Originally Posted by
juvela
-----a metric threaded gear block cannot thread onto a BSC or Italian threaded hub, it is too small
while a BSC or Italian threaded gear block can thread onto a metric threaded hub
this is an unsatisfactory arrangement as thread engagement is not complete and risks stripping the threads on the hub-----
My first racing bike, given to me by my parents in 1963, was a Helyett track bike, with all French components. It came with a 51-tooth chainring and a 15-tooth sprocket, which made much too tall a gear for climbing the hills north of New Haven.
Switched it for a 19-tooth English-threaded sprocket, which quickly stripped the hub. The mechanic at the local bike shop fixed it by wrapping the hub in aluminum foil, which held surprisingly well, but I wouldn't recommend trying it with a freewheel.