Fork steerer threads: cut or rolled?
 

A recent thread on this topic brought up the question as to whether fork steerer threads are cut or rolled. It got me wondering, so I contacted my local Columbus dealer (framebuildersupply.com) they contacted Columbus, and the answer:

They are cut. At least that's the way Columbus does it.

I've purchased steerers from Nova Cycles before, who contract to have their own made. They appear to be cut as well.

Others may roll theirs, but I've looked at a few 1" threaded steerers in my life, Ishiwata, Reynolds, True Temper all appear to have been cut. I say that because the ridges of the threads are sharp. I have a hard time trying to figure out how a rolled thread would have a sharp edge, but perhaps someone will pose some pix or links to convince me.

BTW, here's a video I found of an axial thread rolling machine in action. Pretty cool.

i just checked a few forks i had laying around. some are hard to tell, but one is very obviously cut as it was painted first and a bit sloppily, and the silver cut stands out against the paint at the bottom of the threading as quite obviously a cut. i guess one can also tell by using a magnifying glass: a cut thread will have tiny tears/fractures perpendicular to the thread-.

I've certainly refreshed old and cut new threads in several forks using a die, and the old threads looked cut to me.

Thanks for the answer.

All the steer tubes I've dealt with (Columbus, Reynolds, Ishiwata, Tange) have had cut threads. They're done very cleanly, probably on a lathe.

Thanks for looking into this. Now we know.

yes a steerer is threaded by cutting while a separate tube, before the fork is made.

Spoke thread is rolled in.

I would imagine that you'd need relatively mild steel to roll threads into a steerer. So it seems like less expensive bikes could have used rolling on their thicker steerer walls, like BMX with their smaller quill size.

Your timing is perfect, your analysis superb.

Separately I emailed Lon Kennedy at Nova Cycles, which is another framebuilder supply company. Here's his response just an hour ago:

"All of ours are cut and have never been rolled. I think for CrMo material rolling is not used. For mild steel where it is beneficial to take cheaper material and cold work it to a strength makes more sense."

I think I'll go home now, as I've filled my daily quote of learning a new thing.

Holy crap, Gugie, you did some actual research! What a concept! If we're not careful, this whole thing could turn into an intelligent and well-informed discussion.

What you heard from your various sources makes sense to me. I've never seen a steerer thread that appeared to be rolled, although I've mostly just looked at them in passing rather than subjecting them to any real scrutiny.

For what it's worth, when I asked Steve and Bilenky Cycle Works whether the threads on the replacement steerer he would be providing were cut or rolled, he replied:

"I have some factory original Reynolds and Tange threaded 1 1/8 steerers; threads are rolled. If they work for your head tube length, then we are in business."

What can that mean? Maybe Reynolds and Tange steerers do have rolled threads, while Columbus cuts the threads? Possibly, but that seems unlikely to me. I would guess that framebuilders are as prone to repeating the conventional wisdom as anyone else. He's probably just mistaken.

Another question remains unanswered, though: As SquidPuppet noted in that earlier thread, some people get really exercised at any suggestion that it's safe/reasonable to thread a threadless steerer. Casual measurement seems to suggest that both the OD and wall thickesses of the two are the same, but I still have some lingering doubts. Andrew Muzi at Yellow Jersey told me that you can in fact thread a threadless steerer, but that the diameter is slightly too small to get an ideal thread; he implied that the difference might be on the order of a few thousandths.

I don't have a selection of threaded and threadless forks handy to measure. Is there someone with an accurate digital micrometer and a stash of assorted threadless and threaded forks who would be willing to take some measurements and report back on their findings? It would be nice to either confirm that bit of folklore (that threadless steerers are ever-so-slightly-smaller-dimensioned than threaded ones), or knock it on the head for good.

I ride a 51cm, so when I came across an SR Prism fork out of a 60cm frame I was able to simply cut off the threaded section and use the fork with a threadless headset.

If Muzi is right that there are dimensional differences in the steerers, it certainly wasn't enough to prevent my CK headset from fitting and adjusting perfectly.

My threaded Fuji steel steerer is 1.000", my Bianchi threadless is .997" and my Kestrel EMS threaded is .998'. This would suggest there is more variation just in the threaded steerers than between threaded and unthreaded.

For what it's worth, the highly regarded Columbus steerers aren't terribly round, based on my small sample size and talking to a few framebuilders. The ones I get from Nova Cycle are very round - they spec their own tubing. That doesn't mean that Nova steerers make a better/stronger fork than Columbus, but it sure makes it a bit easier to build a fork. I need to use the file a bit for one, hardly at all for the other. Less Vitamin I at the end of the day...

To add a data point, some years back I had a new frameset with a threadless 1" fork and decided to have the fork threaded so that I could use a traditional quill stem. I found a frame builder to do that, and all was good, but, darn, that steerer was way tight for a 22.2 stem. I managed to get one in, but it took a lot of force. Yeah, I should have tried a French/22.0 stem.

Back to conjecture here, but I can't think of a good way to test this hypothesis: Possibly the confusion between cut and rolled threads on the part of some has to do with how they are cut. Threads that are created with a threading die in a bike shop are always seen as cut. But threads that are cut on a lathe in a manufacturing plant may be mistakenly seen as rolled rather than cut, because it's an industrial process that could be described as rolling, since the steerer is rotated as the threads are cut.

In other words, this could be analogous to the confusion about "sealed bearings." To some, it means a loose-ball bearing that includes some sort of rubber seal, while to others it means a cartridge bearing.

Maybe that just muddies the waters further, I don't know.

You would think the pile of metal shavings would be the obvious difference between cut and rolled.

True, but they don't typically ship the shavings with the tube set. :innocent:

That's just crazy talk!

Just piping up from the peanut gallery, there isn't much engineering reason to roll steerer threads anyway, right? The threads only need to hold the torque of the top nut, so they don't need to be exceptionally strong or deep into the metal of the steerer. I assume (but am always open to correction) that cutting is an easier/simpler method than rolling.

I wonder what would happen to a steer tube in a rolling machine like this one I think too that since the threaded portion of a steer tube is relatively short it doesn't make sense to roll a short amount, especially if using a mandrel is necessary with thin wall tubing. I also agree that the strength of rolled threads isn't really needed in a headset. The video also explains some of the reasons to use rolled threads and none of them really make sense for steer tubes.

From Lon Kennedy, above: "For mild steel where it is beneficial to take cheaper material and cold work it to a strength makes more sense"

I'd conjecture the main reason for rolling threads would be to make the threaded portion of the steer tube slightly stronger in case someone adjusts their quill stem too high. Of course that's not supposed to happen - but it does. A second possible reason might be because it's faster. I'm sure the tooling cost plays into it as well.

AFA a mandrel, yeah it would be needed, but you've got to assume tubing factories are mandrel equipped...

I seem to remember seeing rolled threads on old mid level mtbs and other bikes, but frankly it's been so long since I've worked in bike shops I can't say really. In the previous discussion I'd just assumed they'd be rolled because it's faster and stronger, but clearly that is not correct, at least for higher end steerers.

And what's really cool (to me) is that the company in the video you linked is here in Portland, OR. Besides bikes, they make a lot of stuff here still.

As a slight aside, if any of you have never seen a Phil Wood spoke thread roller in action, I think there's a youtube of it somewhere. Those contraptions always fascinated me in real life. Presumably DT spokes are made of something harder than mild steel. I don't know what SS alloy they use.


Here's one:

Nor do they ship the lathe Jon referred to.

I'd order a lot more steerers if it came with a punch card for a lathe - buy 100, get a lathe for free!