Tuesday, 10 May 2011

Fixing stripped threads on a Sturmey X-FD axle

A while ago I bought a Sturmey Archer X-FD 70mm Front Drum brake hub off ebay. I got it a bit cheaper than one would normally go for because the threads on either end of the axle were damaged. Presumably from somebody forcing either the wrong nut onto the axle or over tightening a small domed nut - most likely the later.
The damaged section of threads did not extend too far, but did mean it was impossible to fit a nut or remove the ones still on the axle. The solution was to recut the damaged threads using a thread cutting set. Except it wasn't quite that easy because the Sturmey Archer axle appears to use an M9/1 thread. Needless to say our thread cutting set doesn't have a cutting bit for this size.

So instead the damaged threads got cut with a smaller M8/1 thread. This way they would still be the correct pitch, but at a smaller diameter, meaning the axle nut could screw over the damaged area and reach the undamaged threads further on.

The same technique could be applied to any valuable but damaged hub axle if needed.


  1. An ingenious approach, especially for non-Sturmey parts where the replacements can often be difficult or impossible to source.

  2. You want to get a thread file for repairing damaged threads Jim.

    You would loose less material by gently filing back just enough of the thread.

  3. Saying that, on something like an axle, is it not worth playing it safe & getting a replacement?

  4. Yep ... don't have one though! :-D There's loads of axle sticks out each side on these, just needed to be able to get a nut on there and this did the job. Not worth replacing when it's only the last 5mm of each end.