British Standard Fine

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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 much British machinery, including cars, prior to adoption of Unified, and later Metric, standards. For highly stressed conditions, especially in motorcycles, a finer thread, British Standard Cycle (BSC), was used as well.

BSF was developed by R. E. B. Crompton, and his assistant George Field.[1] BSF threads use the 55 degree Whitworth thread form. It was introduced by the British Engineering Standards Association in 1908.[2]

The table provides BSF sizes, the threads per inch and spanner jaw sizes. The BSC column indicates where BSF and BSC threads match. The table shows suitable tapping drill sizes. Uncommon sizes are shown in italics.

Table[edit]

Diameter Thread
density
As
BSC?
Nut,
approximate
Tap drill
(in) (mm) (in−1) (mm) (in)
316 0.19 4.83 32 Yes 8.59 1132 6pt 532 in
732 0.22 5.59 28 No 4.6 mm
14 0.25 6.35 26 Yes 11.30 5.3 mm
516 0.31 7.87 22 No 13.35 1732 1764 in
38 0.375 9.53 20 15.24 58 8.2 mm
716 0.44 11.18 18 18.03 1116 9.7 mm
12 0.50 12.70 16 20.83 1316 716 in
916 0.56 14.22 16 23.37 1516 12 in
58 0.63 16.00 14 25.65 1 6pt 14 mm
1116 0.69 17.53 14 27.94 1+18 6pt 15.5 mm
34 0.75 19.05 12 30.48 1+14 6pt 16.75 mm
78 0.88 22.35 11 33.02 1+516 2532 in
1 1.00 25.40 10 37.59 1+12 22.75 mm
1+18 18 457.20 9 42.42 1+1116 26.50 mm
1+14 1.25 31.75 9 47.24 1+78 28.75 mm
1+12 1.50 38.10 8 56.39 2+14 34.50 mm

References[edit]

  1. ^ Glanfield, John (2001). The Devil's Chariots. Sutton. p. 87. ISBN 0-7509-4152-9.
  2. ^ Sidders 1969, p.16

Bibliography[edit]

  • P.A. Sidders, ed. (1969). Guide to World Screw Threads. New York: Industrial Press. ISBN 0-8311-1092-9.

External links[edit]