Cutting threads into a 1" threadless fork (steel steerer)?

[mhespenheide]

Can anyone advise on cutting threads into a fork that has a threadless steerer tube? It's a 1" steel steerer tube. I've read a lot of back-and-forth opinions in my online research. If you've personally done it or know of a machine shop/frame builder/wizard-level shop that does it, please comment on your experience(s).


Thanks!

[lovebird]

I've done it twice - absolutely no problem, except a little wear on the tool. I used the Park tool, which has a built in guide. The key is to go slowly, use a lot of cutting fluid, and obviously clear the die by reversing direction every 1/2 turn or so.

The Park die has an adjustable set screw. For the first pass, I set the die wide (I think that required tightening the set screw a fair amount), which has the effect of cutting the threads very shallow. A tighter, second pass did a nice job deepening them, and the headsets were very smooth and no issues tightening the bearing cap or nut.

It is a fair amount of work to cut the threads, so I would cut the steerer first to about 1/2" within final steerer length. You don't want to be cutting more threads at the top of the steerer than you need to. The extra 1/2" gives you a little room to play with when you first start cutting the threads (shallow), although I went slow and didn't need any room for mistakes. Maybe I was just lucky! Also, of course, be careful not to cut more threads than you need to on the bottom - just enough to allow the bearing nut to tighten down nicely onto the cup.

I have heard that cutting threads into a 1" threadless steerer could result in a weaker steerer than one in which the threads were rolled or which was specifically designed for threading (perhaps with a thicker wall?). I have to say I didn't notice that at all, and a standard threaded stem seemed to be a nice tight fit, so I am a little dubious that the wall thicknesses are different. Perhaps a framebuilder could chime in here.

I found that it is almost impossible to get a shop to do this, so you are probably on your own. Good luck! (PM if you want any more details.)

[Mark McM]

As noted above, it can be possible to thread a 1" threadless steel steerer - but only if the 1" threadless steerer has the same inner diameter as a threaded steerer (22.2 mm). The correct inner diameter is needed for two things: Adequate thickness so that the threaded portion retains enough strength; and so that a quill stem fits and clamps properly inside the steerer (quill stems rely on a specific steerer ID). Unfortunately, however, in the interest of weight savings, many steel threadless steerers use thinner wall thicknesses than is required for threading.

I actually have one 1" threadless steerer that had threads cut into it by the bike shop I bought it from. The shop had cut the steerer a little too short for my bike, so they 'saved' it by cutting threads into it for a threaded headset. Fortunately, this Rock Shox steerer had the same ID as a threaded steerer. But I've also got a couple of forks with 1" threadless steel steerers whose wall thicknesses would be far too thin to be threaded.

[zennmotion]

While it's possible, and I've done it (using a new Hozan cutter) I wouldn't be too cavalier about how easy it is. Park, Hozan, even Campy cutting tools aren't really designed to cut new threads, it's tricky to get the cutter to seat properly so the threads are correctly aligned perpendicular to the steer tube- I'd even say it's the luck of the draw for a newbie to get it right (my success was luck, not skill). The cutters are designed to clean existing threads, or extending threads, a much easier job. Cutting new threads requires a new, sharp tool and new sharp tools cut easily- increasing the possibility of misalignment. I think a shop might decline because of liability (how thick is that steer tube?) possibility of misalignment, and it's hell on expensive tools. I'd look for a framebuilder to do this, or accept the very possible risk that it doesn't go well DIY.

[mhespenheide]

I'd rather not do it myself. It's a great fork, and just about perfect for what I'm looking for. I'm hearing a lot of caution about zenmotion's point about getting the threads properly on-axis and I'd rather not mess it up and then have to commission another one built from scratch to my specs.

I'd prefer to have a local machine shop take it on, but I'm having a hard time to get them to answer my phone calls / emails -- perhaps it's too small a job and they don't think they can bill enough for it to be worth their time?

Alternately, I'm happy to mail it off to a framebuilder or master mechanic who's willing to take it on -- as long as the cost doesn't start to approach that of another (used?) fork.

There's a star nut in there right now, so I can't really fit a quill stem in more than ~4mm to check the fit, but it seems right. I'll borrow some digital calipers to see if the internal diameter is 22.2mm.

[lovebird]

Definitely not DIY job if you have any misgivings about taking it on. And of course the cautions about using a sharp tool are well-taken. But I found that it really was not very hard to avoid misalignment in the initial threads using the Park tool. It has a pretty tight cutting guide that locks in below the cutting die and makes it pretty tough to get the tool other than perpendicular. Take a look at the instructions here and you can see the guide: https://www.parktool.com/assets/doc/product/FTS-1_instructions.pdf. At least for one of the forks I threaded (a Zanconato) I didn't put the fork in a vise, just an old wheel clamped in and held between the legs was enough.

I know that the old Shaw's Cycles in Santa Clara (CA) was willing to cut new threads, but they closed more than 5 years ago. That was the only shop I knew that was willing to do this. I know that Jim Kish offers tool sharpening for fork dies. http://www.kishbike.com/services. Might be worth a call to see if cutting new threads is something he'd be willing to take on, and if he is willing you could be confident that you're going to get a top quality result.

[oldpotatoe]

Can anyone advise on cutting threads into a fork that has a threadless steerer tube? It's a 1" steel steerer tube. I've read a lot of back-and-forth opinions in my online research. If you've personally done it or know of a machine shop/frame builder/wizard-level shop that does it, please comment on your experience(s).


Thanks!

Use something to make sure the threads are cut parallel to the fork crown race, no problem. I've had it done 3 times on Merckx threadless forks..I'm riding one now on my MXLeader. Mine done by 'cranky franky, Frank Vogels, formerly of Maverick..not sure where he is now. For those above who said they have done it with standard shop thread cutting dies, huzzah..but it's really hard to get the threads parallel. And if they aren't the HS will be pretty near impossible to adjust.

[C40_guy]

Can anyone advise on cutting threads into a fork that has a threadless steerer tube? It's a 1" steel steerer tube. I've read a lot of back-and-forth opinions in my online research.
Thanks!

Given the potential downsides of getting it wrong...why not change the headset and stem?

[zennmotion]

I'm gonna guess, It's too short.

Or....given the timing and the OP location...

The old man tribe at Eroica can be brutal!:rolleyes:
In which case--

Look there's no rulez (rules, sorry) regarding threadless stems. And it seems to me, that dumbing back a modernish fork to look old doesn't neatly square with the spirit of the thing anyway. I say fly your freak flag, replace the headset and get a nice polished -17deg threadless stem in 26.0 (Velo Orange has a nice one for not much money).

PS star nuts can be removed gorilla style by a broom handle, just push it through the bottom. It can probably even be reused if you aren't too brutal with it.

[C40_guy]

I'm gonna guess, It's too short.



Hmm. I have one of those, but it's carbon. :(

Note to self. Measure twice. Then add the height of the stem. Measure again. Step away from the bench. Come back. Measure one more time. Recheck that I've added in the height of the stem. Then cut.

D'oh!

[mhespenheide]

Given the potential downsides of getting it wrong...why not change the headset and stem?

That's certainly the backup plan!

But zenmotion is kinda right, too -- the fork's going on an '87 Bianchi, which was my first good bike that I raced on back in the day for junior USCF and collegiate racing . I've got a titanium quill stem from ITM that I'd like to run on it, and I'd like to keep the bike semi-period correct to how it was back then. Or, more accurately, authentic to my memory of who I was (and what I lusted after) at the time. And yes, I plan to ride it in Eroica California some day -- probably not this year -- where I will annoy plenty of the old man tribe with different equipment tweaks.

As I said in another thread, it's a quixotic/neurotic quest that I fully acknowledge is not 100% reasonable.

[zennmotion]

As I said in another thread, it's a quixotic/neurotic quest that I fully acknowledge is not 100% reasonable.

Understood, should just said that in the first place! I salute you! :hello: Go find a F-builder with a lathe, there's a few in here...