bulgie 

What's the length of your existing steerer? I know it's a longshot, but maybe we can swap. I'm looking for a PX-10 fork for a tall frame, needs to be 240 mm from the crown race seat up. I have three PX-10 forks with shorter steerers, maybe one that could work for you?

I also have a French (M25 x 1) steerer die, but like a couple folks who have posted already, I've found threading steerers to be risky. I've had success (did one just last week), but also failures, where the new threads are just torn out at the root as you screw the die back off. I find a strong correlation between success rate and how many threads you cut: The die comes off clean, threads perfect, if you keep the number of threads (threaded length) to a minimum, somewhere around the height of the die itself. Long threaded length = almost guaranteed failure.

I have cut steerer threads on a lathe, using a single-point tool. That's the best way of all, very reliable, but I don't have a lathe at the moment. Maybe bring your fork to a machinist and get a quote? Might cost more than a PX-10 is worth. No insult intended, I like them, but they are not super valuable, you can just buy another one. That might only be feasible if you have a buddy who has a lathe and likes a challenge. Due to the offset (rake), the weight of the dropouts makes the lathe shake when spinning a fork, so this would not be a project for a mini-lathe. It needs to be a heavy enough machine to do it well. Also some older American lathes can't cut metric threads, or can do it but only after partially disassembling the gear train and installing "change gears" with different numbers of teeth, that your machinist might not even own.

Another option that I'm fond of is a "thread-less" headset. Not threadless, you still need some threads, but only a few, 10 mm or even less. You still use a quill stem. The trick is to use the upper cup of a threadless headset, and it goes on the unthreaded part of the steerer. That can be made from an existing threaded headset by simply removing the threads. Best done on a lathe for precision, but a few people have reported success with just grinding out the threads with a Dremel. The existing threads serve as a visual guide; just grind away metal until the threads just barely disappear. This method takes patience and good hand-eye coordination. Not for everyone!

Then you need some way to lock in the headset adjustment. A single, normal threaded headset nut at the top can work with Loctite, but I prefer a two-nut method where a thin jam nut is tightened against the top nut. In your case both nuts would have to be M25 x 1 and such nuts aren't common, so you might have to make one yourself by thinning a vintage French headset locknut. At a minimum, you need to remove the flange at the top of the nut that keeps it from threading down past the top of the steerer.

Here's an example of a two-nut solution, in English thread:


The bike is an indoor trainer, a small frame with a way-too-long steerer and an adjustable Look Ergostem that we had lying around. The stem is quill style, which is why we didn't just use a threadless stem, needed that adjustability. The Ergostem allows one frame to fit multiple sizes of people with just a quick adjustment.

There's only maybe 12 mm of threads there, well within the range of what I feel I can cut safely with a die, and if you keep the two nuts thin, you can use even fewer threads. That jam-nut, that takes the hook spanner, is Japanese, came on cheap bikes in the '70s — uncommon to find one nowadays, and definitely unobtainium in French thread. You'd have to make your own jam-nut. Leave out the washer that you can see in the photo, not necessary if you're trying to minimize the number of threads.

There are also single-nut solutions that use a slit and a pinch-bolt, or a setscrew (grub screw). But again hard to find in French.

Mark B