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British Standard Whitworth (BSW) is an imperial-unit-based screw thread standard, devised and specified by Joseph Whitworth in 1841 and later adopted as a British Standard. It was the world's first national screw thread standard, and is the basis for many other standards, such as BSF , BSP , BSCon , and BSCopper .
A screw thread is an inclined plane wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread. More screw threads are produced each year than any other machine element. [1] Threads are generally produced according to one of the many standards of thread systems.
The thread form follows the British Standard Whitworth standard: Symmetrical V-thread in which the angle between the flanks is 55° (measured in an axial plane) One-sixth of this sharp V is truncated at the top and the bottom; The threads are rounded equally at crests and roots by circular arcs ending tangentially with the flanks where r ≈ 0 ...
BS 92 Screw threads, British Standard Whitworth and their tolerances; BS 93 Specification for British Association (B.A.) screw threads with tolerances for sizes 0 B.A. to 16 B.A. BS 94 Watertight glands for electric cables; BS 95 Tables of Corrections to Effective Diameter required to compensate Pitch and Angle Errors in Screw Threads of ...
In 1841, Joseph Whitworth created a design that, through its adoption by many British railway companies, became a standard for the United Kingdom and British Empire called British Standard Whitworth. During the 1840s through 1860s, this standard was often used in the United States as well, in addition to myriad intra- and inter-company standards.
Whitworth screw sizes are still used, both for repairing old machinery and where a coarser thread than the metric fastener thread is required. Whitworth became British Standard Whitworth, abbreviated to BSW (BS 84:1956) and the British Standard Fine (BSF) thread was introduced in 1908 because the Whitworth thread was too coarse for some ...
BS 93:1951 — Specification for British Association (B.A.) screw threads with tolerances for sizes 0 B.A. to 16 B.A. BS 93:2008 — British Association (B.A.) screw threads — Requirements The angle of the thread is 47.5° [ 4 ] : 2 and the depth of thread is 0.6 times the pitch with rounded tops and bottoms.
Many thread sizes have several possible tap drills, because they yield threads of varying thread depth between 50% and 100%. Usually thread depths of 60% to 75% are desired. People frequently use a chart such as this to determine the proper tap drill for a certain thread size or the proper tap for an existing hole.