Best Way to Repair Forks Threads?

[VeryFEDUP]

Hello All. Not signed in for a while but do look in and marvel at your projects from time to time! I have a small project here:

That is the threaded section of some steel bicycle forks. I got them to replace forks damaged in a fight with a Mercedes! As you can see, a section of the threads are FUBAR probably caused by a loose headset. Steel is possibly 531 Reynolds; certainly the blades are.
Forks with the steerer length I need for my frame appear to be few and far between. I was wondering if they can be repaired?
I thought some sort of braze, trying to keep the heat localised as best as possible. I have a friend with a Harrison lathe who can turn it down for me. I think I have found a die of the right size for the final stage.

Is this a viable plan? Is there a better way? Would braze have enough strength for this application?

Thanks in advance.

 

[stuvy]

@Shox Dr dave might be able to help

 

[pedrobedro]

If you could get a die the right size it would clean up by the look of it, might take some finding though.

 

[Brad93]

This is one for @Shox Dr

brazing would work but I’m unsure of the strength you’d get and you’d have to turn all the old rusty thread off first. What wall thickness would that leave? Not a lot I’d imagine.

You could try picking up the existing thread and threading it in the lathe. Repair just the damaged area.

 

[Ashley Burton]

I bet a decent bicycle shop might have a die to repair those threads

 

[Matchless]

I would run a die down it and then try to space the nut to end up above the damage, tracy tools may be able to help with a die if you don't have one,

 

[Pete.]

You can't cut the damaged thread off the end?

 

[The_Yellow_Ardvark]

Evans Cycles used to a repair service on item like that for a few pounds.

Not sure if they do now. But worth a call.

 

[Agroshield]

I would run a die down it and then try to space the nut to end up above the damage

Seconded.

Clean up the threads and then perhaps try to make a longer or a double nut so it grips above and below the damaged part.

There seems to be a lot of unused thread lower down. Is there any opportunity to reduce the thickness of something at the bottom of the stem or frame so the forks sit higher in the frame and thus the standard nut is on a lower, undamaged section.

 

[winchman]

A good bike shop will have a die, clean them up and see how they are.
In the past I just made a new one and Tig welded it on.

 

[Shox Dr]

It take it, its a road bike with rigid forks and the stem is welded to the forks.
Old style threaded headset. So the stem can not be cut down, nor a bigger nut used.
So, if the threads wont clean up sufficiently to get a good grip with the nut and a Aheadset isn’t available. Then possibly gas bazing to build up the thread just enough to fill the threads, dress and recut with a die.

It used to be a common problem with poorly adjusted bearings, the threads wear on the top bearing cup. I would have thought a good old school bike shop will fix it either way.

 

[Craig-SM]

A neighbour had this problem and his local bike shop couldn’t rethread it. He took it to an engineers and they cut the steerer tube at the half way point, flipped the threaded end to the middle, internal sleeved it before welding and milling off the excess weld. The bike shop then applied new threads. He still rides the bike regularly so assume he’s not had problems since.
A mate did similar and cut down his steerer on an expensive set of suspension forks without allowing for the headset making it too short. A guy at his work welding in the piece he’d cut off into the middle and he was able to cut it to the correct size.

 

[Shox Dr]

A neighbour had this problem and his local bike shop couldn’t rethread it. He took it to an engineers and they cut the steerer tube at the half way point, flipped the threaded end to the middle, internal sleeved it before welding and milling off the excess weld. The bike shop then applied new threads. He still rides the bike regularly so assume he’s not had problems since.
A mate did similar and cut down his steerer on an expensive set of suspension forks without allowing for the headset making it too short. A guy at his work welding in the piece he’d cut off into the middle and he was able to cut it to the correct size.

Unforuntatley for legal reasons, I would not weld on a steer tube. Many moons ago, MTB was my business. Had a set of forks sent in for service. The bloke got them back and ‘modified’ the steer tube. I spent quite a bit of money, defending something I didn't do, nor had any knowledge of.

Forks are cheap. Go buy some new ones, or find someone with hefty Product indemnity insurance

 

[Ashley Burton]

@Craig-SM That's why I said a 'decent' bike shop

Too many bike shops fit parts & don't know how to repair things. Truing wheels seems to be a dark art to some of them!

The example you gave seems to be quite an extreme case where the threads must of been beyond repair

If a die can't clean up the threads. Then a more serious repair method is needed or you just get another pair of forks

 

[SierraV6]

Is this the die you need (available in two sizes)?

https://uniortools.com/eng/product/1696-fork-threading-tool

Expensive, but I don't know how much you'd pay for replacement forks.

 

[500e]

How is the tube fitted in the crown weld or brazed, one of the frame builders can maybe re tube, did we not have a couple of members who were into cycle frames.

 

[Cobbler]

Are the clamp on headsets still available? I can’t think who used to do them, one of the well known makes to get over the eternal problem of them coming loose.

 

[graffian]

Needle file and see how it all looks after you have tidied the threads.

 

[wacky7791]

i used to be a frame builder for Bob Jackson Cycles years ago, we often fit new steerer tubes to forks when the threads were knackered.
othewise you can get inserts that wedge in like a quill stem but you then use an 'aheadset' style stem and bearing set on them.

 

[wacky7791]

from bob jacksons site (other bike shops are available), though you'll need to factor in repainting them too and it would depend on the crown/leg set up ie are they brazed or welded in