These series are obsolete.
The pitch is the reciprocal of the number of threads per inch. The depth is 0.64033 × the pitch. The tap drills suggested below are for, roughly, a full thread.
| Diameter inches |
BSW | BSF | ||
|---|---|---|---|---|
| Threads per inch |
Tap drill |
Threads per inch |
Tap drill |
|
| 1⁄16 | 60 | 57 | — | — |
| 3⁄32 | 48 | 50 | — | — |
| 1⁄8 | 40 | 40 | — | — |
| 5⁄32 | 32 | 31 | — | — |
| 3⁄16 | 24 | 28 | 32 | |
| 7⁄32 | 24 | 17 | 28 | |
| ¼ | 20 | 9 | 26 | 4 |
| 9⁄32 | — | — | 26 | C |
| 5⁄16 | 18 | ¼ | 22 | G |
| 3⁄8 | 16 | 5⁄16 | 20 | P |
| 7⁄16 | 14 | T | 18 | 3⁄8 |
| ½ | 12 | Z | 16 | 7⁄16 |
| 9⁄16 | 12 | 15⁄32 | 16 | ½ |
| 5⁄8 | 11 | 17⁄32 | 14 | 14 mm |
| 11⁄16 | 11 | 19⁄32 | 14 | 39/64 |
| ¾ | 10 | 41⁄64 | 12 | 17 mm |
| 13⁄16 | 10 | 45⁄64 | 12 | 23⁄32 |
| 7⁄8 | 9 | ¾ | 11 | 20 mm |
| 15⁄16 | 9 | 13⁄16 | — | — |
| 1 | 8 | 55⁄64 | 10 | 23 mm |
| 1 1/8 | 7 | 63/64 | 9 | 26 mm |
| 1¼ | 7 | 1 7/64 | 9 | 29 mm |
| 1 3/8 | 6 | 1 11/32 | 8 | |
| 1½ | 6 | 1 9/16 | 8 | 35mm |
| 1 5/8 | 5 | 1 25/32 | 8 | |
| 1¾ | 5 | 8 | ||
| 1 7/8 | 4.5 | 7 | ||
| 2 | 4.5 | 7 | ||
| 2 1/8 | 4.5 | |||
| 2¼ | 4 | 6 | ||
| 2 3/8 | 4 | |||
| 2½ | 4 | 6 | ||
| 2 5/8 | 4 | |||
| 2¾ | 3.5 | 6 | ||
| 2 7/8 | 3.5 | |||
| 3 | 3.5 | 5 | ||
| 3¼ | 3.25 | |||
| 3½ | 3.25 | |||
| 3¾ | 3 | |||
| 4 | 3 | |||
| 4½ | 2.875 | Never defined. | ||
| 5 | 2.75 | |||
| 5½ | 2.625 | |||
| 6 | 2.5 | |||
There existed as well a separate set of BSW form threads used only on bicycles (these are distinct from the BSC or CEI series):
| Major diameter inches |
Threads per inch |
|---|---|
| 7/16 | 20 |
| ½ | 20 |
| 9/16 | 20 |
| 5/8 | 20 |
| 11/16 | 20 |
| ¾ | 20 |
Dimensions of Whitworth’s original proposals.
British Standard 95-1919. Corrections to Effective Diameter required to compensate Pitch and Angle Errors in Screw Threads of Whitworth Form, Tables of.
British Standard 190-1924. British Standard Whitworth (B.S.W.) Bright Hexagon Bolts, Nuts, Set-Screws, Split-pins, Washers and Studs, Dimensions. Addendums in June 1928 and September 1932.
British Standard 193-1929. British Standard Whitworth Small Hexagon (B.S.W.S.) Bright Hexagon Bolts, Nuts, Set-Screws, Split-pins, Washers and Studs. Addendum Sept. 1932.
British Standard 84-1940. Screw Threads of Whitworth Form. (Incorporating B.S. 92).
British Standard 84:1956.
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Last revised: 17 February 2008.