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1、BRITISH STANDARD BS 2779:1986 Specification for Pipe threads for tubes and fittings where pressure-tight joints are not made on the threads (metric dimensions) UDC 621.643.414:621.882.082.1 Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 08:58:50 GMT+00:00 2006,
2、 Uncontrolled Copy, (c) BSI BS 2779:1986 This British Standard, having been prepared under the direction of the Piping Systems Components Standards Committee, was published under the authority of the Board of BSI and comes into effect on 29 August 1986 BSI 12-1998 First published December 1956 First
3、 revision April 1973 Second revision August 1986 The following BSI references relate to the work on this standard: Committee reference PSE/9 Draft for comment 85/75381 DC ISBN 0 580 15212 X Committees responsible for this British Standard This British Standard was entrusted by the Piping Systems Com
4、ponents Standards Committee (PSE/-) to Technical Committee PSE/9, upon which the following bodies were represented: Association of Hydraulic Equipment Manufacturers British Compressed Air Society British Engine Group of the Society of Motor Manufacturers and Traders British Gas Corporation British H
5、ydromechanics Research Association British Malleable Tube Fittings Association British Steel Industry British Valve Manufacturers Association Ltd. Copper Tube Fittings Manufacturers Association Department of Trade and Industry (National Engineering Laboratory) Energy Industries Council Engineering E
6、quipment and Materials Users Association Gauge and Tool Makers Association Institution of Civil Engineers Institution of Gas Engineers Institution of Public Health Engineers Institution of Water Engineers and Scientists Water Authorities Association Water Companies Association Wrought Fitting Makers
7、 Association Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 08:58:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2779:1986 BSI 12-1998i Contents Page Committees responsibleInside front cover Fo
8、rewordii 1Scope1 2Symbols1 3Classification and designation1 4Thread details4 Appendix A Special truncated form of the Whitworth thread for class A external threads5 Appendix B Notes on tolerancing system structure5 Appendix C Method of verification of thread size and form by means of limit gauges6 A
9、ppendix D Gauges for the method given in appendix C8 Figure 1 Thread profile and tolerance zones4 Figure 2 Special truncated external thread5 Figure 3 NOT GO screw calliper gauge7 Figure 4 Start of complete thread8 Figure 5 Chamfer of start of thread8 Figure 6 Thread profiles of GO ring gauges and t
10、heir check plugs9 Figure 7 Relative positions of pitch diameter tolerance zones for GO ring gauges and their check plugs10 Figure 8 Thread profiles of NOT GO ring gauges and their check plugs and calliper gauges11 Figure 9 Relative positions of pitch diameter tolerance zones for NOT GO ring gauges,
11、calliper gauges and their check plugs12 Figure 10 Thread profiles of Go and NOT GO plug gauges13 Figure 11 Relative positions of pitch diameter tolerance zones for GO and NOT GO plug gauges14 Table 1 Basic dimensions and tolerances3 Table 2 Special truncated fastening threads, class A external threa
12、ds5 Table 3 Dimensions for GO and NOT GO gauges and their check plugs for class A external threads and for GO gauges and their check plugs for class B external threads9 Table 4 Other values for GO and NOT GO gauges and their check plugs for class A and class B external threads as a function of the p
13、itch, P10 Table 5 Dimensions for NOT GO gauges and their check plugs for class B external threads11 Table 6 Dimensions for threaded GO and NOT GO plug gauges13 Table 7 Other values for GO and NOT GO plug gauges as a function of the pitch, P14 Publications referred toInside back cover Licensed Copy:
14、London South Bank University, London South Bank University, Tue Dec 12 08:58:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2779:1986 ii BSI 12-1998 Foreword This revision of BS 2779 has been prepared under the direction of the Piping Systems Components Standards Committee. It supersedes BS 2779:1
15、973, which is withdrawn. This standard is based on and is technically equivalent to the two Parts of ISO 228 “Pipe threads where pressure-tight joints are not made on the threads”, namely ISO 228/1-1982 “Designation, dimensions and tolerances”, and ISO/2-1980 “Verification by means of limit gauges”;
16、 both Parts are published by the International Organization for Standardization (ISO). This standard provides a range of thread sizes which are considered to be necessary to fulfil general requirements. Dimensions are given in metric units only. For ease of production, it has been found convenient t
17、o reproduce the figures from ISO 228/2-1980 for Figure 4, Figure 5, Figure 7, Figure 10 and Figure 11 of this standard. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with
18、 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, pages 1 to 14, an inside back cover and a back cover. This standerd has been updated (see copyright date) and may have had amen
19、dments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 08:58:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2779:1986 BSI 12-19981 1 Scope This British Standard specifies re
20、quirements for the designation and dimensions of Whitworth form fastening pipe threads having a thread size designation in the range 1/16 to 6 inclusive. This standard applies to pipe threads where pressure-tight joints are not made on the threads1). Dimensions are given in metric units. The toleran
21、ce on the crests of the threads allows for truncation (see 4.1). NOTE 1The pipe threads covered by this standard are generally used for fastening purposes, such as the mechanical assembly of the component parts of fittings, cocks and valves, etc. NOTE 2The titles of the publications referred to in t
22、his standard are listed on the inside back cover. 2 Symbols For the purposes of this British Standard, the following symbols apply. 3 Classification and designation 3.1 Classes of external and internal threads For internal threads, one class of tolerance on the pitch diameter has been provided. For
23、external threads, two classes of tolerance on the pitch diameter have been established, as follows: a) class A tolerance, entirely negative value equivalent to the internal thread tolerance (see Table 1); b) class B tolerance, entirely negative value twice that of the class A tolerance (see Table 1)
24、. NOTE 1Where no class reference is stated, class B should be assumed. NOTE 2The tolerance zones are shown in Figure 1. NOTE 3The choice of fit for a particular purpose rests with the purchasers designer. 1) Reference should be made to BS 21 for requirements for pipe threads where pressure-tight joi
25、nts are made on the threads. SymbolTerm b3Width of clearance groove at the major and minor diameter of the thread profile with shortened flanks. dBasic major diameter of the external thread. d1Basic minor diameter of the external thread (d1 = d 1.280 654P). d2Basic pitch diameter of the external thr
26、ead (d2 = d 0.640 327 P). DBasic major diameter of the internal thread (D = d). D1Basic minor diameter of the internal thread (D1 = D 1.280 654P = d1). D2Basic pitch diameter of the internal thread (D2 = D 0.640 327P = d2). hHeight of the thread profile with rounded crests and roots. HHeight of the
27、triangle of the thread profile. mDistance between the middle of the tolerance zone TR of the threaded ring gauge and the middle of the tolerance zone TCP of the GO check plug. PPitch. rRadius of rounded crests and roots. sDisplacement of the clearance groove with shortened flanks. STolerance on b3.
28、TcpTolerance on the pitch diameter of GO and NOT GO threaded check plugs and wear check plugs. TdTolerance on the basic major diameter of the external thread. Td2Tolerance on the basic pitch diameter of the external thread. TD1Tolerance on the basic minor diameter of the internal thread. TD,2Toleran
29、ce on the basic pitch diameter of the internal thread. TPLTolerance on the pitch diameter of GO and NOT GO threaded plug gauges. TRTolerance on the pitch diameter of GO and NOT GO threaded ring gauges. uA length equal to twice the radial height of rounding at crest of root and thread (u = 0.147 84P)
30、. WGOAverage amount available for the permissible wear of GO threaded plug gauge and GO threaded ring gauge. WNGAverage amount available for the permissible wear of NOT GO threaded plug gauge and NOT GO threaded ring gauge. ZPLDistance between the middle of the tolerance zone TPL of the GO threaded
31、plug gauge and the lower limit of the thread. ZRDistance between the middle of the tolerance zone TR of the GO threaded ring gauge and the upper limit of the thread. Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 08:58:50 GMT+00:00 2006, Uncontrolled Copy, (c)
32、BSI BS 2779:1986 2 BSI 12-1998 3.2 Designation Internal and external threads shall be designated by the letter “G” followed by the thread size designation given in Table 1, and, for external threads, the class reference: for example, G for an internal thread, G A for a class A external thread, and G
33、 B for a class B external thread. NOTEWhere no class reference is stated, class B should be assumed. Where threads are full form (see 4.1.2), the letter “F” shall be added to the designation, e.g. G F for internal threads and G AF for class A external threads. Where external threads have the special
34、 truncated Whit-worth form in accordance with Table 2, the letter “T” shall be added to the designation, e.g. G AT. Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 08:58:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2779:1986 BSI 12-19983 Table 1 Basic dimens
35、ions and tolerances 12345678910111213141516 Thread size designation Number of threads in 25.4 mm Pitch Depth of thread, Basic diameters Tolerances on the basic pitch diameterb Tolerance on the basic minor diameter Tolerance on the basic major diameter Internal thread, TD2External thread, Td2Internal
36、 thread, TD1External thread, Td Ph Major d = D Pitch d2 = D2 Minor d1= D1 Lower deviation Upper deviation Lower deviation, class A Lower deviation, class B Upper deviation Lower deviation Upper deviation Lower deviation Upper deviation mmmmmmmmmmmmmmmmmmmmmmmmmmmm a1/16 280.907 0.5817.7237.1426.561
37、0+ 0.107 0.107 0.21400+ 0.282 0.2140 a1/8 280.907 0.5819.7289.1478.566 0+ 0.107 0.107 0.21400+ 0.282 0.2140 a1/4 191.337 0.85613.15712.30111.445 0+ 0.125 0.125 0.25000+ 0.445 0.2500 a3/8 191.337 0.85616.66215.80614.950 0+ 0.125 0.125 0.25000+ 0.445 0.2500 a1/2141.814 1.16220.95519.79318.631 0+ 0.142
38、 0.142 0.28400+ 0.541 0.2840 5/8 141.814 1.16222.91121.74920.587 0+ 0.142 0.142 0.28400+ 0.541 0.2840 a3/4 141.814 1.16226.44125.27924.117 0+ 0.142 0.142 0.28400+ 0.541 0.2840 7/8 141.814 1.16230.20129.03927.877 0+ 0.142 0.142 0.28400+ 0.541 0.2840 a1 112.309 1.47933.24931.77030.291 0+ 0.180 0.180 0
39、.36000+ 0.640 0.3600 11/8 112.309 1.47937.89736.41834.939 0+ 0.180 0.180 0.36000+ 0.640 0.3600 a11/4 112.309 1.47941.91040.43138.952 0+ 0.180 0.180 0.36000+ 0.640 0.3600 a11/2112.309 1.47947.80346.32444.845 0+ 0.180 0.180 0.36000+ 0.640 0.3600 13/4 112.309 1.47953.74652.26750.788 0+ 0.180 0.180 0.36
40、000+ 0.640 0.3600 a2 112.309 1.47959.61458.13556.656 0+ 0.180 0.180 0.36000+ 0.640 0.3600 a21/4 112.309 1.47965.71064.23162.752 0+ 0.217 0.217 0.43400+ 0.640 0.4340 a21/2 112.309 1.47975.18473.70572.226 0+ 0.217 0.217 0.43400+ 0.640 0.4340 23/4 112.309 1.47981.53480.05578.576 0+ 0.217 0.217 0.43400+
41、 0.640 0.4340 a3 112.309 1.47987.88486.40584.926 0+ 0.217 0.217 0.43400+ 0.640 0.4340 31/2 112.309 1.479100.33098.85197.372 0+ 0.217 0.217 0.43400+ 0.640 0.4340 a4 112.309 1.479113.030 111.551 110.072 0+ 0.217 0.217 0.43400+ 0.640 0.4340 41/2 112.309 1.479125.730 124.251 122.772 0+ 0.217 0.217 0.434
42、00+ 0.640 0.4340 a5 112.309 1.479138.430 136.951 135.472 0+ 0.217 0.217 0.43400+ 0.640 0.4340 51/2 112.309 1.479151.130 149.651 148.172 0+ 0.217 0.217 0.43400+ 0.640 0.4340 a6 112.309 1.479163.830 162.351 160.872 0+ 0.217 0.217 0.43400+ 0.640 0.4340 a Preferred sizes. b For thin walled parts, the to
43、lerances on pitch diameters apply to the mean pitch diameter, which is the arithmetical mean of two diameters measured at right angles to each other. Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 08:58:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2779:1986
44、 4 BSI 12-1998 4 Thread details 4.1 Form of thread 4.1.1 The basic form of the thread shall be the basic Whitworth form, as shown in Figure 1. NOTEThis form is identical with that specified for the parallel thread in BS 21. 4.1.2 For internal threads, the crests of the thread shall have one of the f
45、ollowing forms: a) the full form, as shown in Figure 1; or b) the truncated form, with crests truncated to the tolerances given in Table 1. NOTEThe form of thread should be agreed between the manufacturer and the purchaser. 4.1.3 For external threads, the crests of the thread shall have one of the f
46、ollowing forms: a) the full form, as shown in Figure 1; or b) the truncated form, with crests truncated to the tolerances given in Table 1; or c) for class A threads only, the special truncated form, in accordance with appendix A. NOTEThe special truncated form of thread is used where galling of the
47、 threads may occur. 4.2 Dimensions and tolerances 4.2.1 Dimensions. The basic dimensions for the threads shall be as given in Table 1, except for class A external threads with the special truncated form see 4.1.3 c). 4.2.2 Tolerances. Tolerances for the major, pitch and minor diameters shall be as g
48、iven in Table 1, except for class A external threads with the special truncated form see 4.1.3 c). NOTE 1Reference should be made to appendix B for further information on the tolerancing system structure. Tolerance zones are shown in Figure 1. NOTE 2The tolerances for the basic pitch diameter of int
49、ernal threads given in Table 1 correspond to the positive deviation of the tolerances on the diameter specified in BS 21, with the exception of the tolerances for the following thread size designations, for which slightly higher tolerances have been specified: 1/16, 1/8, 1/4, 3/8, 21/2, 3, 4, 5, and 6. 4.3 Compliance NOTENo method is specified for verification of compliance with the requirements of 4.1 and 4.2, but the method described in appen
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