

10

10

8

a

a

a --

a

a

a

a

44

46 _

.

_.

48

52

55

65

*Multi-start threads with 2 starts may be used.

2

IS : 12188 -1987

TABLE 2 CLASSIFICATION OF LEAD AND FEED SCREWS

( Clause 5 )

. Application

Thread grinding machines, master lead screws, jig boring machines, dividing machines working without correction equipment, NC machines, etc, and measur- ing instruments

Precision thread cutting machines, dividing equipment for precision machines, high precision lathes, relievinglathes, boring machines

Centre lathes and turret lathes, knee type milling machines, plano milling machines, thread milling machines

Machines which do not need special requirement for feed screws, for example, feed screws of slotting machines, screw for vices, etc

Note - It is recommended to use screw base system wherein the nut is suited to the screw,

6. Accuracy - The working accuracy of the lead screw depends on:

a) Dimensional accuracy of the major diameter, pitch diameter, minor diameter, lead ( pitch ) and the angle of the thread;

b) Geometrical accuracy of cylindricity and circularity on pitch diameter of the screw and radial runout of major diameter; and

c) Surface finish on the flanks of the threads for both screw and nut.

6.1 Dimensional Accuracy

6.1.1 Tolerances on major diameter, pitch diameter and the minor diameter of the screw, shall be as indicated in Tables 3, 4 and 5 respectively. Values of tolerance on the minor diameter of the screw are given for information only and are not normally inspected.

TABLE 3 TOLERANCE ON MAJOR DIAMETER OF SCREW

I Pitch, mm 2 3 4 5 6 8 10 12 16 20 ---------

Tolerance in pm for all classes of -180 -236 -300 -335 -375 -450 -530 -600 -710 -800 accuracy

Note - Upper limit is zero.

t$ :,t2189 T 1987

TABLE 4 TOLERANCE ON PITCH DIAMETER OF SCREW

( Clause 6.1.1 ) AlI dimensions in tIIi~hStrSS.

. Nominal Diameter Pitch Tolerance in pm for Class of Accuracy

Upper Limit Lower Limit -

From UP to For all 1 2 3 4 classes

2 -38 -156 -188 -228 -274

- IO

3 -48 -180 -212 -250 .-300

2 -38 -163 -198 -238 -288 -

3 -48 -188 -228 -272 -328

12 22 4 -60 -220 -260 -310 -375

5 -71 -251 -295 -351 -426

6 -80 -280 -315 -385 -460

2 -38 -180 -212 -250 -300

4 -60 -238 -280 -335 -400

5 -71 -261 -307 -371 -446

24 44 -~

6 -80 -292 -345 -415 -505

-- --

8 -85 -321 -385 -460 -560

--~~__

10 -96 -335 -400 -435 -585

p-

5 -71 -272 -315 -385 -460

6 -80 -307 -361 -431 -521

8 -85 -335 -400 -485 -585 ,

46 90

10 -96 -361 -431 -521 -626

-__

12 -115 -415 -490 -590 -715

20 -150 -446 -560 -670 -750 _.-

10 -96 -385 -446 -560 -670 ---

12 -115 -430 -515 -615 -745

100 16 -130 -485 -580 -690 -840

- 20 -150 -560 -630 -745 -900

IS:12188 -1987.

TABLE 5 TOLERANCE ON MINOR DIAMETER OF SCREW

( Clause 6.1 .l )

. All dimensions in millimetres.

Nominal Diameter Pitch I

Tolerance in pm for Class of Accuracy

I Lower Limit*

From up to 1 2 3 4

2 -150 -190 -236 -300

10 3 -160 -200 -250 -315

2 -160 -200 -250 -315 ~_

3 -180 -224 -280 -355

I I

I I I I

12 22 4 -200 - 250 -315 -400

5 -224

6 -250

2 -180

4 -224

24

46

100

-I -280

-320

-212

I -280

-355 -450

-400 -530

-261 -328

-355 -450 I I I I I I

44

90

-

5

6

a

10

5

6

a

10

12

20

10

12

16

20

-265 -335 I -425 I -530

-300

-320

-250

-280

-315

-335

-375

- 400

-355

-400

-450

-530

*Upper limit is zero for all classes of accuracy.

-300 I -3375 I -475

-375 -475 -600

-400 -460 -630 -

-320 -400 -530

-355 -450 -600

-400 -500 - 630 -

-425 -530 -670

-475 -600 -750

-500 -630 -300

-450 -585 -715 9

-500 -630 -800

-560 -710 -900

-600 -800 -1000

6.1.2 Tolerances on minor diameter, pitch diameter and the major diameter of the nut shall be as indicated in Tables 6, 7 and 8 respectively. Values of tolerance on major diameter are given only for information and are not normally inspected.

5

IS : 12186 - 19ti

TABLE 6 TOLERANCE ON MINOR DIAMETER OF THE NUT THREAD ( Clause 6.1.2 )

Pitch, mm

‘$=;;::e:: / +160 j +236 j +300 / +335 / +375 j $450 1 +530 / +600 / +710 / -1-300

Note - Lower limit is zero.

TABLE 7 TOLERANCE ON PITCH DIAMETER OF NUT THREAD / ( Clause 6.1.2 )

All dimensions in miilimetres.

Nominal Diameter Pitch Tolerance in pm for Class of Accuracy

Upper Limit*

From up to 1 and 2 3 4

2 +200 +250 +315 10

3 +228 $288 +355

2 +212 +265 f335

3 +236 +300 i-375

12 22 4 +265 +335 +425

5 +300 i-375 -I-475

6 +335 $412 +522

2 +228 +286 +355

4 +288 +355 +445

5 $315 f400 f500 24 44

6 +355 +450 +560

8 +400 +500 +630

10 $422 +525 +670

c 5 +355 $450 ’ +560

6 +400 +500 +600

6 +425 +530 $670 46 90

10 f450 $580 +710

12 +500 +630 +800

20 +560 f710 +900

10 +500 $630 $800

12 +530 f670 +850 100

/ 16 $560 +710 -!-go0

20 +630 +800 +1000

*Lower limit is zero for all classes.

6

IS :12186- 1987

TABLE 8 TOLERANCE ON MAJOR DIAMETER OF NUT THREAD ( Clause 6.1.2 )

. All dimensions in millimetres.

Nominal Diameter Pitch Tolerancein pm for Class of Accuracy

Upper Limit*

From up to 1 and 2 3 4

2 + 236 +300 + 365

10 --

3 + 250 +315 + 400

2 + 250 +315 +400

3 $280 + 355 +450

12 22 4 +315 +400 +500 ___- -

5 t-355 +450 +560

6 +400 $510 +630

--

2 +280 +330 +440

4 +335 $440 +530

5 +375 +475 +600

24 44

6 +425 +530 -1670

8 +475 +600 +750

10 +510 +630 +800

5 +400 +510 +630

6 +455 +575 +710

8 +500 +630 +800

46 90

10 +530 +670 +u50

12 $600 +750 +950

-

20 +710 +900 +1120

10 _t560 f710 +900

12 +630 +800 +1000

100 16 +710 + 900 +1120

-- 20 + 800 +1000 +1 200

*Lower limit is zero for all classes of accuracy.

7

IS : 12188.1987

6.1.3 Pitch ( lead ) accuracy - Pitch or lead accuracy of the lead screws shall be as indicated in Table 9.

. TABLE 9 TOLERANCE ON PITCH VALUES

-

Class of Accuracy

4 Tolerance on Tolerance on Pitch or Lead in pm f I

Each Individual Pitch or Lead * I- I

In w f

50 mm

2 5 -

4 IO

8 20

12 43 -

I Over Any Length of For Each Additional

I Lenath of 100 mm 300 mm 306 mm

6 9 3

12 20 5

25 30 10

50 70 20

-

- .

_-

_ -

For Entire Length

20

40

80

150

Note 1 -The error in pitch is generally measured over any length of 50 mm, 300 mm and the entire length. Tolerance values specified over 100 mm are for information only.

Note 2 -The values specified are the optimum under that particular class of accuracy. However, for different kinds of machine tools within that particular class of accuracy and for different lengths of lead screws, the values may slightly differ. In such cases, test chart accuracies are to be maintained.

6.1.4 Accuracy of the angle of fhe thread-The accuracy of the half-angle of the thread shall be as indicated in Table 10.

TABLE 10 TOLERANCE ON ANGLE OF THREAD

Class of Accuracy

1

2

3

4

Tolerance on Half-Angle of the Thread -- = ;

153 in Minutes for Pitch

2to5 mm 6 to 10 mm 12 to 20 mm

I f15 fl2 fl0

*20 ztl8 fl5

zb30 &25 *20

Not measured

6.2 Geometrical Accuracies

6.2.1 Cylindricity - Tolerance of cylindricity of pitch diameter of the lead screw is specified in Table 11.

6.2.2 Circularity -Tolerance of circularity of pitch diameter of the screw is specified in Table 12. The error is measured over one revolution when the screw laterally moves through a distance equal to the pitch.

8

IS i lZl88 a 1987

.

TABLE 11 TOLERANCE ON CYLINDRICITY

( Clause 6.2.1 )

I Nominal Diameter of Screw, mm

From I up to

Tolerance of Cylindricity in pm for Class of Accuracy of Screw

-I ‘I I I

t

30 I

50 I

12 j 20 ) 25 )

80 I 15 I 25 I 30 Not mea-

sured

I I I-I-I 80 1 100 I 20 I 30 I 40 I

100 I I - 25 40 I I

50

Note - Tolerance of cylindricity is applicab!e for the entire length of the threaded part of the lead screw. The values do not take into account the deflection due to self-weight. The error of cylindricity is half the difference between the minimum and the maximum pitch diameters measured.

TABLE 12 TOLERANCE ON CIRCULARITY

( Clause 6.2.2 )

Class of

i

Tolerance of Circularity in Accuracy pm for Pitch in mm

I 2 to 5

1 I 5

2 7

3 10

4 I 15

6 to 10 12 to 20

5 7

8 10

12 15

18 20

6.2.3 Radial runouf of fhe major diameter - Radial runout of the major diameter depends on functional accuracy of the screw and the type of bearings used. Designers shall specify the values for the permissible error of radial runout on the drawing, depending on the function,

IS : 12188.1987

6.3 Surface Finish of fhe Threads - Surface roughness RB, for the flanks of the thread and on the major diameter of thread shall be within the limits specified in Table 13.

. TABLE 13 SURFACE ROUGHNESS

Class of Accuracy

1

2

3

4

Surface Roughness Ra in pm

For Side Flanks of Threads of

I Screw Nut

For Major Diameter of

Screw Thread

0’2 0’4 1’6

O-4 0.8 1’6

0’8 1’6 1.6

0’8 1’6 3’2

10

IS :12188- 1987

APPENDIX A

( Clause 1.1 )

. MEASUREMENT OVER ROLLERS

( IS0 Metric Trapezoidal Screw Threads for Lead and Feed Screws)

9Dr

I

A

I 9d

I

dbr

All dimensions in millimetres.

Nominal Pitch Roller Measurement Dia Dia Over Rollers

Dr 2x dDr

-- 10 1 ‘626 10’628 -__ 12 1'625 12'625 16

2 1'10 1'622 16'622

20 1'620 20'620 1'615 25'615

; ~3~,.,,+-! ;;

12 2,541 12'541 -.-- - 16

4 2'05 2'537 16'537

18 2'530 18'530 20 2'525 I 20.525

--3o- 2'515 '30.515 22 3'103 22'603 24 -3.098- 24'598 --- - 25 3'096 25'596 26

28 5

2'55 3'093 26'593 3'090 -28.590-

30 ____ -30*587- 3'087 40 3'077 40'577 50 3'070 50*570- 16 4'410 17'410 20 4.408 21'408 30 4'397 31.397

-32 -4.393 _33;393 34 4.390 35.390-

-- 36 4'387 37.387- ~-

40 6 3'20 4.383 41'383 __~- __- 50 4'370 51'370 56 4'365 57'365 70 4.353 71'353 80 4'350 81.350 -~- 90 4'347 91.347 100 4'342 101'342

11

I

Nominal Pitch Dia

40 -- 44- -- 46 48 -- 50 8

52 -- 55

56 40 50 60

-63- 65 IO

-~ 70 _- 75 ~- 80 100 50 -- 60

-7o- -- 80

12

90 100 100 I 16 70 80

I 20

100

Roller Measurement Dia Over Rollers Dr

2x -I *.era

-I

dDr 40’558 A,,ICf

-

4’0

4'542 1 56'542 I 5'942 I 40'942

5’05

\

6.35

8'25

10'5

I-

d

-

5.936 --%0.936-

5’930 60'930 5’928 63 928 5'927 65'927 ~_ -_-__ 5'923 70.923

-~___ 5,920 75'920 ~-- 5'918 80.918~-

5.910-- 100'910 52~531

13'793 83’79 3 ~._ _. ~ - 13'791 103'791

Note -The tolerances for the dimensions dDr will be same as thosefordz.

IS : 12186 - 1987

EXPLANATORY NOTE

In the preparation of this standard, assistance has been derived from ON 200055 and CSN 254108 issued by the National Standards Body of Czechoslovakia.

12

Printed at New India Printing Press, Khurja, lndla