1、BRITISH STANDARD BS 5346:1976 Incorporating Amendment Nos. 1, 2 and 3 Specification for ISO metric trapezoidal screw threads UDC 621.882.082.1:621.882.082.4BS5346:1976 This British Standard, having been prepared under the directionof the Mechanical Engineering Industry StandardsCommittee was publish
2、ed under the authority ofthe Executive Board on 28May1976 BSI 02-2000 The following BSI references relate to the work on this standard: Committee reference MEE/1 and MEE/1/9 Draft for comment 72/37746 DC ISBN 0 580 09462 6 Co-operating organizations The Mechanical Engineering Industry Standards Comm
3、ittee, under whose supervision this British Standard was prepared, consists of representatives from the following Government departments and professional and industrial organizations. The organizations marked with an asterisk in the above list, together with the following, were directly represented
4、on the committee entrusted with the preparation of this British Standard. Associated Offices Technical Committee Engineering Equipment Users Association Association of Consulting Engineers Federation of Manufacturers of Construction Association of Hydraulic Equipment Equipment and Cranes Manufacture
5、rs Ltd Health and Safety Executive (HM Factory Association of Mining Electrical and Inspectorate) Mechanical Engineers Institution of Gas Engineers British Compressed Air Society Institution of Heating and Ventilating British Electrical and Allied Manufacturers Engineers Association Institution of M
6、echanical Engineers British Gas Corporation Institution of Plant Engineers British Gear Manufacturers Association Institution of Production Engineers British Internal Combustion Engine London Transport Executive Manufacturers Association Machine Tool Trades Association* British Mechanical Engineerin
7、g Confederation Ministry of Defence* British Pump Manufacturers Association National Coal Board British Steel Corporation National Engineering Laboratory British Steel Industry Department of Industry Crown Agents for Oversea Governments and Process Plant Association Administrations Railway Industry
8、Association of Great Britain Department of the Environment Royal Institute of British Architects Department of Industry Society of Motor Manufacturers and Traders Department of Trade Ltd Electricity Supply Industry in England and Wales Telecommunication Engineering and Manufacturing Association Brit
9、ish Valve Manufacturers Association Screw thread Tool Manufacturers Association Gauge and Tool Makers Association Society of British Aerospace Companies Ltd Amendments issued since publication Amd. No. Date of issue Comments 3552 December 1981 5095 June 1986 5507 June 1987 Indicated by a sideline in
10、 the marginBS5346:1976 BSI 02-2000 i Contents Page Co-operating organizations Inside front cover Foreword ii 1 Scope 1 2 Reference 1 3 Definitions 1 4 Maximum material profiles 4 5 Diameter/pitch combinations 4 6 Nominal sizes 4 7 Length of thread engagement 4 8 Tolerances, grades and positions 5 9
11、Designation 7 10 Multiple-start threads 22 11 Inspection 22 12 Coated threads 22 Appendix A Formulae 23 Figure 1 Basic profile 1 Figure 2 Nominal profile 2 Figure 3 Profiles for threads with clearance on the crest and on the flank 3 Figure 4 External threads with tolerance positions c and e 14 Figur
12、e 5 Internal threads with tolerance position H 14 Figure 6 Tolerance position with respect to zero line (basic size) 15 Figure 7 Lead and pitch of multiple-start thread 22 Table 1 Dimensions for basic profile 2 Table 2 Dimensions for the thread profile 4 Table 3 Diameter/pitch combinations 6 Table 4
13、 Diameters of threads 8 Table 5 Length of thread engagement 12 Table 6 Tolerance symbols 13 Table 7 Tolerance grades 13 Table 8 Minor diameter tolerances of internal threads (T D1 ) 15 Table 9 Major diameter tolerances of external threads (T d ) 16 Table 10 Fundamental deviations for the pitch diame
14、ter of internal and external threads 17 Table 11 Recommended tolerance classes 17 Table 12 Minor diameter tolerance of external thread (T d3 ). Limits of tolerance 18 Table 13 Pitch diameter tolerance of internal thread (T D2 ) 19 Table 14 Pitch diameter tolerance of external thread (T d2 ) 20 Table
15、 15 Pitch diameter tolerance of external thread (T d2 ). Limits of tolerance 21 Table 16 Factors for tolerances for the pitch diameters of multiple-start threads 22 Table 17 Factors for pitch diameter tolerance for internal thread 24 Publication referred to Inside back coverBS5346:1976 ii BSI 02-200
16、0 Foreword This British Standard has been prepared under the authority of the Mechanical Engineering Industry Standards Committee, and specifies ISO metric trapezoidal screw threads from8mm to300mm in diameter. The standard is based on International Standards ISO2901, ISO 2902, ISO 2903 andISO 2904
17、published in October1977 by the International Organization for Standardization (ISO), which specify the basic profile, the general plan, tolerances, and nominal sizes respectively for ISO metric trapezoidal screw threads. The tolerance system in this standard is based on that for ISO general purpose
18、 metric screw threads and reflects ISOR965-1, complete with tolerance positions c and e for pitches above6mm, but with different values. Formulae for the calculation of fundamental deviations and tolerances are given inAppendix A to this standard. A British Standard does not purport to include all t
19、he necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii
20、, pages1 to 24, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS5346:1976 BSI 02-2000 1 1 Scope This British Standard specifies the requireme
21、nts for ISO metric trapezoidal screw threads from8mm to300mm in diameter. Single-start and multiple-start threads are included in the details for designation and tolerances. A tolerance system is specified but it does not apply to threads with special requirements for axial displacement, e.g. lead s
22、crews. 2 Reference The title of the British Standard referred to in this standard is shown on the inside back cover. 3 Definitions For the purposes of this British Standard the following thread form definitions apply. 3.1 basic profile the basic profile is the theoretical profile associated with the
23、 basic sizes of the major, pitch and minor diameters of the thread. The deviations are applied to these basic sizes (SeeTable 1 andFigure 1.) 3.2 basic size the theoretical size to which the deviations are applied in order to obtain the limits of size 3.3 nominal size the size which is used for gene
24、ral identification. It is generally the basic major diameter of the thread Figure 1 Basic profileBS5346:1976 2 BSI 02-2000 Table 1 Dimensions for basic profile Dimensions are in millimetres. Pitch P H 1.866 P H/ 2 0.933 P H 1 0.5 P 0.366 P 1.5 2 3 2.799 3.732 5.598 1.400 1.866 2.799 0.75 1 1.5 0.549
25、 0.732 1.098 4 5 6 7.464 9.330 11.196 3.732 4.665 5.598 2 2.5 3 1.464 1.830 2.196 7 8 9 13.062 14.928 16.794 6.531 7.464 8.397 3.5 4 4.5 2.562 2.928 3.294 10 12 14 18.660 22.392 26.124 9.330 11.196 13.062 5 6 7 3.660 4.392 5.124 16 18 20 29.856 33.588 37.320 14.928 16.794 18.660 8 9 10 5.856 6.588 7
26、.320 22 24 28 41.052 44.784 52.248 20.526 22.392 26.124 11 12 14 8.052 8.784 10.248 32 36 40 44 59.712 67.176 74.640 82.104 29.856 33.588 37.320 41.052 16 18 20 22 11.712 13.176 14.640 16.104 Figure 2 Nominal profileBS5346:1976 BSI 02-2000 3 NOTE 1It is recommended to provide for a rounding or a cha
27、mfer max. 0.5a cat the major diameter of the external threads. NOTE 2In case of manufacture by rolling, the profile at the minor diameter can be modified in order to obtain a rounding on the root of the thread. The minor diameter d 3of the external thread must in this case be reduced by0.15P. Figure
28、 3 Profile for threads with clearance on the crest and the flankBS5346:1976 4 BSI 02-2000 Table 2 Dimensions for the thread profile 4 Maximum material profiles These profiles have prescribed clearances on the major, minor, and pitch diameter referring to the basic profile. Should modifications to th
29、ese profiles become necessary due to the particular methods of fabrication, they shall be agreed between the customer and the manufacturer, (SeeTable 2 andFigure 2 andFigure 3.) 5 Diameter/pitch combinations Table 3 gives the standard series of nominal diameters and their associated pitches. The nom
30、inal diameters are classified as first, second and third choice and are specified in columns1, 2 and3 respectively. The diameters in column3 shall not be used for new designs. The preferred pitches for any diameter are shown within the frames inTable 3. 6 Nominal sizes Nominal sizes of the screw thr
31、eads are shown inTable 4. 7 Length of thread engagement Lengths of thread engagement are given inTable 5 and are classified into groups designated “normal” (N) and “long” (L), depending on the number of threads engaged for a given basic major diameter. Dimensions are in millimetres. P a c h 3 H 1 H
32、4 R 1max. R 2max. 1.50 2 3 0.15 0.25 0.25 0.9 1.25 1.75 0.75 1 1.5 0.9 1.25 1.75 0.08 0.13 0.13 0.15 0.25 0.25 4 5 6 0.25 0.25 0.5 2.25 2.75 3.5 2 2.5 3 2.25 2.75 3.5 0.13 0.13 0.25 0.25 0.25 0.5 7 8 9 0.5 0.5 0.5 4 4.5 5 3.5 4 4.5 4 4.5 5 0.25 0.25 0.25 0.5 0.5 0.5 10 12 14 0.5 0.5 1 5.5 6.5 8 5 6
33、7 5.5 6.5 8 0.25 0.25 0.5 0.5 0.5 1 16 18 20 1 1 1 9 10 11 8 9 10 9 10 11 0.5 0.5 0.5 1 1 1 22 24 28 1 1 1 12 13 15 11 12 14 12 13 15 0.5 0.5 0.5 1 1 1 32 36 40 44 1 1 1 1 17 19 21 23 16 18 20 22 17 19 21 23 0.5 0.5 0.5 0.5 1 1 1 1BS5346:1976 BSI 02-2000 5 8 Tolerances, grades and positions 8.1 Tole
34、rance symbols are shown inTable 6. Recommended tolerance classes are shown inTable 11. For the minor diameter tolerances of internal threads (T D1 ) and the major diameter tolerances of external threads (T d ) there is only one tolerance grade, i.e. 4. Values are given inTable 8 andTable 9 respectiv
35、ely. Values for the pitch diameter tolerance of internal threads (T D2 ) are given inTable 13 and for external threads (T d2 ) inTable 14. 8.2 The tolerances do not apply to trapezoidal screw threads with special requirements for axial displacement, e.g. lead screws. 8.3 Tolerance grades shall be as
36、 shown inTable 7. 8.4 Tolerance positions are invariably H for internal threads with zero fundamental deviation. 8.4.1 Tolerance positions for the pitch diameter of external threads are c and e where the fundamental deviation is negative. The tolerance position for the major diameters of external th
37、reads is h with zero fundamental deviation. Fundamental deviations are shown inTable 10. Tolerance positions are shown graphically inFigure 4, Figure 5 andFigure 6. 8.4.2 Limits of tolerance values (pitch diameter tolerance positions c and e for the minor diameter tolerance of external threads (T d3
38、 ) and the pitch diameter tolerance of external threads (T d2 ) are given inTable 12 andTable 15 respectively. 8.5 Tolerances for multiple-start threads are the same as those for single-start with the exception of the pitch diameter tolerances which are multiplied by the factors shown inTable 16.BS5
39、346:1976 6 BSI 02-2000 Table 3 Diameter/pitch combinations Dimensions are in millimetres. Nominal diameter Pitches col 1 col 2 col 3 44 40 36 32 28 24 22 20 18 16 14 12 10 9 8 7 6 5 4 3 2 1.5 8 1.5 10 9 2 2 1.5 1.5 11 3 2 12 14 3 3 2 2 16 20 18 4 4 4 2 2 2 24 22 26 8 8 8 5 5 5 3 3 3 28 8 5 3 3 3 32
40、30 10 10 6 6 36 34 10 10 10 6 6 3 3 3 38 7 40 44 42 12 10 10 7 7 7 3 3 3 48 46 50 12 12 12 8 8 8 3 3 3 52 12 8 3 60 55 14 14 9 9 3 3 70 65 75 16 16 16 10 10 10 4 4 4 80 16 10 4 90 85 18 18 12 12 4 4 100 95 105 20 20 18 12 12 12 4 4 4 110 20 12 4 120 115 22 22 14 14 6 6 130 125 135 24 22 22 14 14 14
41、6 6 6 140 145 24 24 14 14 6 6 150 24 16 6 160 155 165 28 28 24 16 16 16 6 6 6 170 175 28 28 16 16 8 6 180 28 18 8 185 32 18 8 190 32 18 8 195 32 18 8 200 32 18 8 220 210 36 36 20 20 8 8 230 36 20 8 240 250 40 36 22 22 12 8 260 40 22 12 280 270 40 40 24 24 12 12 300 290 44 44 24 24 12 12BS5346:1976 B
42、SI 02-2000 7 9 Designation The complete designation for a screw thread comprises a designation for the thread system and size and a designation for the thread tolerance. The single-start metric trapezoidal screw threads conforming to this standard shall be designated by the letters Tr followed by th
43、e value of the nominal diameter and of the pitch expressed in millimetres and separated by the sign . Example: Tr 40 7 The multiple-start metric trapezoidal screw threads conforming to this British Standard shall be designated by the letters Tr followed by the values of the nominal diameter and of t
44、he lead for the multiple-start threads, separated by the sign , and, in brackets, the letter P and the value of the pitch (distance between two neighbouring ridges), all expressed in millimetres. Each tolerance designation comprises: a figure indicating the grade of the pitch diameter tolerance a le
45、tter indicating the position of the pitch diameter tolerance; capital for internal threads, lower case for external threads. Example for internal threads, 40 mm diameter Tr 40 7 7H Example for external threads, 40 mm diameter Tr 40 7 7e A fit between threaded parts is indicated by the internal threa
46、d tolerance designation followed by the external thread tolerance designation separated by a stroke. Example for a40mm diameter2-start thread: For left-hand metric trapezoidal screw threads conforming to this British Standard, the letters LH shall be added to the thread designation. Example: Tr 40 1
47、4 (P7) LH Example: Tr 40 14 (P7) (Number of starts = ) (see Figure 7) Lead Pitch -BS5346:1976 8 BSI 02-2000 Table 4 Diameters of threads Dimensions are in millimetres. Nominal diameter d Pitch P Pitch diameter d 2= D 2 Major diameter D 4 Minor diameter d 3 D 1 column 1 column 2 column 3 8 1.5 7.250
48、8.300 6.200 6.500 9 1.5 2 8.250 8.000 9.300 9.500 7.200 6.500 7.500 7.000 10 1.5 2 9.250 9.000 10.300 10.500 8.200 7.500 8.500 8.000 11 2 3 10.000 9.500 11.500 11.500 8.500 7.500 9.000 8.000 12 2 3 11.000 10.500 12.500 12.500 9.500 8.500 10.000 9.000 14 2 3 13.000 12.500 14.500 14.500 11.500 10.500
49、12.000 11.000 16 2 4 15.000 14.000 16.500 16.500 13.500 11.500 14.000 12.000 18 2 4 17.000 16.000 18.500 18.500 15.500 13.500 16.000 14.000 20 2 4 19.000 18.000 20.500 20.500 17.500 15.500 18.000 16.000 22 3 5 8 20.500 19.500 18.000 22.500 22.500 23.000 18.500 16.500 13.000 19.000 17.000 14.000 24 3 5 8 22.500 21.500 20.000 24.500 24.500 25.000 20.500 18.500 15.000 21.000 19.000 16.000 26 3 5 8 24.500 23.500 22.000 26.500 26.500 27.000 22.500 20.500 17.000 23.000 21.000
