The standard pitches for the sharp V-thread are as follows:—

SIZE OF BOLT.

1⁄45⁄163⁄87⁄161⁄25⁄83⁄47⁄8111⁄811⁄413⁄811⁄215⁄813⁄417⁄82
Number of Threads to Inch.
201816141211109877665541⁄241⁄2

The following table gives the threads per inch, pitches and diameters at root of thread of the Whitworth thread. The table being arranged from the diameter of the screw as a basis.

Diameter of
Screw.		Threads per
Inch.		Pitch.Diameter at
Root or Bottom
of Thread.
Inch.Inch.
1⁄840 .025 .0929
3⁄1624 .041 .1341
1⁄420 .050 .1859
5⁄1618 .056 .2413
3⁄816 .063 .2949
7⁄1614 .071 .346
1⁄212 .083 .3932
9⁄1612 .083 .4557
5⁄811 .091 .5085
11⁄1611 .095 .571
3⁄410 .100 .6219
13⁄1610 .100 .6844
7⁄89 .111 .7327
15⁄169 .111 .7952
1 8 .125 .8399
11⁄87 .143 .942
11⁄47 .143 1.067
13⁄86 .167 1.1615
11⁄26 .167 1.2865
15⁄85 .200 1.3688
13⁄45 .200 1.4938
17⁄841⁄2.222 1.5904
2 41⁄2.222 1.7154
21⁄841⁄2.222 1.8404
21⁄44 .250 1.9298
23⁄84 .250 2.0548
21⁄24 .250 2.1798
25⁄84 .250 2.3048
23⁄431⁄2.286 2.384
27⁄831⁄2.286 2.509
3 31⁄2.286 2.634
31⁄431⁄4.308 2.884
31⁄231⁄4.308 3.106
33⁄43 .333 3.356
4 3 .333 3.574
41⁄427⁄8.348 3.824
41⁄227⁄8.348 4.055
43⁄423⁄4.364 4.305
5 23⁄4.364 4.534
51⁄425⁄8.381 4.764
51⁄225⁄8.381 5.014
53⁄421⁄2.400 5.238
6 21⁄2.400 5.488

The standard degree of taper, both for the taps and the dies, is 1⁄16 inch per inch, or 3⁄4 inch per foot, for all sizes up to 10-inch bore.

The sockets or couplings, however, are ordinarily tapped parallel and stretched to fit the pipe taper when forced on the pipe. For bores of pipe over 10 inches diameter the taper is reduced to 3⁄8 inch per foot. The pipes or casings for oil wells are given a taper of 3⁄8 inch per foot, and their couplings are tapped taper from both ends. There is, however, just enough difference made between the taper of the socket and that of the pipe to give the pipe threads a bearing at the pipe end first when tried with red marking, the threads increasing their bearing as the pieces are screwed together.

The United States standard thread for steam, gas and water pipe is given below, which is taken from the Report of the Committee on Standard Pipe and Pipe Threads of The American Society of Mechanical Engineers, submitted at the 8th Annual Meeting held in New York, November-December, 1886.