Originally Posted by
repechage
The Origin8 is most likely ISO, or very close to "British" threaded. The fork is most likely Italian. Same diameter, same pitch but different thread profile. I forget but one is 60° and the other has a 55° inclusive angle to the thread profile, and one is slightly rounded the other not.
So… Go Italian, or have the steerer chased with a British threaded die.
Just to be sure its not the headset, find a known English threaded steerer and check the fit of the threaded parts.
Source: Sutherland's 4th Edition
Right. An English/ISO headset on an Italian thread steer tube is a "class-B" fit; it will work, but avoid going back and forth between fully compatible ("class-A") and "class-B" headsets. If the headset you choose has aluminum threaded parts, no worries. The steel steer tube will re-form the aluminum threads into proper 55° Italian threads.