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British Standard Fine (BSF) is a screw thread form, as a fine-pitch alternative to British Standard Whitworth (BSW) thread. It was used for steel bolts and nuts on and in much of Britain's machinery, including cars, prior to adoption of Unified , and later Metric , standards.
The design was first proposed by the British Association in 1884 [1] [2] with a thread angle and depth based on the Swiss Thury thread, [3] it was adopted by the Association in 1903. The Thury thread was different in that it went both positive and negative all the way up to a size of −20 which was 75.2 mm diameter by 8.23 mm pitch ( p ).
Prior to this, sewing patterns were made to fit a specific individual, and were originally made on cloth, and only later on paper. A tailor or dressmaker recorded a customer's measurements on a thin strip of parchment and kept it with the pattern pieces, noting any changes in measurements and adjusting the pattern pieces accordingly.
The common V-thread standards (ISO 261 and Unified Thread Standard) include a coarse pitch and a fine pitch for each major diameter. For example, 1 ⁄ 2 -13 belongs to the UNC series (Unified National Coarse) and 1 ⁄ 2 -20 belongs to the UNF series (Unified National Fine).
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.
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 ...
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 .
The term fine adjustment screw typically refers to screws with threads from 40–100 TPI (Threads Per Inch) (0.5 mm to 0.2 mm pitch) and ultra fine adjustment screw has been used to refer to 100–254 TPI (0.2 mm to 0.1 mm pitch). These screws are most frequently used in applications where the screw is used to control fine motion of an object.