Threading a threadless fork
 

I posted a short while back about replacing the fork on my friend's very large frame. I've been trying to keep it threaded, but it requires at least 256mm of steerer. I have a threadless fork cut to length and filed that I want to thread. It has the appropriate ID and very thick tube walls. I thought I could do this at my local coop, but it turns out the die they have has no kind of guide (like the current Park tool, for example, has). Can anyone think of a way to get the threads started reasonably accurately? I have a few more local bike shops/framebuilders I can ask, but so far no luck. Has anyone ever had experience asking a machine shop for this kind of work?

Thanks

Are you asking if anyone has any experience in asking someone else for help,

to do a job that they do as part of their business?

Keep looking for a shop with the proper guided threading die. Most steerer threading dies are intended to chase (clean up) damaged existing threads or extend the threaded length, not thread a completely threadless steerer. A lathe could do the threading but I have no idea how you could mount a fork in a lathe with the steerer end exposed.

RE setup, I'd think the situation would be reversed , The threading die in the lathe chuck , it rotating,

and rather than the tool post stationary and fed into the piece, and the work rotating,


the fork clamped and aligned onto the carrier, moving into the rotating cutter.

Good luck cutting new threads with a die. It's real easy to have the metal just peel off the steerer and not cut full and well formed threads. I've extended threads further down forks many times and have had only so so results. This is using maybe 6 or 8 different dies of various manufactures and age on forms made of both cromo and basic 1020ish steel. I no longer will quote for this service.

Here's a link to another bike forum showing how to set up a fork on a lather for single pointing. Andy.
http://www.velocipedesalon.com/forum...g-33613-3.html

Machine shop is the answer, but it won't be cheap if they do good work.

I wasn't thinking of using a die in the lathe but more along the lines of the set up Andy linked to.

well there a picture was offered.., my father the machinist died years ago ..

I do this all the time for $25.00 plus return postage. However, I won't do keyways for love or money. If you don't find anybody local, consider this the floor price to beat.

The dies sold by Campagnolo, Cobra, and Silva are 100% designed, and of sufficient quality to cut virgin threads when used properly and with the correct handle. These were made for sale to framebuilders, who cut and threaded their own steerers.

One rough way of judging the quality of a die, and deciding whether it's can be used to start new threads is whether it's split, or not. The issue isn't that split dies are low quality -- some are, some aren't -- but that of maintaining concentricity.

A non-split die, is ground flat and concentric to the face and rim, and fits snugly into a handle made to work with it. Split dies often aren't "qualified" as perfectly square to the face, but much more important lose concentricity to the handle when the diameter is adjusted at the split. If the die isn't concentric (dead on concentric) to the axis of the guides in the handle, it will not cut proper threads, and can actually destroy threads that were fine before.

BTW- Years ago I had a very nice Italian, split die and guided handle. The die's OD was ground conical, and fit into a tapered pocket where the size was adjusted by means of a nut that pushed it deeper. This allowed size fine tuning, yet preserved concentricity.

Sadly after cutting hundreds of forks, it gave up the ghost, and with the maker long gone, it meant the tool was dead.

Thanks for the help everyone. ESpecially FBinNY, you're always such a solid source of information. I finally finished the project! After calling nearly all the local shops and a couple framebuilders, it turned out the LBS physically closest to me was willing to thread the fork for $30. They did a little bit of a rough job, but it was good enough to set the headset up properly.

This project was such a mess! Definitely a good learning experience for me to check compatibility of every variable. Because nearly everything that could be incompatible was.

-Steerer length: too long! Bought one threaded fork that was just 7mm to short. Had to custom thread a threadless fork (or use a long threadless fork and a new headset/stem).
-Headset thread pitch: original was 26TPI Raleigh. Had to get a new headset for standard 24tpi.
-Wheel size/clearence: New fork did not have clearence for the 27" 1-1/4" tire that was originally on the bike. I gave my friend a 700c wheel and a 23mm tire. Thankfully they were spares I happened to have. Bonus points on the better braking on the aluminum brake track.
-Brake reach: The original fork was designed for standard reach centerpulls. I had to give my friend a spare sidepull I had in my parts bin. Bonus is that the between the dual pivot, kool stop pads, and aluminum rims, the front braking is infinitely better.
-Crown race diameter: New fork is 26.4mm, and I could only find complete 27mm crown race headsets at the coop, so I had to buy a new headset.

At least the head tube ID was normal?

I also donated way too many parts, and I'm going to eat the cost of a lot of this because I didn't consult my friend about everything--I was just determined to get the bike back on the road. The welded fork looks a little funny on the lugged frame, as does the modern pseudo-aero black rim, and black spokes, but frankenbikes are clearly the new hotness. On the plus side, the bike is now meaningfully lighter, and will stop a whole lot better, particularly in the rain. And I got a lot of experience out of it.