Originally Posted by
Chombi
the difference between English and Italian threading is a slight difference in thread pitch. One thing I keep hearing about using the two different threadings with each other is to try not to remove and reinstall the components too much after the first time you install it. I guess there might be a high possibility of cross threading the parts if you do. Mixing the two can be done but matching the threads is always the better way to go to avoid problems.
Chombi
Pitch is the same 24 TPI (Threads Per Inch). British threads are 60° but Italian threads use the older British 55° thread angles.
The British standard and now ISO standard is 1"-24TPI. Italian headset threads were 25.4mm x 24TPI, almost the same.
You can easily force fit one on to the other but don't change Italian with British back and forth.
Also fitting a British aluminum alloy headset on an Italian steerer or vise versa can damage the aluminum threaded parts.
Chas. verktyg