smovlov

Are any of these interchangeable or are they all different? I am assuming they are different. I also read that you can thread a British freewheel on an Italian hub. After that though you have to use a British freewheel. Is this true?

sfclearwater

According to Sheldon they have a slightly different spec:

ISO 1.375" x 24 tpi
English 1.370" x 24 tpi


Although strangely enough he lists them as the exact same here:


https://www.sheldonbrown.com/gloss_bo-z.html#british
https://www.sheldonbrown.com/gloss_i-k.html#iso


Anyway I have always heard that you can change them up, but don't keep switching back and forth.

HillRider

ISO and English are IDENTICAL and, in fact ISO accepted English threading as it's standard. The numbers you quote are the same thing, just expressed a bit differently.

Italian threading is almost identical and English and Italian components will interchange. There is a minor difference in the apex angle of the threads with English threads having a 60° included angle and Italian threads a 55° angle. You can substitute one for another but it is not recommended you go back and forth. If you thread an English freewheel onto an Italian threaded hub, use English threaded freewheels thereafter.

French threading is different in both diameter and thread pitch from both English/ISO and Italian and won't interchange with either.

sfclearwater

Ah, that makes sense. This page threw me a bit:

https://www.sheldonbrown.com/freewheels.html

It lists British and ISO as very slightly different thread sizes. But the question was about Italian threading so I was way off anyway.