Bottom Bracket Threading

Common Bottom bracket internal threading for cottered, cotterless square taper and splined bottom brackets.

Standard	Thread	Left Adjustable Cup	Right Fixed cup
British	1.370” x 24 TPI	Right Hand Thread	Left Hand Thread
ISO	1.375” x 24 TPI	Right Hand Thread	Left Hand Thread
Italian	36mm x 24 TPI	Right Hand Thread	Right Hand Thread
French	35mm x 1mm	Right Hand Thread	Right Hand Thread
Swiss*	35mm x 1mm	Right Hand Thread	Left Hand Thread
Whitworth**	1 3/8” x 26 TPI	Right Hand Thread	Left Hand Thread

*  Some Motobecane.

** aka Raleigh. Nottingham, Except Carlton and Asian


References

• Big Blue Book of Bicycle Repair by Park Tool; 2013
• Sutherland's handbook for Bicycle Mechanics 7th Edition