As 1275 Metric Threaded Fasteners

AS 1275—1985

Australian Standard� METRIC SCREW THREADS FOR FASTENERS ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 4 1 0 2 y a M 8 2 n o D T L Y T P G N I T L U S N O C R E D Y H y b d e s s e c c A

This Australian standard was prepared by Committee ME/28, Screw Threads. It was appro approve ved d on beha behalf lf of the Coun Counci cill of the S tanda tandards rds Associ Association ation of Austra Australia lia on 8 November 1984 and published on 4 April 1985.

The following interests interests are represen represented ted on Committee Committee ME/28: ME/28: Confederation Confederation of Australian Industry Industry CSIRO, Division of Applied Physics Department of Defence Department of Defence Support Department of Technical and Further Education, N.S.W. Electricity Electricity Supply Supply Associat Association ion of Australia Australia Fasteners Fasteners Institute Institute of Australia Australia Federal Chamber Chamber of Automotive Industries ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 4 1 0 2 y a M 8 2 n o D T L Y T P G N I T L U S N O C R E D Y H y b d e s s e c c A

Institution Institution of Engineers Engineers Australia Institution of Production Engineers Metal Metal Trades Trades Industry Industry Association Association of Australia Railways Railways of A ustralia ustralia Committee Committee Society of Automotive Engineers, Australasia

Review of Austr alia n Sta ndards. To keep abreast of progress progress in industry, industry, Australian Standards are subject to periodic periodic review review and are kept kept up to date date by the issue issue of amendmen amendments ts or new editions as necess necessary ary.. It is important therefore therefore that Standards Standards users users ensure ensure that they are in possession possession of the latest edition, and any amendments amendments thereto. thereto. Full details of all Australian Australian Standards Standards and related publications will be found in the Standards Standards Australia Catalogue of Publications; this information information is supplemented supplemented each month by t he magazine magazine ‘T he Australian Standard’, Standard’, which subscribing subscribing members members receive, receive, and which gives details of new publications, new editions editions and amendments, amendments, and of withdrawn Standards. Standards. Suggestions Suggestions for improvements improvements t o Australian Australian Standards, Standards, addressed addressed to the head office of Standards Australia, are welcomed. welcomed. N otification of any inaccuracy inaccuracy or ambiguity ambiguity found in an Australian Australian Standard should should be made without delay in order that the matter may be investigated and appropriate appropriate action taken.

This Standard was issued in draft form for comment as DR 83215.

AS 1275—1985

Australian Standard� METRIC SCREW THREADS FOR FASTENERS ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 4 1 0 2 y a M 8 2 n o D T L Y T P G N I T L U S N O C R E D Y H y b d e s s e c c A

First published (as AS B275) . . . . . . . . . . . . . . AS 1275 first published . . . . . . . . . . . . . . . . . . Second edition . . . . . . . . . . . . . . . . . . . . . . . .

1968 1972 1985

Incorporating: Amdt 1—1986

PUBLISHED BY ST ANDARDS AUSTRALIA (STANDARDS ASSOCIATION OF AUSTRALIA) 1 THE CRESCENT, HOMEBUSH, NSW 2140 ISBN 0 7262 3628 4

AS 1275—1985

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PREFACE This edition of this standard was prepared by the Association’s Committee on Screw Threads, to supersede AS 1275—1972. Since AS 1275 was first published, the major ISO standards dealing with metric screw threads (see later listing) have been revised, and are now in conflict with the information given in AS 1275—1972. This is particularly true with respect to the root curvature for external threads, and the limits specified for the t hread roots of both external and internal threads. A further important consideration i s that the ISO standards for metric screw threads are now being adopted virtually unchanged by most developed and developing countries, and therefore it is important that the Australian standards be aligned with their ISO counterparts as much as possible. This has been the aim in this edition of the standard. During the preparation of AS 1275 in the early 1970s, it was noted by the committee that the ISO symbols used for the various screw thread parameters were illogical, and so a more logical system was introduced in the Australian standards. T his was supported by sustained comment to ISO/TC1 proposing the A ustralian symbols. Unfortunately the Australian proposals were not accepted by ISO/TC1 and the original ISO symbols were retained. One of the major changes in this edition therefore has been to introduce the ISO symbology for the screw thread parameters. The other major change is with regard to the limits given for the thread roots on both external and internal threads. In AS 1275—1972 these limits were completely specified, whereas in the ISO standards only the minimum minor diameter is specified for external threads and the nominal (basic) major diameter is given for internal threads; the actual limits being indirectly controlled by the length of st raight f lanks. Furthermore a root curvature for external threads is only specified for threads intended for fasteners of property Class 8.8 and above. All other external threads may have a root configuration in accordance with the basic/design profile. ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 4 1 0 2 y a M 8 2 n o D T L Y T P G N I T L U S N O C R E D Y H y b d e s s e c c A

It was considered that the ISO approach on the limits for the thread roots was practical and should be adopted, because this would permit maximum f lexibility in manufacture without being unduly detrimental to either the strength of the screw thread or to its assembly properties. However, the ISO root curvature for external threads, taken t o the extreme could cause problems by introducing a notch effect, which may lead to fatigue failure in threads in some steels which have a high tensile level and/or have been severely cold worked. A cautionary statement to this effect has therefore been included in this standard. This standard has been based on and is in complete alignment with the following ISO standards: ISO 68—1973 ISO 261—1973

ISO General Purpose Screw Threads—Basic Profile ISO General Purpose Metric Screw Threads —General Plan

ISO 262—1973

ISO General Purpose Metric Screw Threads —Selected Sizes for Screws, Bolts and Nuts

ISO 724—1978

ISO Metric Screw Threads—Basic Dimensions

ISO 965/1—1980

ISO General Purpose Metric Screw Threads —Tolerances— Part 1: Principles and Basic Data

ISO 965/2—1980

ISO General Purpose Metric Screw Threads—Tolerances— Part 2: Limits of S izes f or General Purpose Bolt and Nut Threads—Medium Quality

ISO 965/3—1980

ISO General Purpose Metric Screw Threads —Tolerances— Part 3: Deviations for Constructional Threads

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AS 1275—1985

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CONTENTS Page

SECTION 1. SCOPE AND GENERAL 1.1 1.2 1.3 1.4 1.5 1.6 1.7

Sc ope . . . . . . . . . . . . Ap pli cat io n . . . . . . . . Re fer enced D ocum ents Def ini ti ons . . . . . . . . Sy mbol s . . . . . . . . . . Ver if icati on . . . . . . . Stress Area ( As) . . . .

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SECTION 2. SCREW THREAD PROFILES

) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 4 1 0 2 y a M 8 2 n o D T L Y T P G N I T L U S N O C R E D Y H y b d e s s e c c A

2.1 2.2 2.3 2.4 2.5 2.6

Sc ope o f Se cti on . . . . . . . . . Ba sic P ro fi le . . . . . . . . . . . . Max im um Mat er ia l Pr ofi le . . Le ast M at er ia l Pr ofi l e . . . . . Li mit i ng Pro fil es . . . . . . . . . Root Conto urs . . . . . . . . . .

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No tes on th e Pr oduc ti on o f E xt ern al T hr eads . . . . . . . . . . . . . . . Comparison of Symbols (Notations) for Screw Thread Parameters

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SECTION 3. DIMENSIONS AND TOLERANCES 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8

Sc ope o f Se cti on . . . . . . . Ba sic D im en si ons . . . . . . To ler ance P os it i ons . . . . . Fu ndam en ta l D ev ia ti ons . . To ler ance Gr ades . . . . . . To ler ance Cl ass es . . . . . . Li mit s of Si ze . . . . . . . . . Co ate d Th rea ds . . . . . . . .

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SECTION 4. DESIGNATION OF SCREW THREADS 4.1 4.2 4.3 4.4 4.5

Sc ope o f Se cti on . . . . . . . . . . . . . . . . . . . . . . . . . . . . Complete Designation for Internal Threads . . . . . . . . . Complete Designation for External Threads . . . . . . . . . Shortened Designation for Coarse Pitch Series Threads . De sig nat io n of a Thr ead F it . . . . . . . . . . . . . . . . . . . .

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APPENDICES A B

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STANDARDS ASSOCIATION OF AUSTRALIA Australian Standard for METRIC SCREW THREADS FOR FASTENERS

SECTION 1. SCOPE AND GENERAL 1.1 SCOPE. This standard specifies requirements for single start, parallel, coarse pitch series metric screw threads, mainly intended for threaded fasteners.

ISO 262

The standard covers screw threads from 1.6 mm diameter up to and including 64 mm diameter, in tolerance classes 6e, 6f, 6g and 8g, for external threads; and 6H and 6G for internal threads.

1.4 DEFINITIONS. For the purpose of this standard, the definitions given in AS XXXX apply.

The standard gives information on symbols for screw thread parameters, tolerances, deviations, thread classes, designation and verification. Appendices are included giving notes on the production of screw threads and a comparison of symbols used in this standard and the 1972 edition.

ISO General Purpose Metric Screw Threads—Selected Sizes for Screws, Bolts and Nuts

1.5 SYMBOLS. The symbols used in this standard to define the screw thread parameters are given in Table 1.1. NOTE: These are now aligned with the ISO symbols. For comparison of the current symbols with those used in AS 1275—1972, see Appendix B.

TABLE 1.1 SYMBOLS

NOTES:


1. The coarse pitch series given in this standard comprises the 1st and 2nd choice diameter/pitch combinations (for coarse pitch series threads) extracted from AS 1721. They are the same as those given in ISO 261 and ISO 262; the latter covering diameters up to and including 39 mm only. 2. For information on the bases of the metric screw thread system and associated formulas, see AS 1721.

1.2 AP PLI CAT IO N. This standard gives information on the design, manufacture and use of ISO coarse pitch series metric parallel screw threads.

Symbol D D 1 D 2 d d 1 d 2 P H R S

The standard is intended for adoption by industry and government authorities concerned with the design, manufacture and/or use of metric screw threads. 1.3 REFERENCED DOCUMENTS. The following standards are referred to in this standard: AS 1014

Gauging of Metric Screw Threads

AS 1098

Roller-type Screw Calliper Gauges

AS 1110

ISO Metric Hexagon Precision Bolts and Screws

AS 1111

ISO Metric Hexagon Commercial Bolts and Screws

AS 1112

ISO Metric Hexagon Nuts, including Thin Nuts, Slotted Nuts and Castle Nuts

AS 1214

H ot -dip G alv aniz ed C oat ings on Threaded Fasteners (ISO Metric Coarse Thread Series)

AS 1252

Hi gh- str en gt h S te el Associated Nuts and Structural Engineering

AS 1654

Limits and Fits for Engineering

AS 1721

General Purpose Metric Screw Threads

AS 1897

Electroplated Coatings on Threaded Components (Metric Coarse Seri es)

Bol ts wi th Washers for

AS XXXX* Glossary of Terms for Screw Threads IS O 261 IS O Ge ner al P ur pose Met ri c S cre w Threads—General Plan

N L T T D 1 T D 2 T d T d2 G, H e, f, g As

Explanation major diameter of internal thread minor diameter of internal thread pitch diameter of internal thread major diameter of external thread minor diameter of external thread pitch diameter of external thread

basic basic basic basic basic basic pitch height of fundamental triangle root radius of external thread designation f or lengths of thr ead engagement group Short designation f or lengths of thr ead engagement group Normal designation f or lengths of thr ead engagement group Long tolerance tolerance on minor diameter of internal thread tolerance on pitch diameter of external thread tolerance on major diameter of external thread tolerance on pitch diameter of external thread fundamental deviations for internal threads fundamental deviations for external thr eads nominal stress area (external threads)

1.6 VERIFICATION. The form and dimensions of screw threads to this standard should preferably be verified by gauging in accordance with AS 1014. The method(s) of verification (inspection) to be used on any particular occasion will however, depend on such things as the thread diameter, the thread class, the number of items produced and the method of manufacture. Where gauging is impractical, the threads may be verified by direct measurement or by optical methods; or a combination of both. 1.7 STRESS AREA ( A s). The cross-sectional area used for calculating the tensile and proof loads for threaded fasteners is based on the following formula:

NOTE: Calculated values of the stress areas are given in Table 3.3. * In course of preparation.

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SECTION 2. SCREW THREAD PROFILES 2.1 SCOPE OF SECTION. This Section specifies the basic profile, the maximum material profiles and the limiting profiles for external and internal metric screw threads. The section also includes information and values of the main elements used to derive the


basic and limiting thread profiles. 2.2 BASIC PROFILE. The basic profile of ISO general purpose metric screw threads is shown in Fig. 2.1. The dimensions for the various pitches are given in Table 2.1.

NOTE: For explanation of symbols, see Table 1.1.

Fig. 2.1. ISO BASIC PROFILE

TABLE 2.1 DIMENSIONS OF THE BASIC PROFILE millimetres Pitch P 0.35 0.4 0.45 0.5 0.6 0.7 0.75 0.8 1 1.25 1.5 1.75 2 2.5 3 3.5 4 4.5 5 5.5 6

H 0.303 0.346 0.389 0.433 0.519 0.606 0.649 0.692 0.866 1.082 1.299 1.515 1.732 2.165 2.598 3.031 3.464 3.897 4.330 4.763 5.196

/ H

5 8

109 410 711 013 615 218 519 820 025 532 038 544 051 063 076 089 102 114 127 140 152

0.189 0.216 0.243 0.270 0.324 0.378 0.405 0.433 0.541 0.676 0.811 0.947 1.082 1.353 1.623 1.894 2.165 2.435 2.706 2.976 3.247

443 506 570 633 760 886 949 013 266 582 899 215 532 165 798 431 063 696 329 962 595

/ H

3 8

0.113 0.129 0.146 0.162 0.194 0.227 0.243 0.259 0.324 0.405 0.487 0.568 0.649 0.811 0.974 1.136 1.299 1.461 1.623 1.786 1.948

666 904 142 380 856 332 570 808 760 949 139 329 519 899 279 658 038 418 798 177 557

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H /4 0.075 0.086 0.097 0.108 0.129 0.151 0.162 0.173 0.216 0.270 0.324 0.378 0.433 0.541 0.649 0.757 0.866 0.974 1.082 1.190 1.299

777 603 428 253 904 554 380 205 506 633 760 886 013 266 519 772 025 279 532 785 038

H /8 0.037 0.043 0.048 0.054 0.064 0.075 0.081 0.086 0.108 0.135 0.162 0.189 0.216 0.270 0.324 0.378 0.433 0.487 0.541 0.595 0.649

889 301 714 127 952 777 190 603 253 316 380 443 506 633 760 886 013 139 266 392 519

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2.3 MAXIMUM MATERIAL PROFILE. 2.3.1 Maximum material profile—internal thread. The profile of an external screw thread at its maximum material condition is shown in Fig. 2.2. It is the same as the basic profile except that in practice, t he root is rounded as shown by the dotted line, and cleared beyond a width P /8.


2.3.2 Maximum material profile—external thread. The profile of an external screw thread at its maximum material condition is shown in Fig. 2.3. It is the same as the basic profile, except that— (a) in practice the crests may be rounded inside the maximum profile as shown by the dotted line; and (b) the thread roots (minor diameter) may require to be modified in accordance with Clause 2.6.2.

Fig. 2.2. MAXIMUM MATERIAL PROFILE OF AN INTERNAL THREAD

NOTES: 1. 2.

3.

For details of root curvature, see Clause 2.6.2 and Fig. 2.7. The actual form of any rounding of the crests or roots of the thread will not be detected by conventional gauging since such gauges are cleared at the crest and root and only assess the straight flanks over the height of the basic profile, i.e. 5/8 H radial depth. If assessment of the root curvature is required, verification by optical projection is necessary and it is t o be stated in the design requirements.

Fig. 2.3. MAXIMUM MATERIAL PROFILE OF AN EXTERNAL THREAD

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2.4 LEAST MATERIAL PROFILE. The least material profile of both internal and external threads is derived from the maximum material profile using the information given in Section 3. 2.5 LIMITING PROFILES. 2.5.1 Limiting profiles—internal threads. Typical


limiting profiles for internal screw threads, involving tolerance positions H and G, are shown in Figs 2.4 and 2.5 respectively. 2.5.2 Limiting profiles—external threads. Typical limiting profiles for external screw threads, involving tolerance positions e, f and g, are shown in Fig. 2.6.

Fig. 2.4. LIMITING PROFILES FOR INTERNAL THREADS—TOLERANCE POSITION H

Fig. 2.5. LIMITING PROFILES FOR INTERNAL THREADS—TOLERANCE POSITION G

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AS 1275—1985


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Fig. 2.6. LIMITING PROFILES FOR EXTERNAL THREADS— TOLERANCE POSITIONS e, f AND g

2.6 ROOT CONTOURS.

and the minimum truncation is—

2.6.1 Internal threads. The actual root contour shall not at any point transgress the basic profile. In practice the taps used to produce internal threads will normally produce a rounded thread root cleared beyond a width of P /8 as shown in Fig. 2.2. 2.6.2 External threads. The actual root contour shall not at any point transgress the basic profile. However it is recommended that the root profile should not be flat, with sharp corners, but should be smoothly rounded. For threads on fasteners of property Class 8.8 and higher (see AS 1110 and AS 1252) and similar materials with similar properties, the root profile shall have a non-reversing curvature, no portion of which shall have a radius less than R min , which is tangential to t he t hr ead fl ank . T he r oot pr ofi l e m ay be comprised of arcs of minimum radius R min to which the flanks and a flat at the root are tangential (see Fig. 2.7). The values of R min are given in Table 2.2. The maximum truncation is—

0.125 P ≈ The above principle is recommended for all other ext er nal th re ads, par ti cul ar ly th ose use d i n applications subject to fatigue or impact. External threads must be accepted by a GO screw ring or GO screw calliper gauge. It is not practical to specify limits for the minor diameter of an external thread. A minimum minor diameter can be derived when the blend radius equals 0.125 P, and the flanks are at the least material condition, but as the flanks approach the maximum material condition the maximum minor diameter will tend to reduce, and the limiting values are dependent on the actual crest diameter and pitch diameter of the gauge as well as the subject screw thread (see Fig. 2.7). As noted in Fig. 2.3, conventional gauging will not examine the root contours and it is recommended that gauging be supplemented by profile projection of the external thread root.

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(a) Tolerance position h

(b) Tolerance positi ons e, f and g

Fig. 2.7. ROOT CONTOURS FOR BOLT THREADS (PROPERTY CLASS 8.8 AND HIGHER)

TABLE 2.2. MINIMUM ROOT RADII millimetres Pitch P 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.6 0.7 0.75 0.8 1 1.25 1.5 1.75 2 2.5 3 3.5 4 4.5 5 5.5 6

R min 0.025 0.031 0.038 0.044 0.050 0.056 0.063 0.075 0.088 0.094 0.100 0.125 0.156 0.188 0.219 0.250 0.313 0.375 0.438 0.500 0.563 0.625 0.688 0.750

NOTE: R min = 0.125 P .

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SECTION 3. DIMENSIONS AND TOLERANCES 3.1 SCOPE OF SECTION. This Section sets out the basic dimensions and thread tolerance system, and gives information on the tolerance grades, fundamental deviations, and tolerance classes used for ISO metric coarse pitch series threads.

Basic minor diameter d 1 = d - 2 × 5 / 8 H = D - 1.0825P

3.3 TOLERANCE POSITIONS. The following tolerance positions are given in this standard:

The Section also gives information on lengths of thread engagement applicable to the tolerance classes given in the standard.

(a) For internal threads: G with a positive fundamental deviation. H with zero fundamental deviation. See Figs 2.4 and 2.5.

NOTE: For further information on deviations and tolerances and their deviation, see AS 1721.

3.2 BASIC DIMENSIONS. Values for the basic pitch diameters and minor diameters are given in Table 3.1. The values rounded to the third decimal place have been calculated from the following formulas:

(b) For external threads: e, f and g with a negative fundamental deviation. 3.4 FUNDAMENTAL DEVIATIONS.

Basic pitch diameter

Fundamental deviations are 3.4 .1 G ene ral . designated by upper case letters for internal (nut) threads, and lower case letters for external (bolt) threads. The fundamental deviations for internal threads and for external threads, are positioned with respect to the basic size as shown in Fig. 3.1. For explanation of symbols, see Table 1.1.

D = D - 2 × 3 / 8 H = D - 0.6495P

Basic pitch diameter d 2 = d - 2 × 3 / 8 H = D - 0.6495P

Basic minor diameter D1 = D - 2 × 5 / 8 H = D - 1.0825P


Fig. 3.1. SCREW THREAD DEVIATIONS

TABLE 3.1 BASIC DIMENSIONS millimetres Basic major dia. First choice 1.6

Second choice 1.8

2 2.2 2.5 3 3.5 4 4.5 5 6

Pitch P

Basic pitch dia.

0.35 0.35 0.4 0.45 0.45 0.5 0.6 0.7 0.75 0.8 1

1.373 1.573 1.740 1.908 2.208 2.675 3.110 3.545 4.013 4.480 5.350

Basic Basic major dia. minor First Second dia. choice choice 1.221 8 1.421 10 1.567 12 1.713 14 2.013 16 2.459 18 2.850 20 3.242 20 3.688 24 4.134 27 4.917 30

Pitch P

Basic pitch dia.

1.25 1.5 1.75 2 2 2.5 2.5 2.5 3 3 3.5

7.188 9.026 10.863 12.701 14.701 16.376 18.376 20.376 22.051 25.051 27.727

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Basic Basic major dia. minor First Second dia. choice choice 6.647 33 8.376 36 10.106 39 11.835 42 13.835 45 15.294 48 17.294 52 19.294 56 20.752 60 23.752 64 26.211

Pitch P

Basic pitch dia.

Basic minor dia.

3.5 4 4 4.5 4.5 5 5 5.5 5.5 6

30.727 33.402 36.402 39.077 42.077 44.752 48.752 52.428 56.428 60.103

29.211 31.670 34.670 37.129 40.129 42.587 46.587 50.046 54.046 57.505

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3.4.2 Internal threads. The system provides two fundamental deviations for internal threads designated H and G. Values for the fundamental deviations are given in Table 3.2. The deviations are applicable to the pitch diameter and minor diameter, and should be algebraically added to the basic pitch diameter or basic minor diameter as relevant. 3.4.3 External threads. The system provides three fundamental deviations for external threads designated e, f and g. Values for the fundamental deviations are given in Table 3.2. The deviations are applicable to the pitch diameter and major diameter, and should be algebraically added to the basic pitch diameter or basic major diameter as relevant. 3.5 TOLERANCE GRADES. 3.5.1 General. This standard covers tolerance grades 6 and 8 for external (bolt) threads and tolerance grade 6 only for internal (nut) threads. The tolerances are applicable to the major diameter and pitch diameter, for external threads, and the pitch diameter and minor diameter, for internal threads. Values for the tolerance grades are given in Table 3.2. For information on the thread root tolerances, see Clause 3.5.2. 3.5.2 Root diameter tolerances. 3.5.2.1 Internal threads. As indicated in Clause 2.6.1, no specific tolerances are given for the major diameter ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 4 1 0 2 y a M 8 2 n o D T L Y T P G N I T L U S N O C R E D Y H y b d e s s e c c A

of internal threads. This parameter is considered acceptable, provided that no portion of the root curvature transgresses the basic profile. For convenience the minimum major diameter is given in the tabulated values of screw thread limits (see Table 3.3). 3.5.2.2 External threads. As indicated in Clause 2.6.2, no specific tolerances are given for the minor diameter of external threads. This parameter is considered acceptable, provided that the root curvature is in agreement with Clause 2.6.2 and the minimum minor diameter is not less than that specified for the appropriate tolerance class in Table 3.3. 3.6 TOLERANCE CLASSES. 3.6.1 General. The method of defining a tolerance class for ISO metric screw threads comprises two elements, and consists of a number describing the selected tolerance grade, followed by an upper or lower case letter describing the selected fundamental deviation— e.g. External threads: 6g 6h Internal threads: 6H 6G. NOTE: The tolerance class system for metric screw threads as given in this standard is similar but in no way related to the general system for limits and fits as given in AS 1654.

TABLE 3.2 TOLERANCES AND DEVIATIONS millimetres Basic major dia. D, d

Pitch P

Length of axial engagement N Over

1.6 1.8 * 2 2.2 * 2.5 3 3.5 * 4 4.5 * 5 6 8 10 12 14* 16 18* 20 22* 24 27* 30 33* 36 39* 42 45* 48 52* 56 60* 64 *

0.35 0.35 0.4 0.45 0.45 0.5 0.6 0.7 0.75 0.8 1 1.25 1.5 1.75 2 2 2.5 2.5 2.5 3 3 3.5 3.5 4 4 4.5 4.5 5 5 5.5 5.5 6

0.8 0.8 1 1.3 1.3 1.5 1.7 2 2.2 2.5 3 4 5 6 8 8 10 10 10 12 12 15 15 18 18 21 21 24 24 28 28 32

Up to 2.6 2.6 3 3.8 3.8 4.5 5 6 6.7 7.5 9 12 15 18 24 24 30 30 30 36 36 45 45 53 53 63 63 71 71 85 85 95

Internal threads

External threads Fundamental deviation

Grade 6

e

f

g

— — — — — 0.050 0.053 0.056 0.056 0.060 0.060 0.063 0.067 0.071 0.071 0.071 0.080 0.080 0.080 0.085 0.085 0.090 0.090 0.095 0.095 0.100 0.100 0.106 0.106 0.112 0.112 0.118

0.034 0.034 0.034 0.035 0.035 0.036 0.036 0.038 0.038 0.038 0.040 0.042 0.045 0.048 0.052 0.052 0.058 0.058 0.058 0.063 0.063 0.070 0.070 0.075 0.075 0.080 0.080 0.085 0.085 0.090 0.090 0.095

0.019 0.019 0.019 0.020 0.020 0.020 0.021 0.022 0.022 0.024 0.026 0.028 0.032 0.034 0.038 0.038 0.042 0.042 0.042 0.048 0.048 0.053 0.053 0.060 0.060 0.063 0.063 0.071 0.071 0.075 0.075 0.080

Tolerance

Major dia. 0.085 0.085 0.095 0.100 0.100 0.106 0.125 0.140 0.140 0.150 0.180 0.212 0.236 0.265 0.280 0.280 0.335 0.335 0.335 0.375 0.375 0.425 0.425 0.475 0.475 0.500 0.500 0.530 0.530 0.560 0.560 0.600

Pitch dia. 0.063 0.063 0.067 0.071 0.071 0.075 0.085 0.090 0.090 0.095 0.112 0.118 0.132 0.150 0.160 0.160 0.170 0.170 0.170 0.200 0.200 0.212 0.212 0.224 0.224 0.236 0.236 0.250 0.250 0.265 0.265 0.280

Second choice diameter.

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Grade 8 Major dia. — — — — — — — — — 0.236 0.280 0.335 0.375 0.425 0.450 0.450 0.530 0.530 0.530 0.600 0.600 0.670 0.670 0.750 0.750 0.800 0.800 0.850 0.850 0.900 0.900 0.950

Pitch dia. — — — — — — — — — 0.150 0.180 0.190 0.212 0.236 0.250 0.250 0.265 0.265 0.265 0.315 0.315 0.335 0.335 0.355 0.355 0.375 0.375 0.400 0.400 0.425 0.425 0.450

Fundamental deviation H G + 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

0.019 0.019 0.019 0.020 0.020 0.020 0.021 0.022 0.022 0.024 0.026 0.028 0.032 0.034 0.038 0.038 0.042 0.042 0.042 0.048 0.048 0.053 0.053 0.060 0.060 0.063 0.063 0.071 0.071 0.075 0.075 0.080

Tolerance Grade 6 Minor dia. 0.100 0.100 0.112 0.125 0.125 0.140 0.160 0.180 0.190 0.200 0.236 0.265 0.300 0.335 0.375 0.375 0.450 0.450 0.450 0.500 0.500 0.560 0.560 0.600 0.600 0.670 0.670 0.710 0.710 0.750 0.750 0.800

Pitch dia. 0.085 0.085 0.090 0.095 0.095 0.100 0.112 0.118 0.118 0.125 0.150 0.160 0.180 0.200 0.212 0.212 0.224 0.224 0.224 0.265 0.265 0.280 0.280 0.300 0.300 0.315 0.315 0.335 0.335 0.355 0.355 0.375

AS 1275—1985

12

TABLE 3.3 LIMITING DIMENSIONS FOR METRIC COARSE PITCH SERIES SCREW THREADS millimetres


*

External threads

Basic major dia. D, d

Pitch P

1.6

0.35

1.8

0.35

2

0.4

2.2 *

0.45

2.5

0.45

3

0.5

3.5 *

0.6

4

0.7

4.5 *

0.75

5

0.8

6

1

8

1.25

10

1.5

12

1.75

14 *

2

16

2

18

2.5

20

2.5

22 *

2.5

Tolerance class 6g 6f 6g 6f 6g 6f 6g 6f 6g 6f 6g 6f 6e 6g 6f 6e 6g 6f 6e 6g 6f 6e 6g 8g 6f 6e 6g 8g 6f 6e 6g 8g 6f 6e 6g 8g 6f 6e 6g 8g 6f 6e 6g 8g 6f 6e 6g 8g 6f 6e 6g 8g 6f 6e 6g 8g 6f 6e 6g 8g 6f 6e


Major diameter

Internal threads

Pitch diameter

Minor Stress diameter area As

max.

mi n.

max.

mi n.

1.581 1.566 1.781 1.766 1.981 1.966 2.180 2.165 2.480 2.465 2.980 2.964 2.950 3.479 3.464 3.447 3.978 3.962 3.944 4.478 4.462 4.444 4.976 4.976 4.962 4.940 5.974 5.974 5.960 5.940 7.972 7.972 7.958 7.937 9.968 9.968 9.955 9.933 11.966 11.966 11.952 11.929 13.962 13.962 13.948 13.929 15.962 15.962 15.948 15.929 17.958 17.958 17.942 17.920 19.958 19.958 19.942 19.920 21.958 21.958 21.942 21.920

1.496 1.481 1.696 1.681 1.886 1.871 2.080 2.065 2.380 2.365 2.874 2.858 2.844 3.354 3.339 3.322 3.838 3.882 3.804 4.338 4.322 4.304 4.826 4.740 4.812 4.790 5.794 5.694 5.780 5.760 7.760 7.637 7.746 7.725 9.732 9.593 9.719 9.697 11.701 11.541 11.687 11.664 13.682 13.512 13.668 13.649 15.682 15.512 15.668 15.649 17.623 17.428 17.607 17.585 19.623 19.428 19.607 19.585 21.623 21.428 21.607 21.585

1.354 1.339 1.554 1.539 1.721 1.706 1.888 1.873 2.188 2.173 2.655 2.639 2.625 3.089 3.074 3.057 3.523 3.507 3.489 3.991 3.975 3.957 4.456 4.456 4.442 4.420 5.324 5.324 5.310 5.290 7.160 7.160 7.146 7.125 8.994 8.994 8.981 8.959 10.829 10.829 10.815 10.792 12.663 12.663 12.649 12.630 14.663 14.663 14.649 14.630 16.334 16.334 16.318 16.296 18.334 18.334 18.318 18.296 20.334 20.334 20.318 20.296

1.291 1.276 1.491 1.476 1.654 1.639 1.817 1.802 2.117 2.102 2.580 2.564 2.550 3.004 2.989 2.972 3.433 3.417 3.399 3.901 3.885 3.867 4.361 4.306 4.347 4.325 5.212 5.144 5.198 5.178 7.042 6.970 7.028 7.007 8.862 8.782 8.849 8.828 10.679 10.593 10.665 10.642 12.503 12.413 12.489 12.470 14.503 14.413 14.489 14.470 16.164 16.069 16.148 16.126 18.164 18.069 18.148 18.126 20.164 20.069 20.148 20.126

Tolerance

Major diameter min.

min.

mm 2

class

1.075 1.060 1.275 1.260 1.408 1.393 1.539 1.524 1.839 1.824 2.272 2.256 2.242 2.635 2.620 2.603 3.002 2.986 2.968 3.439 3.423 3.405 3.868 3.814 3.854 3.834 4.597 4.528 4.583 4.563 6.272 6.200 6.258 6.237 7.938 7.858 7.925 7.903 9.602 9.516 9.588 9.565 11.271 11.181 11.257 11.238 13.271 13.181 13.257 13.238 14.624 14.529 14.608 14.586 16.624 16.529 16.608 16.586 18.624 18.529 18.608 18.586

1.27

5.03

6H 6G 6H 6G 6H 6G 6H 6G 6H 6G 6H 6G

6.78

8.78

min.

1.600 1.600 1.800 1.800 2.000 2.000 2.200 2.200 2.500 2.500 3.000 3.000

1.458 1.477 1.658 1.677 1.830 1.849 2.003 2.023 2.303 2.323 2.775 2.795

1.373 1.392 1.573 1.592 1.740 1.759 1.908 1.928 2.208 2.228 2.675 2.695

1.321 1.340 1.521 1.540 1.679 1.698 1.838 1.858 2.138 2.158 2.599 2.619

1.221 1.240 1.421 1.440 1.567 1.586 1.713 1.733 2.013 2.033 2.459 2.479

6H 6G

3.500 3.500

3.222 3.243

3.110 3.131

3.010 3.031

2.850 2.871

6H 6G

4.000 4.000

3.663 3.685

3.545 2.576

3.422 3.444

3.242 3.264

6H 6G

4.500 4.500

4.131 4.153

4.013 4.035

3.078 3.900

3.688 3.710

14.2

6H 6G

5.000 5.000

4.605 4.629

4.480 4.504

4.334 4.358

4.134 4.158

20.1

6H 6G

6.000 6.000

5.500 5.526

5.350 5.376

5.153 5.179

4.917 4.943

36.6

6H 6G

8.000 8.000

7.348 7.376

7.188 7.216

6.912 6.940

6.647 6.675

58.0

6H 6G

10.000 10.000

9.206 9.238

9.026 9.058

8.676 8.708

8.376 8.408

84.3

6H 6G

12.000 11.063 10.863 12.000 11.097 10.897

10.441 10.106 10.475 10.140

115

6H 6G

14.000 12.913 12.701 14.000 12.951 12.739

12.210 11.835 12.248 11.873

157

6H 6G

16.000 14.913 14.701 16.000 14.951 14.739

14.210 13.835 14.248 13.873

192

6H 6G

18.000 16.656 16.376 18.000 16.642 16.418

15.854 15.294 15.786 15.336

245

6H 6G

20.000 18.600 18.376 20.000 18.642 18.418

17.744 17.294 17.786 17.336

303

6H 6G

22.000 20.600 20.376 22.000 20.642 20.418

19.744 19.294 19.786 19.336

2.07 2.48 3.39

11.3

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Minor diameter

max.

1.7

Pitch diameter

max.

min.

(continued)

AS 1275—1985

13

TABLE 3.3 (continued) millimetres Basic major dia. D, d


Pitch P

24

3

27 *

3

30

3.5

33 *

3.5

36

4

39 *

4

42

4.5

45 *

4.5

48

5

52 *

5

56

5.5

60 *

5.5

64

*

External threads

6

Major diameter

Internal threads

Pitch diameter

Minor Stress Tolerdiameter area As ance class mi n. mm 2

Tolerance class

max.

min.

max.

min.

6g 8g 6f 6e 6g 8g 6f 6e 6g 8g 6f 6e 6g 8g 6f 6e 6g 8g 6f 6e 6g 8g 6f 6e 6g 8g 6f 6e 6g 8g 6f 6e 6g 8g 6f 6e 6g 8g 6f 6e 6g 8g 6f 6e 6g 8g 6f 6e 6g 8g 6f 6e

23.952 23.952 23.937 23.915 26.952 26.952 26.937 26.915 29.947 29.947 29.930 29.910 32.947 32.947 32.930 32.910 35.940 35.940 35.925 35.905 38.940 38.940 38.825 38.905 41.937 41.937 41.920 41.900 44.937 44 937 44.920 44.900 47.929 47.929 47.915 47.894 51.929 51.929 51.915 51.894 55.925 55.925 55.910 55.888 59.925 59.925 59.910 59.888 63.920 63.920 63.905 63.882

23.577 23.352 23.562 23.540 26.577 26.352 26.562 26.540 29.522 29.277 29.505 29.485 32.522 32.277 32.505 32.485 35.465 35.190 35.450 35.430 38.455 38.190 38.450 38.430 41.437 41 137 41.420 41.400 44.437 44.137 44.420 44.400 47.399 47.079 47.385 47.364 51.399 51.079 51.385 51.364 55.365 55.025 55.350 55.328 59.365 59.025 59.350 59.328 63.320 62.970 63.305 63.282

22.003 22.003 21.988 21.966 25.003 25.003 24.988 24.966 27.674 27.674 27.657 27.637 30.674 30.674 30.657 30.637 33.342 33.342 33.327 33.307 36.342 36.342 36.327 36.307 39.014 39.014 38.997 38.977 42.014 42.014 41.997 41.977 44.681 44.681 44.667 44.646 48.681 46.681 48.667 48.646 52.353 52.353 52.338 52.316 56.353 56.353 56.338 56.316 60.023 60.023 60.008 59.985

21.803 21.688 21.788 21.766 24.803 24.688 24.788 24.766 27.462 27.339 27.445 27.425 30.462 30.339 30.445 30.425 33.118 32.987 33.103 33.083 36.118 35.987 36.103 36.083 38.778 38.639 38.761 38.741 41.778 41.639 41.761 41.741 44.431 44.281 44.417 44.396 48.431 48.281 48.417 48.396 52.088 51.928 52.073 52.051 56.088 55.928 56.073 56.051 59.743 59.573 59.728 59.705

19.955 19.840 19.940 19.918 22.955 22.840 22.940 22.918 25.305 25.182 25.288 25.268 28.305 28.182 28.288 28.268 30.654 30.523 30.639 30.619 33.654 33.523 33.639 33.619 36.006 35.876 35.989 35.969 39.066 38.867 38.989 38.969 41.351 41.201 41.337 41.316 45.351 45.201 45.337 45.316 48.700 48.540 48.685 48.663 52.700 52.540 52.685 52.663 56.047 55.877 56.032 56.009

Major diameter min.

Pitch diameter max.

min.

Minor diameter max.

mi n.

353

6H 6G

24.000 24.000

22.316 22.051 22.364 22.099

21.252 21.300

20.752 20.800

459

6H 6G

27.000 27.000

25.316 25.051 25.364 25.099

24.252 24.300

23.752 23.800

561

6H 6G

30.000 30.000

28.007 27.727 28.060 27.780

26.771 26.824

26.211 26.264

694

6H 6G

33.000 33.000

31.007 30.727 31.060 30.780

29.771 29.824

29.211 29.264

817

6H 6G

36.000 36.000

33.702 32.402 33.762 33.462

32.270 32.330

31.670 31.730

976

6H 6G

39.000 39.000

36.702 35.402 36.762 36.462

35.270 35.330

34.670 34.730

1121

6H 6G

42.000 42.000

39.392 39.077 39.455 39.140

37.799 37.862

37.129 37.192

1306

6H 6G

45.000 45.000

42.392 42.077 42.455 42.140

40.799 40.862

40.129 40.192

1473

6H 6G

48.000 48.000

45.087 44.752 45.158 44.823

43.297 43.368

42.587 42.658

1758

6H 6G

52.000 52.000

49.087 48.752 49.158 48.823

47.297 47.368

46.587 46.658

2030

6H 6G

56.000 56.000

52.783 52.428 52.858 52.503

50.796 50.871

50.046 50.121

2362

6H 6G

60.000 60.000

56.783 56.428 56.858 56.503

54.796 54.871

54.046 54.121

2676

6H 6G

64.000 64.000

60.478 60.103 60.558 60.183

58.305 58.385

57.505 57.585


COPYRIGHT

AS 1275—1985

14

The 3.6.2 Disposition of tolerance classes. tolerance classes are disposed about the basic pitch and major diameter for external threads and the basic pitch and minor diameter for internal threads as shown in Fig. 3.2.

Based on the above, the following combinations are recommended:

3.6.3 Selection of tolerance classes.

(b) Precision quality fasteners—6H nut with 6g bolt.

3.6.3.1 General. The tolerance classes for the pitch and crest diameter, shall be selected in accordance with Clause 3.6.3.3, bearing in mind the type of fastener, i.e. ‘precision’ or ’ commercial’ quality. 3.6.3.2 Length of axial thread engagement. The tolerance classes given in this standard are intended for the ‘normal’ length of thread engagement as given in Ta bl e 3.2. If t he a ct ual le ngt h of th read engagement is unknown (as i n the manufacturing of st anda rd bolt s), th e n orm al le ngt h of th read engagement shall be assumed. NOTE: For further information, see AS 1721.

3.6.3.3 Recommended combinations. Although there is no di re ct gui dance giv en by I SO fo r t he combination of thread classes, these may be inferred by reference to the appropriate ISO standards for threaded fasteners.


(a) Commercial quality fasteners—6H nut with 8g bolt.

NOTE: Tolerance classes 6e, 6f and 6G, are essentially provided for ‘preplated’ screw thread dimensions.

3.7 LIMITS OF SIZE. The limiting dimensions for external threads, tolerance classes 6e, 6f, 6g and 8g; and internal threads, tolerance classes 6H and 6G are given in Table 3.3. 3.8 COATED THREADS. The limiting dimensions given in Table 3.3 apply to the screw threads before coating, unless otherwise specified. After coating the actual thread profile shall not transgress the maximum material limits, i.e. the basic dimensions as given in Table 3.1. The above provisions apply to all coated screw threads except those hot- dip galvanized in accordance with AS 1214. NOTE: For further i nformation on electroplated coatings on threaded components, see AS 1897.

Fig. 3.2. RELATIVE POSITION OF TOLERANCE CLASSES

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AS 1275—1985

15

SECTION 4. DESIGNATION OF SCREW THREADS 4.1 SCOPE OF SECTION. This Section sets out the designation system used for metric screw threads for f asteners, and gives the complete designation, together with a shortened designation which may be applied to coarse pitch series threads as covered by this standard. Provision is also made for designating different types of fits between internal and external threads.

4.3 COMPLETE DESIGNATION FOR EXTERNAL THREADS. The complete designation for an external screw thread with the same tolerance class for the pitch diameter and major diameter comprises the same elements in the same order as given for internal screw threads (see Clause 4.2).

4.2 COMPLETE DESIGN ATION FO R INTERNAL THREADS. The complete designation of an internal screw thread to this standard comprises the following elements in the following order:

Thread designation symbol

(a) The letter M indicating an ISO Metric general purpose screw thread.

Pitch diameter tolerance class

(b ) Th e v al ue o f t he b asi c m aj or d ia met er in millimetres.

4.4 SHORTENED DESIGNATION FOR COARSE PITCH SERIES THREADS. The designation for coarse pitch series internal and external threads is the same as that given in Clauses 4.2 and 4.3 respectively, except that the indication of pitch may be omitted. Therefore if no pitch is indicated in the designation, a coarse pitch series thread is specified, i.e.—

(c) The value of the pitch in millimetres. (d) The tolerance class designation for the pitch diameter.

EXAMPLE:

Basic major diameter Pitch

M8 × 1 - 6g | | | | | | | | | | | | | | | | | | | |

NOTE: For coarse pitch series threads, see also Clause 4.4.

M8 — 6e is the same as M8 × 1.25 - 6e; and ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 4 1 0 2 y a M 8 2 n o D T L Y T P G N I T L U S N O C R E D Y H y b d e s s e c c A

EXAMPLE: Thread designati on symbol Basic major diameter Pitch Pitch diameter tolerance class

M5 × 0.8 - 5H | | | | | | | | | | | | | | | | | | | |

NOTE: For coarse pitch series threads, see also Clause 4.4.

M5 — 5H is the same as M5 × 0.8 - 5H. 4.5 DESIGNATION OF A THREAD FIT. A fit between mating internal and external threads is indicated in the designation by the tolerance class of the internal thread, followed by the tolerance class for the external thread separated by an oblique stroke. Example: M8 - 6H/6g

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AS 1275—1985

16

APPENDIX A

NOTES ON THE PRODUCTION OF EXTERNAL THREADS The actual form of the crest of an external thread depends on the method of manufacture. If a single-ribbed grinding wheel or single-point cutting tool is used, a thread with a completely flat crest will be produced, as illustrated in Fig. A1(a). Use of a crushed multi-ribbed wheel produces a crest profile similar to that shown in Fig. A1(b). A typical form of crest produced by the thread rolling processes is shown in Fig. A1(c). The crests of threads resulting from this process will normally fall wholly above the minimum limiting profile shown in Figs 2.6 and 2.7. Fig. A1(d) shows the form of crest produced by a thread cutting die of nominal root radius, viz 125 P . With a correctly formed tool, there will be no serious loss of straight flank even when it cuts a thread on minimum diameter. Provided that due care is taken in regard to the wear of tools, rounded crests should rarely reach the dotted profile shown in Fig. 2.3. It may be mentioned that the following advantages are associated with bolts with rounded crests: (a) Bolts with rounded crests are l ess susceptible to damage by burring in handling and transport than those having flat crests, which result in sharp, or semi-sharp, edges round the outside diameter of the bolt.


(b) Troubles associated with plating are far less serious if the crests of the bolts are rounded. In the plating of bolts by the usual barrel plating process, the burring of flat-crested bolts can be quite serious, and in the still-vat process the plating tends to build up round the two edges at the outside diameter and encroaches upon the flanks.

(a ) C re st pr oduced b y gr in di ng w it h a sin gl e- ri bbed wheel or cutt in g with a single point tool.

(b ) C re st pr oduced b y gr in di ng w it h a cru shed mu lt i- ri bbed w heel .

(c ) C re st p ro du ced by th re ad -r ol li ng

(d ) C re st pr oduced b y a t hr ea d cutting die.

Fig. A1. CREST PROFILES RESULTING FROM DIFFERENT PRODUCTION METHODS COPYRIGHT

AS 1275—1985

17

APPENDIX B

COMPARISON OF SYMBOLS (Notations) FOR SCREW THREAD PARAMETERS Symbol (notation) used in Parameter


AS 1275—1972

ISO and this standard

Major diameter — basic internal threads external threads

D Dn D s

D; d — —

Pitch diameter — basic internal threads external threads

E E n E s

d 2; d 2 —

Minor diameter — basic internal threads external threads

d d n d s

D 1; d 1 — d 3 *

Pitch Height of fundamental triangle

p H

P H

Height (depth) of thread — basic internal threads external threads

h hn hs

— — —

Addendum — basic internal threads external threads

h ”n h ′s

Dedendum — basic internal threads external threads

h′n h ”s

— —

Truncation at minor diameter — basic internal threads external threads

t t n t s

— — —

Truncation at major diameter — basic internal threads external threads

T T n T s

Width of flat at minor diameter — basic internal threads external threads

— —

f f n f s

— — —

F F n F s

— — —

Radius at minor diameter—external threads

r s

R

Radius at major diameter—internal threads

Rn

—

C n C s

— —

T En T Es

T D 2 T d

T Dn T Ds

— T d

T dn T ds

T 1D

A s Ac

A s

AS s AS n

— —

Width of flat at major diameter — basic internal threads external threads

Height of circular segments at rounded roots — internal threads external threads Tolerances for pitch diameter — i nternal threads external threads Tolerances for major diameter — internal threads external threads Tolerances for minor diameter — internal threads external threads Areas of stress calculation

Tension

External threads cross-section — stress areas core area

Sh ea r

Ex te rn al th re ad h eli x Internal thread helix

Deviations—general symbols

Fundamental d eviation series

Internal threads — lower upper

ln un

External threads — lower upper

ls us

Internal threads ( L n) External threads ( U s)

Radial engagement NOTE: The following additional symbols are used in the ISO standards but not in this standard: EI = lower deviation for internal threads ES = upper deviation for internal threads ei = lower deviation for external threads es = upper deviation for external threads

COPYRIGHT

2

—

H, G h, g, e

H; G; h; g; e; f

Re

—

This page has been left intentionally blank. ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 4 1 0 2 y a M 8 2 n o D T L Y T P G N I T L U S N O C R E D Y H y b d e s s e c c A

As 1275 Metric Threaded Fasteners

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