I believe the threads were indeed cut at slightly different angles (55 degrees versus 60 degrees), so there will be a tight fit when crossing nationalities. This would mean that the squeezed or re-chased softer alloy hub threads would then be a tiny bit loose when returning to a proper match.
But, I've never found it a real problem. ~ Just be careful to thread the freewheel on slowly and carefuly to minimize any potential cross-threading damage. This could happen if you were to force the freewheel on only "thinking" that it was aligned - because you'd naturally expect some increased resistence.
On Regina freewheels there were small markings on the rear of the bodyto indicate threading: "FI" = British "FF" = French and, no marks indicates Italian threads.
A different, but similar, threading issue occurs when mounting some derailleurs onto old Campagnolo rear dropout derailleur hangers. Campy dropouts were tapped 10mm x 26 TPI and non-Italian derailleur mounting bolts were generally 10mm x 1.0mm (25.4 TPI). Here, the damage was really more noticeable... but in this case, the dropout threads could also be easily re-tapped for a proper non-Campy derailleur fit.
Bob Hanson, Albuquerque, New Mezico, USA
------------------------------- Steven Willis wrote:
I was always told that it was the angle of the thread was different on the two. But after saying that I have seen them bind up sometimes but not all the time. Maybe the cutter was worn and did not have as good of fit.
--------------------------------- Peter Brueggeman wrote:
Regarding "...Is there any functional downside to using a British threaded freewheel on an italian threaded hub?...,"
Sutherland's sixth edition says "this combination works but avoid changing back and forth between Italian and English Freewheels. Not for strong or heavy riders." --------------------------------