当前位置:首页 >> 机械/仪表 >>

BS 2.1 英国管螺纹标准(公制)


BRITISH STANDARD

BS 21:1985
Reprinted, incorporating Amendment No. 1

Specification for

Pipe threads for tubes and fittings where pressure-tight joints ar

e made on the threads (metric dimensions)

621.643.414 – 762.4:621.882.082.22

BS 21:1985

Committees responsible for this British Standard
The preparation of this British Standard was entrusted by the Piping Systems 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 Gas Corporation British Hydromechanics Research Association British Internal Combustion Engine Manufacturers’ Association British Malleable Tube Fittings Association British Steel Industry British Valve Manufacturers’ Association Ltd. Department of Trade and Industry (National Engineering Laboratory) Energy Industries Council Engineering Equipment 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’ Association

This British Standard, having been prepared under the direction of the Piping Systems Standards Committee, was published under the authority of the Executive Board and comes into effect on 30 September 1985 ? BSI 03-1999 First published April 1905 First revision November 1909 Second revision November 1938 Third revision December 1957 Fourth revision March 1973 Fifth revision September 1985 The following BSI references relate to the work on this standard: Committee reference PSE/9 Draft for comment 83/78475 DC ISBN 0 580 14556 5

Amendments issued since publication Amd. No. 6633 Date of issue December 1990 Comments Indicated by a sideline in the margin

BS 21:1985

Contents
Committees responsible Foreword 1 2 3 4 5 6 Scope Definitions Symbols Basic forms of pipe threads Jointing threads Longscrew threads Page Inside front cover ii 1 1 2 2 3 4 10 15 15 1 3 4 5 7 8 10 10 12 12 12 12 6 9 11 13 14 16

Appendix A Recommended gauging systems for jointing threads Appendix B Methods of verification of jointing thread dimensions and form using recommended gauging systems described in Appendix A Appendix C Special parallel external threads for gas appliances where pressure-tight seals are made on machined faces Figure 1 — Terms relating to pipe threads Figure 2 — Basic Whitworth form Figure 3 — Basic form of taper pipe thread Figure 4 — Typical designs illustrating internal taper or parallel pipe threads complying with 5.1 Figure 5 — System A screw gauges assembled respectively with threads of maximum and minimum sizes Figure 6 — System B screw gauges assembled respectively with threads of maximum and minimum sizes Figure 7 — Taper full-form screw plug gauge (system A) Figure 8 — Taper full-form screw ring gauge (system A) Figure 9 — Taper full-form screw plug gauge (system B) Figure 10 — Taper full-form screw ring gauge (system B) Figure 11 — Taper plain plug gauge (system B) Figure 12 — Taper plain ring gauge (system B) Table 1 — Lengths for dimension A in Figure 4 Table 2 — Basic dimensions and limits of size Table 3 — Dimensions of taper full-form screw plug and ring gauges for system A Table 4 — Dimensions of taper full-form screw and taper plain plug and ring gauges for system B Table 5 — Manufacturing tolerances for gauges for systems A and B Table 6 — Special parallel external threads for gas appliances where pressure-tight seals are made on machined faces Publications referred to

Inside back cover

? BSI 03-1999

i

BS 21:1985

Foreword
This revision of BS 21 has been prepared under the direction of the Piping Systems Standards Committee and supersedes BS 21:1973 which is withdrawn. The basic thread is that given in ISO 7/1-1982 published by the International Organization for Standardization (ISO) but this standard also includes requirements for longscrew threads and for thread forms, and recommended methods of gauging threads, given in the previous edition of BS 21. The implementation of ISO 7/2-1982 has not been considered necessary as the dimensional and geometrical controls imposed by the ISO gauging system are available through the BS 21:1973 gauging system, which has been retained in this edition. This edition of this standard relates to metric dimensions only. 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 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 16, 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. ii
? BSI 03-1999

BS 21:1985

1 Scope
This British Standard specifies requirements for the following pipe threads. a) Jointing threads, which are pipe threads for joints made pressure-tight by the mating of the threads and are taper external, taper internal or parallel internal threads.
NOTE 1 Parallel external pipe threads are not suitable as jointing threads.

NOTE 4 The titles of the publications referred to in this standard are listed on the inside back cover.

2 Definitions
For the purposes of this British Standard the following definitions apply (see Figure 1). 2.1 gauge diameter the basic major diameter of the thread, whether external or internal, at the gauge plane 2.2 gauge plane the plane, perpendicular to the axis, at which the major cone has the gauge diameter
NOTE When there is a chamfer at the start of the thread not exceeding one pitch in length the gauge plane is theoretically located for internal threads at the face of the thread, and for external threads at a distance equal to the basic gauge length from the small end of the thread.

b) Longscrew threads, which are parallel pipe threads used for longscrews (connectors) specified in BS 1387 where a pressure-tight joint is achieved by the compression of a soft material on to the surface of the external thread by tightening a backnut against a socket. Thread sizes from 1? 16 to 6 inclusive are covered by this standard and requirements for thread forms, dimensions and tolerances are given, together with the designation of each type of thread.
NOTE 2 Appendix B gives methods of verification of jointing thread dimensions and form using recommended gauging systems described in Appendix A. NOTE 3 Reference should be made to BS 2779 for requirements for pipe threads where pressure-tight joints are not made on the threads.

2.3 gauge length on an external thread, the distance parallel to the axis, from the gauge plane to the small end of the thread

NOTE

For symbols see clause 3.

Figure 1 — Terms relating to pipe threads

? BSI 03-1999

1

BS 21:1985

2.4 complete thread that part of the thread which is fully formed at both crest and root
NOTE When there is a chamfer at the start of the thread not exceeding one pitch in length, it is included in the length of complete thread.

3 Symbols
For the purposes of this British Standard, the following symbols apply.
Symbol Term

H h

2.5 incomplete thread that part of the thread which is fully formed at the root but truncated at the crest by its intersection with the cylindrical surface of the product 2.6 washout thread that part of the thread which is not fully formed at the root
NOTE The washout thread is produced by the bevel at the start of the threading tool.

r p d d1 d2 T1 T2

Height of the triangle of the thread profile perpendicular to the thread axis Height of the thread profile between rounded crests and roots perpendicular to the thread axis Radius of rounded crests and roots Pitch Gauge diameter (basic major diameter) of the thread at the gauge plane Basic minor diameter of the thread at the gauge plane (d1 = d – 1.280 654p) Basic pitch diameter of the thread at the gauge plane (d2 = d – 0.640 327p) Tolerance on the position of the gauge plane on external threads (see Figure 1) Tolerance on the position of the gauge plane relative to the face of internally tapered threads

2.7 vanish cone an imaginary cone the surface of which would pass through the roots of the washout thread 2.8 major cone an imaginary cone which just touches the crests of a taper external thread or the roots of a taper internal thread 2.9 useful thread the complete thread and the incomplete thread, excluding the washout thread 2.10 total thread the complete thread, the incomplete thread and the washout thread 2.11 fitting allowance the length of useful thread beyond the gauge plane of an external thread required to provide for assembly with an internal thread at the upper limit of the tolerance 2.12 wrenching allowance the length of useful thread which is provided to accommodate the relative movement between the pipe end and the internally threaded part required for wrenching beyond the position of hand engagement

NOTE Additional symbols are used in Table 1, Table 3, Table 4 and Table 5; these are not defined because they are for reference purposes only when used in conjunction with Figure 4, Figure 7, Figure 8, Figure 9, Figure 10, Figure 11 and Figure 12.

4 Basic forms of pipe threads
4.1 Parallel threads The basic form of the parallel internal pipe thread and of the parallel external longscrew thread shall be the basic Whitworth form as follows. The Whitworth thread form (see Figure 2) is that of a symmetrical V-thread in which the angle between the flanks, measured in an axial plane section, is 55°; one-sixth of this sharp V is truncated at the top and the bottom, the threads being rounded equally at crests and roots by circular arcs blending tangentially with the flanks, the theoretical depth of thread being 0.640 327 times the nominal pitch. The basic thread depth, calculated from this, is rounded off to the nearest 0.001 mm.

2

? BSI 03-1999

BS 21:1985

Figure 2 — Basic Whitworth form 4.2 Taper threads The basic form of the taper pipe thread shall be as follows (see Figure 3). It is based on the Whitworth thread form and it too has an angle of 55°, the flanks making equal angles with the axis. The crests and roots are rounded off symmetrically in such a manner as to give the same basic differences between major, pitch and minor diameters as in the Whitworth thread of the same nominal pitch. The taper is 1 in 16, measured on the diameter. If tested in accordance with Appendix A and Appendix B, the threads shall be deemed to comply with this standard if they are in accordance with the following. a) For system A: 1) when gauging taper external pipe threads with the taper full-form screw ring gauge, the small end of the thread shall lie within the plus and minus tolerance T1/2 (column 9 of Table 2) of the face of the small end of the ring gauge (see Figure 5); 2) when gauging taper or parallel internal pipe threads with the taper full-form screw plug gauge, the end of the thread shall lie within the plus and minus tolerance T2/2 (column 17 of Table 2) from the gauge plane step of the plug gauge (see Figure 5). b) For system B: 1) when gauging taper external pipe threads with the taper full-form screw ring gauge or with the taper plain ring gauge, the small end of the thread shall lie between the faces or flush with either face of the step on the gauge (see Figure 6); 2) when gauging taper or parallel internal pipe threads with the taper full-form screw plug gauge or with the taper plain plug gauge, the end of the thread shall lie between the faces or flush with either face of the step on the gauge (see Figure 6).

5 Jointing threads
5.1 General The design of internally threaded parts (see Figure 4) shall be such that they can receive pipe ends up to the lengths given in column 13 of Table 2 and the minimum lengths of useful thread shall be not less than 80 % of the values given in column 14 of Table 2.
NOTE It is common practice to apply a jointing medium to the threads before assembly to ensure that a pressure-tight joint is made.

5.2 Compliance
NOTE No method is specified for verification of jointing thread dimensions and form but the methods described in Appendix B, using the gauging systems described in Appendix A, are recommended.

? BSI 03-1999

3

BS 21:1985

NOTE

The taper is 1 in 16 measured on the diameter (shown exaggerated in the diagram).

Figure 3 — Basic form of taper pipe thread 5.3 Parallel internal pipe threads 5.3.1 Dimensions and tolerances. The basic diameters of parallel internal threads shall be as given in columns 5, 6, and 7 of Table 2 and the tolerances shall be as given in column 18 of Table 2. 5.3.2 Designation. Parallel internal threads shall be designated by the letters RP, together with the thread size. These screw threads shall be referred to on drawings and related documents in the following manner: RP? 5.4 Taper external and taper internal pipe threads 5.4.1 Dimensions and tolerances. The dimensions and tolerances of taper external threads shall be as given in Table 2. The basic diameters of taper internal threads shall be as given in columns 5, 6 and 7 of Table 2 and the tolerances shall be as given in column 17 of Table 2. 5.4.2 Designation. Taper external pipe threads shall be designated by the letter R and taper internal threads by the letter RC, together with the thread size. These screw threads shall be referred to on drawings and related documents in the following manner: external taper: R? internal taper: RC?

6 Longscrew threads
6.1 General Longscrew threads shall be as specified in 6.2 and 6.3 except for longscrew threads for gas appliances where pressure-tight seals are made on machined faces, where special longscrew threads shall be used as specified in Appendix C.

4

? BSI 03-1999

BS 21:1985

NOTE 1 NOTE 2

The useful thread of the internally threaded part is to be not less than 80 % of the length given in column 14 of Table 2. The taper is shown exaggerated in the diagrams.

Figure 4 — Typical designs illustrating internal taper or parallel pipe threads complying with 5.1

? BSI 03-1999

5

BS 21:1985

Table 1 — Lengths for dimension A in Figure 4
Thread size designation Minimum lengths A in turns of thread (see note) for: Internal thread with extreme plus tolerance (maximum diameter) (mm)
1? 16

Internal thread of basic size (gauge diameter) (mm)

Internal thread with extreme minus tolerance (minimum diameter) (mm)

1

/8

1

/4

81/8 (7.4) 81/8 (7.4) 81/4 (11.0) 8 /2 (11.4) 81/4 (15.0) 9 (16.3)
1

67/8 (6.2) 67/8 (6.2) 7 (9.3) 71/4 (9.7) 7 (12.7) 73/4 (14.1) 7 (16.2) 8 (18.5) 8 (18.5) 97/8 (22.8) 11 9? 16 (26.7) 12 15? 16 (29.9) 151/2 (35.6) 173/8 (40.1) 173/8 (40.1) 6.3 Designation

55/8 (5.1) 55/8 (5.1) 53/4 (7.7) 6 (8.0) 53/4 (10.4) 61/2 (11.7) 53/4 (13.3) 63/4 (15.6) 63/4 (15.6) 85/8 (19.9) 10 1? 16 (23.2) 11 7? 16 (26.4) 14 (32.3) 157/8 (36.6) 157/8 (36.6)

3

/8

1

/2

3

/4

1 11/4 11/2 2 21/2 3 4 5 6
NOTE

81/4 (19.0) 91/4 (21.4) 91/4 (21.4) 111/8 (25.7) 13 1? 16 (30.1) 14 7? 16 (33.3) 17 (39.3) 187/8 (43.6) 187/8 (43.6)

Linear values are given in parentheses and are rounded to 0.1 mm.

6.2 Dimensions and tolerances The basic diameters of the longscrew threads shall be as given in columns 5, 6 and 7 of Table 2. The parallel external threads on the longscrews shall be of such size that the socket and backnut (threaded in accordance with the requirements of 5.3.1) will run on the longscrew hand-tight without perceptible shake (see note).
NOTE It is not possible to lay down any practicable tolerances for the threads of such longscrews and it is necessary therefore to select the components for assembly. To ensure this requirement being met, the selected components should always be used together.

Longscrew threads shall be designated by the letters RL, together with the thread size. These screw threads shall be referred to on drawings and related documents in the following manner: RL?

6

? BSI 03-1999

BS 21:1985

NOTE 1 NOTE 2 NOTE 3 NOTE 4

It is the parallel thread which is illustrated in (c) and (d). The taper of the gauge is shown exaggerated in the diagrams. Values of T1/2 are given in column 9 of Table 2, values of T2/2 are given in column 17 of Table 2. The taper screw plug gauges are used in a similar manner for gauging internal taper threads.

Figure 5 — System A screw gauges assembled respectively with threads of maximum and minimum sizes

? BSI 03-1999

7

BS 21:1985

NOTE 1 It is the parallel thread which is illustrated in (c) and (d). NOTE 2 The taper of the gauge is shown exaggerated in the diagram. NOTE 3 The taper plain plug and plain ring gauges are used in a similar manner to that illustrated for screw plug and ring gauges. NOTE 4 The taper screw plug gauges are used in a similar manner for gauging internal taper threads.

Figure 6 — System B screw gauges assembled respectively with threads of maximum and minimum sizes

8

? BSI 03-1999

Table 2 — Basic dimensions and limits of size

? BSI 03-1999

BS 21:1985

9

BS 21:1985

Appendix A Recommended gauging systems for jointing threads
A.1 General This appendix gives details of alternative systems of gauging recommended for use in the control of threads intended to comply with the requirements of this standard for jointing threads. Elaborate methods of inspection are not regarded as necessary or even practicable. It is considered that under appropriate conditions, gauging by either of the recommended systems, coupled with visual inspection, will suffice to ensure satisfactory products having threads which will make sound joints and which will comply with this standard. The use of either recommended system is not specified and the recommendations are given only for guidance. System A is intended for use where additional production control methods are employed to ensure the general accuracy of the threads. System B is intended for use where the adequacy of production control is not otherwise established. The taper plug gauges in systems A and B may be used for gauging both taper and parallel internal pipe threads. A.2 System A A.2.1 Description of gauges System A comprises the following types of gauges. a) A taper full-form screw plug gauge (see Figure 7). This gauge has a step at the gauge plane; the length of the thread from the gauge plane step to the small end of the plug is equal to the basic gauge length. The length of the thread from this gauge plane step to the large end is approximately 3 pitches.

b) A taper full-form screw ring gauge (see Figure 8). This gauge has a length of thread equal to the basic gauge length and the large end diameters are equal to the basic diameters at the gauge plane.

NOTE

See Table 3 for dimensions.

Figure 8 — Taper full-form screw ring gauge (system A) A.2.2 Dimensions and tolerances The dimensions for gauges in system A are given in Table 3 and the tolerances for gauges are given in Table 5. A.3 System B A.3.1 Description of gauges System B comprises the following types of gauges. a) A taper full-form screw plug gauge (see Figure 9). This gauge has a total length of thread equal to the length of useful thread for maximum gauge length, and incorporates a step equal to the total tolerance on the position of the gauge plane. The upper face of the step is marked positive (+) and the lower face is marked negative (–).
NOTE Because of the necessity to remove incomplete threads, it is recommended that the taper full-form screw plug gauges be extended at the large diameter end by an amount equal to three pitches beyond the gauge plane. This will require an additional step to indicate useful thread length at maximum gauge length, marked positive (+).

NOTE

See Table 3 for dimensions.

Figure 7 — Taper full-form screw plug gauge (system A)

10

? BSI 03-1999

BS 21:1985

Table 3 — Dimensions of taper full-form screw plug and ring gauges for system A
1 Thread size designation 2 3 Basic diameters at gauge plane Major Pitch Minor 4 5 6 7 Taper screw ring gauge Overall length of gauge, a mm Taper screw plug gauge Small end of plug to gauge plane step, a mm Overall length of thread, b mm

mm /8 1 /4
3 /8 1/ 2 3/ 4 1
1? 16

mm

mm

7.723 9.728 13.157 16.662 20.955 26.441 33.249 41.910 47.803 59.614 75.184 87.884 113.030 138.430 163.830

7.142 9.147 12.301 15.806 19.793 25.279 31.770 40.431 46.324 58.135 73.705 86.405 111.551 136.951 162.351

6.561 8.566 11.445 14.950 18.631 24.117 30.291 38.952 44.845 56.656 72.226 84.926 110.072 135.472 160.872

4.0 4.0 6.0 6.4 8.2 9.5 10.4 12.7 12.7 15.9 17.5 20.6 25.4 28.6 28.6

6.6 6.6 9.9 10.4 13.7 15.0 17.3 19.6 19.6 22.9 24.4 27.7 32.3 35.6 35.6

4.0 4.0 6.0 6.4 8.2 9.5 10.4 12.7 12.7 15.9 17.5 20.6 25.4 28.6 28.6

1 11/4 11/2 2 21/2 3 4 5 6
NOTE 1 NOTE 2

For gauge tolerances, see Table 5. For illustration of gauges, see Figure 7 and Figure 8. The taper is 1 in 16 measured on diameter.

b) A taper full-form screw ring gauge (see Figure 10). This gauge has a total length of thread equal to the length of useful thread for maximum gauge length minus half the wrenching allowance, and incorporates a step equal to the total tolerance on the gauge length. The upper face of the step is marked positive (+) and the lower face is marked negative (–). c) A taper plain plug gauge (see Figure 11). This gauge has an overall length equal to the fitting allowance plus 0.75 times the total tolerance on the position of the gauge plane, and incorporates a step equal to 1.25 times the total tolerance on the position of the gauge plane. The distance k from the gauge plane to the upper face of the step is equal to 1.5 times the positive tolerance on the internal thread (column 17 of Table 2). The upper face of the step is marked positive (+) and the lower face is marked negative (–), but this marking may be omitted where space does not allow for it. The gauge will accept internal threads having small errors of taper and thread depth.

d) A taper plain ring gauge (see Figure 12). This gauge has an overall length equal to the length of useful thread for maximum gauge length minus half the wrenching allowance. It incorporates a step at the small end of the taper equal to 1.25 times the total tolerance on the gauge length and having the upper face marked positive (+) and the lower face marked negative (–). The distance m from the gauge plane to the upper face of the step is equal to the minimum gauge length plus the height of the step. The gauge is recessed at the small end to a distance representing the negative (–) tolerance for an internal thread measured from the gauge plane. This gauge will accept external threads having small errors of taper and thread depth. A.3.2 Dimensions and tolerances The dimensions for gauges in system B are given in Table 4 and the tolerances for gauges are given in Table 5.

? BSI 03-1999

11

BS 21:1985

NOTE

See Table 4 for dimensions.

NOTE

See Table 4 for dimensions.

Figure 9 — Taper full-form screw plug gauge (system B)

Figure 11 — Taper plain plug gauge (system B)

NOTE

See Table 4 for dimensions.

NOTE

See Table 4 for dimensions.

Figure 10 — Taper full-form screw ring gauge (system B)

Figure 12 — Taper plain ring gauge (system B)

12

? BSI 03-1999

Table 4 — Dimensions of taper full-form screw and taper plain plug and ring gauges for system B
1 Thread size designation 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Basic diameters at gauge plane Major Pitch Minor Taper screw plug gauge Taper screw ring gauge Taper plain plug gauge (see note 3) Taper plain ring gauge (see note 4)

? BSI 03-1999

Overall Gauge Depth Overall Gauge Depth Overall Gauge Depth Overall Gauge Depth Depth of plane of step, length plane to of step, length, plane to of step, length, plane to of step, counterlength + face + face + face of to + of bore, G n l f t j e face datum, datum, k thread, f datum, g thread, datum, m c s mm mm mm mm mm mm mm mm mm mm mm mm mm

mm
1? 16

mm

mm

7.723 9.728 13.157 16.662 20.955 26.441 33.249 41.910 47.803 59.614 75.184 87.884

7.142 9.147 12.301 15.806 19.793 25.279 31.770 40.431 46.324 58.135 73.705 86.405

6.561 8.566

7.4 7.4

1.1 1.1 1.7 1.7 2.3 2.3 2.9 2.9 2.9 2.9 3.5 3.5 3.5 3.5 3.5

2.2 2.2 3.4 3.4 4.6 4.6 5.8 5.8 5.8 5.8 7.0 7.0 7.0 7.0 7.0

6.7 6.7 10.0 10.4 13.6 15.0 17.3 19.6 19.6 23.4 27.3 30.4 35.8 39.5 39.5

4.9 4.9 7.3 7.7 10.0 11.3 12.7 15.0 15.0 18.2 21.0 24.1 28.9 32.1 32.1

1.8 1.8 2.6 2.6 3.6 3.6 4.6 4.6 4.6 4.6 7.0 7.0 7.0 7.0 7.0

4.2 4.2 6.2 6.2 8.4 8.4 10.7 10.7 10.7 11.8 14.4 14.4 15.6 16.7 16.7

1.6 1.6 2.5 2.5 3.4 3.4 4.3 4.3 4.3 4.3 5.2 5.2 5.2 5.2 5.2

2.8 2.8 4.2 4.2 5.7 5.7 7.2 7.2 7.2 7.2 8.7 8.7 8.7 8.7 8.7

6.7 6.7 10.0 10.4 13.6 15.0 17.3 19.6 19.6 23.4 27.3 30.4 35.8 39.5 39.5

5.3 5.3 8.0 8.4 10.9 12.2 13.8 16.2 16.2 19.3 22.7 25.8 30.6 33.8 33.8

2.2 2.2 3.2 3.2 4.5 4.5 5.8 5.8 5.8 5.8 8.7 8.7 8.7 8.7 8.7

4.2 4.2 6.3 6.7 8.6 9.9 10.9 13.3 13.3 16.4 19.2 22.3 27.1 30.3 30.3

1 1

/8 /4

11.445 11.0 14.950 11.4 18.631 15.0 24.117 16.3 30.291 19.1 38.952 21.4 44.845 21.4 56.656 25.7 72.226 30.2 84.926 33.3

3/ 8 1/ 2 3/ 4

1 11/ 1 2 21/2 3 4 5 6
1 4

/2

113.030 111.551 110.072 39.3 138.430 136.951 135.472 43.6 163.830 162.351 160.872 43.6

NOTE 1 For gauge tolerances, see Table 5. For illustration of gauges, see Figure 9, Figure 10, Figure 11, Figure 12. NOTE 2 The taper is 1 in 16 measured on diameter. NOTE 3 Taper plain plug gauge: the basic diameter at the gauge plane is the basic minor diameter of the screw thread (see column 4). NOTE 4 Taper plain ring gauge: the basic diameter at the gauge plane is the basic major diameter of the screw thread (see column 2).

BS 21:1985

13

Table 5 — Manufacturing tolerances for gauges for systems A and B

14
? BSI 03-1999

BS 21:1985

BS 21:1985

Appendix B Methods of verification of jointing thread dimensions and form using recommended gauging systems described in Appendix A
B.1 System A B.1.1 Gauging taper external pipe threads Screw the taper full-form screw ring gauge (see Figure 8) hand-tight on to the external thread. B.1.2 Gauging taper or parallel internal pipe threads Screw the taper full-form screw plug gauge (see Figure 7) hand-tight into the internal thread. B.2 System B B.2.1 Gauging taper external pipe threads B.2.1.1 Screw the taper full-form screw ring gauge (see Figure 10) hand-tight on to the external thread. B.2.1.2 Assemble the taper plain ring gauge (see Figure 12) by hand with the external threads, taking care not to use an excessive amount of force. B.2.2 Gauging taper or parallel internal pipe threads B.2.2.1 Screw the taper full-form screw plug gauge (see Figure 9) hand-tight into the internal thread. B.2.2.2 Assemble the taper plain plug gauge (see Figure 11) by hand with the internal thread, taking care not to use an excessive amount of force.

Appendix C Special parallel external threads for gas appliances where pressure-tight seals are made on machined faces
C.1 General
NOTE Parallel internal threads for use with special parallel external threads for gas appliance applications should accept a parallel length of threaded pipe-end in accordance with those lengths given in column 13 of Table 2.

Except when used for stud ends, there shall be at least five threads engagement. The length of threads on stud ends shall comply with the appropriate British Standard. C.2 Dimensions and tolerances Dimensions and tolerances for special parallel external threads shall be as given in Table 6. C.3 Designation Special parallel external threads for gas appliances where pressure-tight seals are made on machined faces shall be designated by the letters RS, together with the thread size. These screw threads shall be referred to on drawings and related documents in the following manner: RS ?

? BSI 03-1999

15

Table 6 — Special parallel external threads for gas appliances where pressure-tight seals are made on machined faces
1 2 3 4 5 6 7 8 9 10 11 12 13 14 Minor diameter Basic mm Tolerance Maximum mm mm 15 Thread size Number of designation threads in 25.4 mm Pitch, Depth of P thread mm
1

16
/8
1

BS 21:1985

Major diameter (gauge diameter) Basic mm Tolerance Maximum Minimum mm mm mm Basic mm

Pitch diameter Tolerance Maximum Minimum mm mm mm

mm

28 19 19 14 14 11 11 11 11

0.907 1.337 1.337 1.814 1.814 2.309 2.309 2.309 2.309

0.581 0.856 0.856 1.162 1.162 1.479 1.479 1.479 1.479

9.728 – 0.089 – 0.284 13.157 – 0.124 – 0.353 16.662 – 0.124 – 0.353 20.955 – 0.168 – 0.427 26.441 – 0.168 – 0.427 33.249 – 0.211 – 0.541 41.910 – 0.211 – 0.541 47.803 – 0.211 – 0.541 59.614 – 0.211 – 0.541

9.639 13.033 16.538 20.787 26.273 33.038 41.699 47.592 59.403

9.444 12.804 16.309 20.528 26.014 32.708 41.369 47.262 59.073

9.147 – 0.089 – 0.196 12.301 – 0.124 – 0.249 15.806 – 0.124 – 0.249 19.793 – 0.168 – 0.310 25.279 – 0.168 – 0.310 31.770 – 0.211 – 0.391 40.431 – 0.211 – 0.391 46.324 – 0.211 – 0.391 58.135 – 0.211 – 0.391

9.058 12.177 15.682 19.625 25.11 31.559 40.221 46.113 57.924

8.951 12.052 15.557 19.483 24.969 31.379 40.040 45.933 57.744

8.566 – 0.089 and over 11.445 – 0.124 and over 14.950 – 0.124 and over 18.631 – 0.168 and over 24.117 – 0.168 and over 30.291 – 0.211 and over 38.952 – 0.211 and over 44.845 – 0.211 and over 56.656 – 0.211 and over

8.477 11.321 14.826 18.463 23.949 30.080 38.741 44.634 56.445

/4

3

/8

1

/2

3

/4

1 11/4 11/ 2
NOTE

2

For the gauging of these threads, reference may be made to BS 919-2.

? BSI 03-1999

BS 21:1985

Publications referred to
BS 919, Screw gauge limits and tolerances. BS 919-2, Gauges for screw threads of Whitworth and BA forms. BS 1387, Steel tubes and tubulars suitable for screwing to BS 21 pipe threads. BS 2779, Pipe threads where pressure-tight joints are not made on the threads. ISO 7, Pipe threads where pressure-tight joints are made on the threads1). ISO 7-1, Designation, dimensions and tolerances. ISO 7-2, Verification by means of limit gauges.

1) Referred

to in the foreword only.

? BSI 03-1999

BS 21:1985

BSI — British Standards Institution
BSI is the independent national body responsible for preparing British Standards. It presents the UK view on standards in Europe and at the international level. It is incorporated by Royal Charter. Revisions British Standards are updated by amendment or revision. Users of British Standards should make sure that they possess the latest amendments or editions. It is the constant aim of BSI to improve the quality of our products and services. We would be grateful if anyone finding an inaccuracy or ambiguity while using this British Standard would inform the Secretary of the technical committee responsible, the identity of which can be found on the inside front cover. Tel: 020 8996 9000. Fax: 020 8996 7400. BSI offers members an individual updating service called PLUS which ensures that subscribers automatically receive the latest editions of standards. Buying standards Orders for all BSI, international and foreign standards publications should be addressed to Customer Services. Tel: 020 8996 9001. Fax: 020 8996 7001. In response to orders for international standards, it is BSI policy to supply the BSI implementation of those that have been published as British Standards, unless otherwise requested. Information on standards BSI provides a wide range of information on national, European and international standards through its Library and its Technical Help to Exporters Service. Various BSI electronic information services are also available which give details on all its products and services. Contact the Information Centre. Tel: 020 8996 7111. Fax: 020 8996 7048. Subscribing members of BSI are kept up to date with standards developments and receive substantial discounts on the purchase price of standards. For details of these and other benefits contact Membership Administration. Tel: 020 8996 7002. Fax: 020 8996 7001. Copyright Copyright subsists in all BSI publications. BSI also holds the copyright, in the UK, of the publications of the internationalstandardization bodies. Except as permitted under the Copyright, Designs and Patents Act 1988 no extract may be reproduced, stored in a retrieval system or transmitted in any form or by any means – electronic, photocopying, recording or otherwise – without prior written permission from BSI. This does not preclude the free use, in the course of implementing the standard, of necessary details such as symbols, and size, type or grade designations. If these details are to be used for any other purpose than implementation then the prior written permission of BSI must be obtained. If permission is granted, the terms may include royalty payments or a licensing agreement. Details and advice can be obtained from the Copyright Manager. Tel: 020 8996 7070.

BSI 389 Chiswick High Road London W4 4AL


相关文章:
螺纹各国标准对照
1:16 的锥度,相当于国内的 55 度圆锥管螺纹,即 ...公制螺纹与英制螺纹的区别: 公制螺纹用螺距来表示,...提出英国惠氏螺纹,1905 年,颁布惠氏螺纹新标准(BS ...
英制公制管螺纹对照表
英制公制管螺纹对照表_信息与通信_工程科技_专业资料。英制,公制螺纹对照表. ...2页 1下载券 英制螺纹规格公制螺纹... 2页 免费 公制 英制 美制螺纹对照...
管螺纹标准
公制螺纹公制单位, 美英制螺纹用英制单位。管螺纹...1/4 , 1/2 , 1/8 是英制螺纹的公称直径,单位...惠氏螺纹, 1905 年,颁布惠氏螺纹新标准( BS 84 )...
公制螺纹标准手册
公制螺纹标准手册_工程科技_专业资料。公制螺纹标准 ...英国 BS BS ISO 68-1 :1998 BS 3643-1 :2007...2. 美国的米制普通螺纹标准有两套,分别由机械工程...
管螺纹标准
公制螺纹公制单位, 美英制螺纹用英制 单位。管...1/4 , 1/2 , 1/8 是英制螺纹的公称直径,单位...惠氏螺纹, 1905 年,颁布惠氏螺纹标准( BS 84 )...
管螺纹标准
螺纹尺寸,英寸等于 8 分,1/4 英寸就是 2 分...公制螺纹公制单位, 美英制螺纹用英制单位。管螺纹...提出英国惠氏螺纹,1905 年,颁布惠氏螺纹新标准(BS ...
英制螺纹标准对照表
英制螺纹标准对照表_机械/仪表_工程科技_专业资料。英制,公制螺纹对照表. 尺寸代号 (in) 1/16 1/8 1/4 3/8 1/2 5/8 3/4 7/8 1 1-1/8 1-1/4...
公制螺纹标准
(一) 圆柱螺纹 1. 普通螺纹(又称米制或公制螺纹...第次工业革命后,英国人发明了车床、板牙和丝锥,...提出了世界上第螺纹国家标准 (BS 84,惠氏螺纹...
最新GB公制螺纹标准
(一) 圆柱螺纹 1. 普通螺纹(又称米制或公制螺纹...第次工业革命后,英国人发明了车床、板牙和丝锥,...(BS 84,惠氏螺纹,B.S.W 和 B.S.F),从而奠定...
公制螺纹标准
1) 4,3,2,1.5,(1) 4,3,2,1.5,(1) 螺纹...第次工业革命后,英国人发明了车床、板牙和丝锥,...提出了世 界上第螺纹国家标准(BS 84,惠氏螺纹...
更多相关标签:
公制螺纹标准 | 公制螺纹标准对照表 | 公制螺纹标准手册 | 标准公制螺纹规格表 | 公制细牙螺纹标准 | 公制外螺纹标准 | 公制管螺纹标准 | 国际公制标准螺纹 |