British Standard Fine

From Wikipedia, the free encyclopedia
Jump to: navigation, search

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]

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.

BSF threads use the 55 degree Whitworth thread form.

fractional inches decimal inches thread per inch BSC match Jaw mm exact or ~inch drill for tap
3/16 0.19 32tpi `= 8.59mm 11/32" 6pt 5/32"
7/32 0.22 28tpi  ?  ? 4.6mm
1/4 0.25 26tpi `= 11.30mm -- 5.3mm
5/16 0.31 22tpi 13.34mm 17/32" 17/64"
3/8 0.375 20tpi 15.24mm 5/8" 8.2mm
7/16 0.44 18tpi 18.03mm -- 9.7mm
1/2 0.50 16tpi 20.83mm 13/16 7/16"
9/16 0.56 16tpi 23.37mm 15/16 1/2"
5/8 0.63 14tpi 25.65mm 1" 6pt 14mm
11/16 0.69 14tpi 27.94mm 1'1/8" 6pt 15.5mm
3/4 0.75 12tpi 30.48mm 1"1/4 6pt 16.75mm
7/8 0.88 11tpi 33.02mm 1"5/16 25/32"
1" 1.00 10tpi 37.59mm 1"1/2 22.75mm
1⅛" 1.13 9tpi 42.42mm 1"11/16 26.50mm
1¼" 1.25 9tpi 47.24mm 1"7/8 28.75mm
1½" 1.50 8tpi 56.39mm 2"1/4 34.50mm

References[edit]

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

External links[edit]