Threads and Threading - Sportpilot.info
Threads and Threading - Sportpilot.info
Threads and Threading - Sportpilot.info
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1870 BRITISH PIPE THREADS<br />
For external threads two classes of tolerance are provided <strong>and</strong> for internal, one class. The<br />
two classes of tolerance for external threads are Class A <strong>and</strong> Class B. For economy of manufacture<br />
the class B fit should be chosen whenever possible. The class A is reserved for<br />
those applications where the closer tolerance is essential. Class A tolerance is an entirely<br />
negative value, equivalent to the internal thread tolerance. Class B tolerance is an entirely<br />
negative value twice that of class A tolerance. Tables showing limits <strong>and</strong> dimensions are<br />
given in the St<strong>and</strong>ard.<br />
The thread series specified in this St<strong>and</strong>ard shall be designated by the letter “G”. A typical<br />
reference on a drawing might be “G 1 ⁄ 2 ”, for internal thread; “G 1 ⁄ 2 A”, for external thread,<br />
class A: <strong>and</strong> “G 1 ⁄ 2 B”, for external thread, class B. Where no class reference is stated for<br />
external threads, that of class B will be assumed. The designation of truncated threads shall<br />
have the addition of the letter “T” to the designation, i.e., G 1 ⁄ 2 T <strong>and</strong> G 1 ⁄ 2 BT.<br />
Nominal<br />
Size, Inches<br />
<strong>Threads</strong><br />
per Inch a<br />
1 ⁄16 28 {<br />
1 ⁄8 28 {<br />
1 ⁄4 19 {<br />
3 ⁄8 19 {<br />
1 ⁄2 14 {<br />
5 ⁄8 14 {<br />
3 ⁄4 14 {<br />
7 ⁄8 14 {<br />
1 11 {<br />
1 1 ⁄ 8 11 {<br />
1 1 ⁄ 4 11 {<br />
1 1 ⁄ 2 11 {<br />
British St<strong>and</strong>ard Pipe <strong>Threads</strong> (Non-pressure-tight Joints)<br />
Metric <strong>and</strong> Inch Basic Sizes BS 2779:1973<br />
Depth of<br />
Thread<br />
Major<br />
Diameter<br />
Machinery's H<strong>and</strong>book 27th Edition<br />
Pitch<br />
Diameter<br />
Minor<br />
Diameter<br />
a The thread pitches in millimeters are as follows: 0.907 for 28 threads per inch. 1.337 for 19 threads<br />
per inch, 1.814 for 14 threads per inch, <strong>and</strong> 2.309 for 11 threads per inch.<br />
Each basic metric dimension is given in roman figures (nominal sizes excepted) <strong>and</strong> each basic<br />
inch dimension is shown in italics directly beneath it.<br />
British St<strong>and</strong>ard Pipe <strong>Threads</strong> for Pressure-tight Joints.—The threads in BS<br />
21:1973, “Specification for Pipe <strong>Threads</strong> where Pressure-tight Joints are Made on the<br />
<strong>Threads</strong>”, are based on the Whitworth thread form <strong>and</strong> are specified as:<br />
1) Jointing threads: These relate to pipe threads for joints made pressure-tight by the<br />
mating of the threads; they include taper external threads for assembly with either taper or<br />
parallel internal threads (parallel external pipe threads are not suitable as jointing threads)<br />
2) Longscrew threads: These relate to parallel external pipe threads used for longscrews<br />
(connectors) specified in BS 1387 where a pressure-tight joint is achieved by the compression<br />
of a soft material onto the surface of the external thread by tightening a back nut<br />
against a socket<br />
Nominal<br />
Size, Inches<br />
<strong>Threads</strong><br />
per Inch a<br />
Depth of<br />
Thread<br />
Major<br />
Diameter<br />
Pitch<br />
Diameter<br />
Minor<br />
Diameter<br />
0.581 7.723 7.142 6.561<br />
13 0.0229 0.3041 0.2812 0.2583<br />
⁄ 4<br />
11<br />
{<br />
1.479<br />
0.0582<br />
53.746<br />
2.1160<br />
52.267<br />
2.0578<br />
50.788<br />
1.9996<br />
0.581<br />
0.0229<br />
9.728<br />
0.3830<br />
9.147<br />
0.3601<br />
8.566<br />
0.3372<br />
2 11 {<br />
1.479<br />
0.0582<br />
59.614<br />
2.3470<br />
58.135<br />
2.2888<br />
56.656<br />
2.2306<br />
0.856 13.157 12.301 11.445<br />
21 0.0337 0.5180 0.4843 0.4506<br />
⁄ 4 11 {<br />
1.479<br />
0.0582<br />
65.710<br />
2.5870<br />
64.231<br />
2.5288<br />
62.752<br />
2.4706<br />
0.856 16.662 15.806 14.950<br />
21 0.0337 0.6560 0.6223 0.5886<br />
⁄ 2 11 {<br />
1.479<br />
0.0582<br />
75.184<br />
2.9600<br />
73.705<br />
2.9018<br />
72.226<br />
2.8436<br />
1.162 20.955 19.793 18.631<br />
23 0.0457 0.8250 0.7793 0.7336<br />
⁄ 4 11 {<br />
1.479<br />
0.0582<br />
81.534<br />
3.2100<br />
80.055<br />
3.1518<br />
78.576<br />
3.0936<br />
1.162<br />
0.0457<br />
22.911<br />
0.9020<br />
21.749<br />
0.8563<br />
20.587<br />
0.8106<br />
3 11 {<br />
1.479<br />
0.0582<br />
87.884<br />
3.4600<br />
86.405<br />
3.4018<br />
84.926<br />
3.3436<br />
1.162 26.441 25.279 24.117<br />
31 0.0457 1.0410 0.9953 0.9496<br />
⁄ 2 11 {<br />
1.479<br />
0.0582<br />
100.330<br />
3.9500<br />
98.851<br />
3.8918<br />
97.372<br />
3.8336<br />
1.162<br />
0.0457<br />
30.201<br />
1.1890<br />
29.039<br />
1.1433<br />
27.877<br />
1.0976<br />
4 11 {<br />
1.479<br />
0.0582<br />
113.030<br />
4.4500<br />
111.551<br />
4.3918<br />
110.072<br />
4.3336<br />
1.479 33.249 31.770 30.291<br />
41 0.0582 1.3090 1.2508 1.1926<br />
⁄ 2 11 {<br />
1.479<br />
0.0582<br />
125.730<br />
4.9500<br />
124.251<br />
4.8918<br />
122.772<br />
4.8336<br />
1.479<br />
0.0582<br />
37.897<br />
1.4920<br />
36.418<br />
1.4338<br />
34.939<br />
1.3756<br />
5 11 {<br />
1.479<br />
0.0582<br />
138.430<br />
5.4500<br />
136.951<br />
5.3918<br />
135.472<br />
5.3336<br />
1.479 41.910 40.431 38.952<br />
51 0.0582 1.6500 1.5918 1.5336<br />
⁄ 2 11 {<br />
1.479<br />
0.0582<br />
151.130<br />
5.9500<br />
149.651<br />
5.8918<br />
148.172<br />
5.8336<br />
1.479<br />
0.0582<br />
47.803<br />
1.8820<br />
46.324<br />
1.8238<br />
44.845<br />
1.7656<br />
6 11 {<br />
1.479<br />
0.0582<br />
163.830<br />
6.4500<br />
162.351<br />
6.3918<br />
160.872<br />
6.3336<br />
Copyright 2004, Industrial Press, Inc., New York, NY
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