Hi - I've got some 1" forks that I'd like to use for some projects, but need to extend the threaded section. Park tool sells a 1" 24 TPI tool for $250.

1" 24 TPI dies are also available separately for 10 times less.

Does anyone know if using a generic 1" 24 die would work (provided I go slow and use oil, etc.)? Anyone know what the pitch (fine vs course) is on a standard fork? Thank you.

I bought an $8 1"x24tpi die on ebay last month, used it to extend the threads on a steer tube yesterday, and am fairly sure I destroyed the fork's usability. It removed way too much material. I've never had that problem with the Park die. Can't comment on a $25 die, but don't get an $8 die.

The pitch on a standard fork is 24 threads per inch. This is a fairly fine pitch. The standard pitches for a 1" diameter are 8tpi (UNC-unified national coarse) and 12tpi (UNF-unified national fine). Bicycle forks use finer threads than the UN standard, probably because coarser threads are deeper, and would require thicker material.

Best done on a lathe in my opinion. It's hard enough chasing existing steerer threads with a hand die, let alone cutting new threads. It can be done by hand but a lot of torque is required. If you are going to try it out, have the fork clamped well in a fixture at multiple points. Use a long tap handle. Do not put the die in a vise and twist the fork blades to turn the steerer - good chance of tweaking the blades out of alignment.

Check with Mike Terraferma - he's got a Silva-made machine called the La Combinata. I've seen it perfectly add threads to a threadless 1" fork.

I have the Hozan tool with the die holder and guide, but have never tried to use it to start threads.

-Kurt

The 1" x 24tpi die should be fine. If your die stock is unpiloted, you need to be careful to keep it on axis. This is more of an issue when threading an unthreaded tube; extending threads allows the existing threads to pilot the die to a large extent, but it still pays to be careful.

Not sure what you're asking here. 24tpi is the pitch for an English/ISO standard 1" threaded steer tube.

When making my fork at the UBI framebuilding school, they were out of super long threaded steerers (my frame had a very long head tube). I was given an unthreaded 1" steerer and a Park HS threading tool. It took a lot of effort, I had to stop and rest my arms and shoulders a few times, but it was doable.

I've also ruined a fork once that needed threads extended. The top wasn't square, and I started the threads off axis, ended up ruining it, so follow John's advice, above if you're doing this.

The split dies are an important part of the bike specific ones I Think. That combined with the adjustable die stock to tweak the fit make a difference.

Just spitballin' here, but I wonder if using an old disused top race, flipped upside down, to "follow" the die as you go would help keep it on axis.

I couldn't begin to count how many steerers I've extended threads on.....use a lot thread cutting oil. I use to clamp forks in a vice.

1) make sure the current threads have absolutely no debris or corrosion in them, clean thouroghly with a wire brush and solvent.

2) when cutting new threads, take small passes, back-up frequently to remove the metal chips with a brush, apply more cutting fluid and continue.

1 step forward, 2 steps back and I use anti-seize with cutting oil.

As always, patience is key and check your work as you go.

I got the Hozan tool tool cheap, with extra bits, used it once so far to extend the threads on a steerer - was my first time, but I know how to use a diestock and had no problems If you've used a small one enough to know what you are doing it's no different, just more work.

And yes, a good die is worth what it costs. Cheap ones are cut then hardened and they can distort during the hardening process. Good ones are hardened and then ground.

I have a Gavan 1" - 24 that I've used to extend threads on a steerer. It takes a lot of effort but results are good. I clamp the fork crown into my hefty wood vise and use a lot of cutting oil. The die cost me about $35.

Machine shop - cheaper than a $250 tool
Machine shop - much higher quality than a $35 tool.