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BS 84:2007

BS 84:2007

$198.66

Parallel screw threads of Whitworth form. Requirements

Published By Publication Date Number of Pages
BSI 2007 66
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This British Standard specifies limits of sizes, and tolerances, for single start parallel screw threads of Whitworth form, for general engineering use. It is not applicable to threads for threaded pipe joints, screw threads associated with interference fits, such as those on the “metal ends” of studs and in the corresponding tapped holes, or to screw threads which are to be subjected to high temperatures.

This standard specifies the following thread series:

  1. a coarse thread series, the British Standard Whitworth (B.S.W.) series, with nominal diameters in the range in to 6 in.

  2. a fine thread series, the British Standard fine (B.S.F.) series, with nominal diameters in the range in to in.

    NOTE The tables of limits and tolerances for the B.S.F. series extend up to the 3 in size only, since nominal sizes above 3 in are rarely used.

  3. a supplementary selected thread (WHIT. S.) series with nominal diameters from in to 7 in.

  4. a truncated Whitworth form series (specified in Annex A).

This British Standard specifies limits of sizes, and tolerances, of uncoated threads and also for metal coated threads (including threads coated with nickel, tin or zinc) with a thickness of coating of the order of 0.000 2 in. It is not applicable to heavily coated threads (i.e. threads with a coating thickness above 0.000 35 in).

NOTE Supplementary information is given in Annex B, Annex C and Annex D.

PDF Catalog

PDF Pages PDF Title
3 Contents
1 Scope 1
2 Normative references 1
3 Terms and definitions and symbols 1
4 Profile of Whitworth screw thread 2
5 Tolerance classes of external and internal threads 3
6 Limits of sizes, and tolerances, for uncoated B.S.W. and B.S.F. threads 3
7 Limits of size, and tolerances, for B.S.W. and B.S.F. coated threads 4
8 Stainless steel external threads 5
9 Selected thread series 6
10 Designation of screw threads of Whitworth form 8
11 Gauges 8
Annexes
Annex A (normative) Truncated Whitworth form threads with flat crests 40
Annex B (informative) Bases of tolerances and allowances for Whitworth form screw threads 47
Annex C (informative) Tolerances on pitch and flank angle in relation to tolerance on effective diameter 50
Annex D (informative) Form of the crests of Whitworth threads 53
Annex E (normative) Limits and tolerances for close class internal threads for special uses 55
List of figures
Figure 1 – Basic form of Whitworth thread 9
Figure 2 – Effective diameter tolerance zones of recommended combinations of classes of internal and external Whitworth form threads 10
Figure 3 – Tolerance zones for a close class external thread and a medium class internal thread [ in B.S.W. (20 t.p.i.) illustrated] 11
Figure 4 – Tolerance zones for a medium class external thread with allowance and a normal class internal thread [ in B.S.W. (20 t.p.i.) illustrated] 12
Figure 5 – Tolerance zones for a free class external thread with allowance and a normal class internal thread [ in B.S.W. (20 t.p.i.) illustrated] 13
Figure 6 – Effective diameter tolerance zones for external and internal threads, uncoated or before coating, and after coating (c.f. Figure 2) of sizes in nominal size and smaller 14
Figure A.1 – Tolerance zones for truncated Whitworth threads (close class external thread and medium class internal thread) [ in B.S.W. (20 t.p.i.) illustrated] 43
Figure D.1 – Crest forms resulting from different production methods 54
List of tables
Table 1 – Coarse thread series (B.S.W.) – Basic sizes 15
Table 2 – Coarse thread series (B.S.W.) – External threads – Close class – Limits and tolerances 16
4 Table 3 – Coarse thread series (B.S.W.) – Internal threads – Medium class – Limits and tolerances 17
Table 4 – Coarse thread series (B.S.W.) – External threads – Medium class – Limits and tolerances 18
Table 5 – Coarse thread series (B.S.W.) – Internal threads – Normal class – Limits and tolerances 19
Table 6 – Coarse thread series (B.S.W.) – External threads – Free class – Limits and tolerances 20
Table 7 – Fine thread series (B.S.F.) – Basic sizes 21
Table 8 – Fine thread series (B.S.F.) – External threads – Close class – Limits and tolerances 22
Table 9 – Fine thread series (B.S.F.) – Internal threads – Medium class – Limits and tolerances 23
Table 10 – Fine thread series (B.S.F.) – External threads – Medium class – Limits and tolerances 24
Table 11 – Fine thread series (B.S.F.) – Internal threads – Normal class – Limits and tolerances 25
Table 12 – Fine thread series (B.S.F.) – External threads – Free class – Limits and tolerances 26
Table 13A – Selected thread series (Whit. S.) – Preferred diameters and pitches – Fractional sizes 27
Table 13B – Selected thread series (Whit. S.) – Preferred diameters and pitches – Decimal sizes 31
Table 14 – Selected thread series (Whit. S.) and non-standard threads – Depths of thread for various pitches 34
Table 15 – Selected thread series (Whit. S.) and non-standard threads – External threads – Medium and free class – Allowances 37
Table 16 – Selected thread series (Whit. S.) and non-standard threads – External threads – Close class – Tolerances 37
Table 17 – Selected thread series (Whit. S.) and non-standard threads – Internal threads – Medium class – Tolerances 38
Table 18 – Selected thread series (Whit. S.) and non-standard threads – External threads – Medium class – Tolerances 38
Table 19 – Selected thread series (Whit. S.) and non-standard threads – Internal threads – Normal class – Tolerances 39
Table 20 – Selected thread series (Whit. S.) and non-standard threads – External threads – Free class – Tolerances 39
Table A.1 – Truncated threads – Whitworth form – Basic data 44
Table A.2 – Truncated threads – British Standard Whitworth (B.S.W.) series – External and internal threads – All classes – Limits and tolerances 45
Table A.3 – Truncated threads – British Standard Fine (B.S.F.) series – External and internal threads – All classes – Limits and tolerances 46
Table E.1 – Coarse thread series (B.S.W.) – Internal threads – Close class – Limits and tolerances 55
Table E.2 – Fine thread series (B.S.F.) – Internal threads – Close class – Limits and tolerances 56
Table E.3 – Selected and non-standard threads – Internal threads – Close class – Tolerances 57
5 Foreword
7 1 Scope
a) a coarse thread series, the British Standard Whitworth (B.S.W.) series, with nominal diameters in the range in to 6 in.
b) a fine thread series, the British Standard fine (B.S.F.) series, with nominal diameters in the range in to 4 in.
c) a supplementary selected thread (WHIT. S.) series with nominal diameters from in to 7 in.
d) a truncated Whitworth form series (specified in Annex A).
2 Normative references
3 Terms and definitions and symbols
3.1 Terms and definitions
8 3.2 Symbols
4 Profile of Whitworth screw thread
9 5 Tolerance classes of external and internal threads
a) close class external threads;
b) medium class external threads and internal threads;
c) free class external threads;
d) normal class internal threads.
6 Limits of sizes, and tolerances, for uncoated B.S.W. and B.S.F. threads
10 7 Limits of size, and tolerances, for B.S.W. and B.S.F. coated threads
11 8 Stainless steel external threads
12 9 Selected thread series
9.1 General
9.2 Basic sizes
9.3 Design sizes
9.3.1 Internal threads
9.3.2 External threads
a) Close class. The design sizes shall be the same as the basic sizes.
b) Medium class and free class:
2) Basic major diameters above in. The design sizes shall be the same as the basic sizes.
13 9.4 Tolerances
14 10 Designation of screw threads of Whitworth form
11 Gauges
15 Figure 1 Basic form of Whitworth thread
16 Figure 2 Effective diameter tolerance zones of recommended combinations of classes of internal and external Whitworth form threads
17 Figure 3 Tolerance zones for a close class external thread and a medium class internal thread [ in B.S.W. (20 t.p.i.) illustrated]
18 Figure 4 Tolerance zones for a medium class external thread with allowance and a normal class internal thread [ in B.S.W. (20 t.p.i.) illustrated]
19 Figure 5 Tolerance zones for a free class external thread with allowance and a normal class internal thread [ in B.S.W. (20 t.p.i.) illustrated]
20 Figure 6 Effective diameter tolerance zones for external and internal threads, uncoated or before coating, and after coating (c.f. Figure 2) of sizes in nominal size and smaller
21 Table 1 Coarse thread series (B.S.W.) – Basic sizes
22 Table 2 Coarse thread series (B.S.W.) – External threads – Close class – Limits and tolerances
23 Table 3 Coarse thread series (B.S.W.) – Internal threads – Medium class – Limits and tolerances
24 Table 4 Coarse thread series (B.S.W.) – External threads – Medium class – Limits and tolerances
25 Table 5 Coarse thread series (B.S.W.) – Internal threads – Normal class – Limits and tolerances
26 Table 6 Coarse thread series (B.S.W.) – External threads – Free class – Limits and tolerances
27 Table 7 Fine thread series (B.S.F.) – Basic sizes
28 Table 8 Fine thread series (B.S.F.) – External threads – Close class – Limits and tolerances
29 Table 9 Fine thread series (B.S.F.) – Internal threads – Medium class – Limits and tolerances
30 Table 10 Fine thread series (B.S.F.) – External threads – Medium class – Limits and tolerances
31 Table 11 Fine thread series (B.S.F.) – Internal threads – Normal class – Limits and tolerances
32 Table 12 Fine thread series (B.S.F.) – External threads – Free class – Limits and tolerances
33 Table 13A Selected thread series (Whit. S.) – Preferred diameters and pitches – Fractional sizes
34 Table 13A Selected thread series (Whit. S.) – Preferred diameters and pitches – Fractional sizes (continued)
35 Table 13A Selected thread series (Whit. S.) – Preferred diameters and pitches – Fractional sizes (continued)
36 a) up to and including 1 in: the nearest in size;
b) above 1 in up to and including 6 in: the nearest in size;
c) above 6 in: the nearest in size.
37 Table 13B Selected thread series (Whit. S.) – Preferred diameters and pitches – Decimal sizes
38 Table 13B Selected thread series (Whit. S.) – Preferred diameters and pitches – Decimal sizes (continued)
39 a) up to and including 1.5 in: the nearest 0.030 in size;
b) above 1.5 in up to and including 6 in: the nearest 0.060 in size;
c) above 6 in: the nearest 0.125 in size.
40 Table 14 Selected thread series (Whit. S.) and non-standard threads – Depths of thread for various pitches
43 Table 15 Selected thread series (Whit. S.) and non-standard threads – External threads – Medium and free class – Allowances
Table 16 Selected thread series (Whit. S.) and non-standard threads – External threads – Close class – Tolerances
44 Table 17 Selected thread series (Whit. S.) and non-standard threads – Internal threads – Medium class – Tolerances
Table 18 Selected thread series (Whit. S.) and non-standard threads – External threads – Medium class – Tolerances
45 Table 19 Selected thread series (Whit. S.) and non-standard threads – Internal threads – Normal class – Tolerances
Table 20 Selected thread series (Whit. S.) and non-standard threads – External threads – Free class – Tolerances
46 Annex A (normative) Truncated Whitworth form threads with flat crests
A.1 Profile of truncated Whitworth threads
A.2 Limits and tolerances
A.2.1 General
47 A.2.2 Limits and tolerances on the major diameter of external threads and the minor diameter of internal threads
48 A.3 Designation
A.4 Gauging system
a) for external threads:
1) GO screw ring or calliper gauge;
2) NOT GO effective diameter calliper gauge;
3) GO plain calliper gauge for flat crests;
4) NOT GO plain calliper gauge for flat crests;
b) for internal threads:
1) GO screw plug gauge;
2) NOT GO effective diameter plug gauge;
3) GO plain plug gauge for flat crests;
4) NOT GO plain plug gauge for flat crests.
49 Figure A.1 Tolerance zones for truncated Whitworth threads (close class external thread and medium class internal thread) [ in B.S.W. (20 t.p.i.) illustrated]
50 Table A.1 Truncated threads – Whitworth form – Basic data
51 Table A.2 Truncated threads – British Standard Whitworth (B.S.W.) series – External and internal threads – All classes – Limits and tolerances
52 Table A.3 Truncated threads – British Standard Fine (B.S.F.) series – External and internal threads – All classes – Limits and tolerances
53 Annex B (informative) Bases of tolerances and allowances for Whitworth form screw threads
B.1 General
B.2 Tolerance classes
B.3 Allowances
B.4 Tolerances on effective diameter
54 B.5 Tolerances on major diameter
B.5.1 External threads
B.5.2 Internal threads
55 B.6 Tolerances on minor diameter
B.6.1 External threads
B.6.2 Internal threads
B.7 Minimum depths of engagement
56 Annex C (informative) Tolerances on pitch and flank angle in relation to tolerance on effective diameter
C.1 Effect of pitch errors
C.2 Effects of errors in flank angle
57 C.3 Criteria for acceptability of a combination of errors in the effective diameter, pitch and flank angle of a screw thread
a) External threads. The simple effective diameter of an external thread (as measured along the pitch line of the thread) should…
b) Internal threads. The simple effective diameter of an internal thread (as measured along the pitch line) should lie between t…
59 Annex D (informative) Form of the crests of Whitworth threads
D.1 General
D.2 Internal threads
D.3 External threads
60 Figure D.1 Crest forms resulting from different production methods
61 Annex E (normative) Limits and tolerances for close class internal threads for special uses
Table E.1 Coarse thread series (B.S.W.) – Internal threads – Close class – Limits and tolerances
62 Table E.2 Fine thread series (B.S.F.) – Internal threads – Close class – Limits and tolerances
63 Table E.3 Selected and non-standard threads – Internal threads – Close class – Tolerances
64 Bibliography

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BS 84:2007
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