Originally Posted by gugie

French: 35 x 1mm
Italian: 36 x 24tpi

Originally Posted by Steel Charlie

indeed - 1mm difference and 24tpi over the 25.4tpi

seems like 30-40 years ago this was done for blitzed French and considering if I heard about it then it must have been fairly common knowledge

Originally Posted by 3alarmer

...it is still done for any of the other BB threadings that are smaller when they are beyond redemption. I have done it myself recently, with a rusted BB in English threading without much threading left. But it's pretty hard on your taps to run an Italian set through a French BB without first reaming it out a little. I guess you can do it, but it's not standard practice.