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British Threads - British Standard Fine


BSF (British Standard Fine) Thread Data

Since 1908 this thread, in conjunction with BSW (British Standard Whitworth) has been the mainstay of British Engineering, and was used when finer pitches were required.

Angle of thread = 55°

British Standard Fine (BSF)

BSF Thread Profile

A finer pitch series, analogous to the American Unified Fine (UNF), although - unlike the case of BSW/UNC - with none of the pitches in common with UNF. Many motorcar and motorcycle manufacturers commonly used a lot of BSF threads.

T P IPitch
Tapping Drill Size
3/16320.03130.14755/32 inch
(3.97 mm)
7/32280.03570.173Number drill 15
(4.6 mm)
1/4260.03850.2008Number drill 6
(5.3 mm)
5/16220.04550.254317/64 inch
(6.75 mm)
3/8200.050.311Letter drill P
(8.2 mm)
7/16180.05560.36639.7 mm
(0.3819 inch)
1/2160.06250.427/16 inch
(11.11 mm)
9/16160.06250.48251/2 inch
(12.7 mm)
(0.5512 inch)
11/16140.07140.596115.5 mm
(0.6102 inch)
3/4120.08330.643216.75 mm
(0.6594 inch)
7/8110.09090.758625/32 inch
(19.84 mm)
1 inch100.10.87222.75 mm
(0.8957 inch)