DIY cutting threads into 1" steerer
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DIY cutting threads into 1" steerer
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.
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.
#2
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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.
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.
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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.
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Anyone know what the pitch (fine vs course) is on a standard fork? Thank you.
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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.
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.
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#7
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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.
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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.
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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.
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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.
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.
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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.
As always, patience is key and check your work as you go.
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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.
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.
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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.
#14
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Machine shop - cheaper than a $250 tool
Machine shop - much higher quality than a $35 tool.
Machine shop - much higher quality than a $35 tool.