Changing the travel on my Xfusion Trace 34s I have managed to damage the thread on the airshaft so the nut at the foot of the fork won’t go on.
Spares are pretty non existent so I am hoping running a die down it will do the job. However it is a 10mm thread which has three variations of pitch. Any suggestions which it might be or any other ideas to save the fork? There aren’t that many around to source a second hand one

Get an M6 x1 bolt, an M8 x 1.25 bolt and an M10 x 1.5 bolt, as these are the three commonest variations of pitch on M10 threads in my experience.

Ignore the difference in diameters you are only gauging the pitch. Lay the bolts against your forks tbread in turn and see which one lines up with your forks thread. The thread you will require will be M10 x whatever the pitch is on your bolt.

You are then in a better position to try and source a die, but be warned they can be ridiculously expensive.
A cheaper option might be, if the thread isnt totally toast, to run a thread file of the correct pitch against it in the damaged area. Dont worry about taking too mu h off, these tend to just reshape damaged threads rather than cut them.

Another option if you are experienced with them is to use a diamond needle file to tart up the thread. These are 60 degrees, just like a metric thread, but will cut material off unlike the thread file, so be careful you dont take too much off.

Last option, and definitely the least preferred, is if the damaged section is only very small and you have plenty of undamaged thread left, is to file tbe damaged thread off until you get the nut the start.

Excellent advice, thank you

You are very welcome, hope it works for you 👍

Just buy a thread pitch gauge and measure the pitch.
You can get them for around a fiver.

A thread pitch gauge is always a good tool to have and they’re pretty cheap as are tap n die kits or just a specific tap or die along with the handle can be bought off ebay cheap enough, for example I recently bought a die for a left hand pedal thread to clean up a dodgy axle for under a tenner. You can probably get a thread gauge and a feeler gauge for under a tenner, both are good little tools to have for those random issues and checks.

I meant a triangle needle file, not diamond. D’oh.

Measure the gap between 2 high points to determine the pitch.

if you can measure 10 gaps and divide

it is a 10mm thread which has three variations of pitch

You can check the standard pitches with decent metric ruler:

Line up a thread with one of the millimetre marks and see how far away the next millimetre mark that lines up with a thread is –

1mm away = 1.0mm pitch
3mm away = 1.5mm pitch
5mm away = 1.25mm pitch

If you’re looking for parts, this site is good.
https://www.diymtb.com.au/displayItems.asp?cid=78
And i’m sure they’ve sent stuff out to the UK before.
(i’ve actually just spoken to the owner about sourcing the annoyingly odd-sized crush washers for a Trace 36)

In the absence of a pitch gauge I’d measure using an engineers steel rule or a vernier. Assess how many threads are in a measured 10mm section & go from there. What you are looking for is a die nut. A die is used to cut a thread from clean stock & is split allowing the die to be compressed until the correct minor & major thread diameters are achieved. It’s easy if you’re hamfisted to go undersize with these. A die nut is correctly sized & if used properly will remove the damaged material from the thread of your airshaft provided you don’t cross-thread it whilst restarting the thread. Provided it’s not properly graunched there could be enough of the thread left to accept the load from the nut. If I was a gambling man I’d bet on it being 10 by 1mm pitch. Die nuts available on Ebay.

Good luck.