Fissile

Most bikes shops won't take on a repair like this at all...even if they had the tools and skills...which as you mentioned, most don't. They would make very little money on such a job and they don't want the liability. The OP shouldn't listen to the Chicken Little types either I've repaired buggered threads on hundreds of fasteners...cars, motorcycles, bikes, this is no big deal. A file or belt sander will work. Use a steel nut the first time and the OP will be fine.

Gresp15C

I've done this with a triangle file. Another trick is to use a regular diameter tap with the same thread pitch as a scraper when you've got it nearly all cleaned up. At most you're going to lose one thread, but it's worth assuming that the top of a steering tube has been cut with a hacksaw and cleaned up with a file at least once in its life.

My own rule is that I'm not done until I can thread the nut on smoothly past the repair, by hand without requiring a wrench.

rosefarts

Do you have a steel nut that will fit? Just in case it's something odd, like French. It's worth finding out.

WizardOfBoz

I think that the consensus here is that getting a die on the fork is more likely to mangle things than to fix them. So I'm not sure if it matters if the thread is 24 tpi ISO or 1mm (French).

I offered the thought of using a thread chasing file, and others have pointed out that the length of thread that is knackered is so slight, one might do better with a triangular hand file. I think that's probably right. In any case, if the OP goes at the threads with a file it should be done with a very light touch, and a very small triangular file, to get the thread root cleaned out.

Phil_gretz

OP here. I really, really appreciate everyone's comments on this thread. I've held off doing anything without having thought it through carefully.

I don't have a steel steerer nut lying around. Funny, tons of bottom brackets and locknuts, but I rarely harvest headset. If I'm going to donate a frame and fork, I leave the headset in place for the next owner to use...

Looking at my meager selection of small files, I do have one or two that could work. So, I'll report back once the deed is done. Phil

WizardOfBoz

If you want really good small files, check out Gesswein. Triangular ("Three square") files available from about 5 to 20 bucks. Gesswein, Grobet, other brands here.

https://www.gesswein.com/p-9909-grob...ee-square.aspx

rosefarts

I get that. I'm commenting on the idea of running a steel nut down the tube once the file work is done. Getting the right nut could be laughably easy or almost impossible.

Fissile

It's laughably easy. The cup and crown race are JIS, the threaded bits are same as ISO. https://www.ebay.com/itm/New-Old-Sto...ss!07607!US!-1

Just about any kid's bike you can find out on garbage night will have a 1 inch threaded headset that can be stripped for the required threaded bit.

trainman999

You could easily make a tool for this problem take a steel headset jam nut and cut it in half, put the pieces together below the damaged threads wrap a piece of tape around it to hold it in place, use aan adjestable wrench or a c clamp to hold it tight and turn off. Use the adjestable cup to make a thread chaser cut 2-4 groves in the threads run it down the threads to clean out the gunk. Do the same with a set of bb cups.

rccardr 

That's very thinky!

Phil_gretz

Okay. After a week of coming back for careful and judicious filing, I have the first two threads clean enough to attempt a steel steerer nut.

Phil_gretz

This was hand threaded. It's an encouraging sign.

I'll attempt the aluminum Campy nut after a few more runs with the steel nut and machine oil...

rccardr 

Nice work, Phil!
That’s a lovely Sachs frameset, who did the respray?

Phil_gretz

Doc, I don't know. It's for a friend local here in DC. He had sent it out originally, and the painter did not attempt or complete the job. I'm not sure of the circumstances. He then sent it to a different painter. I'll ask him next time we correspond. He's been extremely patient to complete the build, since the paint step has taken nearly two years, I think he said. Phil

Phil_gretz

WHOO-HOO!!!