The unlimited forms of threads which may be used has brought about efforts to standardize the form and pitch of the V thread. The efforts have resulted in the U. S.
D = 90 Pitch standard for the United States, the Whitworth standard for England, and the metric or international standard for Continental Europe.
The form of the U. S. standard is shown in Fig. 185.
The form of the Whitworth standard is shown in Fig. 186.
The pitch of threads is standardized by designating a definite pitch for threads cut on a cylinder of specified diameter; i. e, a bolt 1/2-inch diameter has 13 threads per inch, and a bolt of 1-inch diameter has 8 threads per inch by the U. S. standard.