Convert ITA threaded steer to ISO

[mujirushi]

Hi everyone, I tried searching but not too sure what keywords I should be using, so didn't find any results...

I have a factory threaded Colnago Precisa fork (new 2021 stock) (which I think is ITA threaded), and been trying to mate it with a Campagnolo Record Threaded headset (new 2021 stock) (ISO/English Threaded I believe)... Very tight at the 4th / 5th turn.

This leads me to believe it is to do with the ITA vs English thread being not entirely compatible...

For future parts availability sake, is it possible to convert the thread on the steerer from ITA to English thread?

I have been going round different Facebook groups and LBS, all have different opinions. So would like to seek more internet wisdom.

Thank you very much for your helps!

 

[mdvineng]

ITA and English are interchangeable, only French headsets cause issues. I would thoroughly clean both threads as just a little dirt will cause issues. Pitch and diameter are the same, only the thread angle is slightly different.

 

[mujirushi]

Thanks. Pretty sure neither would be French thread...

Would it hurt to get LBS to trace the thread with an ISO die?

 

[Midlife]

Wouldn't hurt but I'd try first as they are interchangeable, while I'm thinking. Isn't the Italian and ISO crown races a slightly different size?

 

[mdvineng]

Wouldn't hurt but I'd try first as they are interchangeable, while I'm thinking. Isn't the Italian and ISO crown races a slightly different size?

Same dia, thread angle varies from 60 to 55°, class B fit, all good.

 

[Midlife]

I was thinking more of the crown race size rather than the threads ..... Slopes off to Sheldon Brown

 

[danson67]

Yes, Italian thread is different thread angle, but pitch is the same, so ideally run an ISO die down the thread to shape, and cut the crown seat down to ISO (26.4mm).

Italian crown race is either ( ) 26.5 or 27.0mm.

All the best,

 

[mujirushi]

Cool I will do that

Crown race.... it's been seated for me already by the supplier. Didn't understand why they didn't thread the thing for me