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Steerer tube replacement on '44 Rollfast

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Steerer tube replacement on '44 Rollfast

Old 03-18-24, 10:38 AM
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Steerer tube replacement on '44 Rollfast

Got this helpful reply from Iride01, So I took his advice and came here:
I can't tell you about replacing it entirely. That might be more for a question in theFramebuilderssub-forum. I don't think many do that as a normal thing.

But since you are likely talking about a steel steerer tube, then cut it off at least a inch or so below where ever a quill stem might get too. And far enough away from the fork crown that the heat of brazing doesn't bother it.

Then braze on another piece of steerer tube of the same ID and OD with a internal union that is at least a half inch into each section of the joined tubes. Then dress up the outside with a file or something to bring the brazed joint back to the OD spec.
I wondered why a heating the original brazed joint and pulling the damaged tube out wouldn't be easier and the subsequent fix stronger.
My original search on this was disappointing, but I'm still learning how to navigate here.
Thanks for any ideas, Steve
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Old 03-18-24, 01:13 PM
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Can you post a picture of the steerer/crown? I personally feel more comfortable replacing the entire steerer. But given the bike, I'm wondering if it's a standard steerer.

We have talked about steerer replacements or patching before in here, I recall at least one thread not long ago. Searching might be difficult though. Sometimes google search is a better way to find content on bikeforums.
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Old 03-18-24, 04:11 PM
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Do you know the stem diameter? Lots of older American bikes have an undersized stem, 0.833" instead of the more standard .875" (7/8")
Assuming you want a proper restoration, you might want to source the thicker-walled steerer that fits your undersized stem.

Both the "splice" method and the total-replacement method have been done plenty of times and can be safe and reliable if done well. Don't give it to someone who's never done one, there are enough experienced folks out there.

Personally I would not "sweat" (melt) the steerer out, too many unknowns. Like if they pinned it or tack-welded it and you don't know that, you can keep heating and heating until the crown is ruined and the steerer still hasn't budged. Safer to bore the crown to diamater on a mill or a lathe. Advantages: done cold so no more heat damage to the crown, and it doesn't care if the original was pinned or spot-welded. Disadvantage is it takes longer, mostly in the setup. A dedicated fixture is best, but building one will normally cost as much as buying a new fork. Maybe your repair guy has one already or wants to have this kind of fixture for future repairs, so you won't have to pay the full cost of making it. I have "planned" (dreamed of) to make one for something like 40 years now and haven't got around to it, just waiting for a fork that I care enough about to make it worth my time. I'm not offering to do it; I won't work on someone else's fork without product liability insurance. Maybe someday.
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Old 03-18-24, 06:28 PM
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Mark, have you ever seen a picture of someone's steerer boring setup on a lathe? I suppose it's a lot like the fixtures people make to miter unicrown fork blades. I'll have to think about it.
I want to replace a steerer where I munged the threads at a bad place, right under where the threaded headset cup would go. Seems like it could be an annoyance for the life of the fork if I don't get rid of it. Or maybe I could fill it in with brass and thread it again.
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Old 03-18-24, 07:02 PM
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Originally Posted by unterhausen
Mark, have you ever seen a picture of someone's steerer boring setup on a lathe? I suppose it's a lot like the fixtures people make to miter unicrown fork blades.
No haven't seen one, that I can recall, but yeah about the same as for unicrown mitering. The same fixture could be used for both. Hold the dropouts, and the blades up near the crown. Bolt it to the cross slide somehow that lets you ensure it's parallel to the spindle, maybe with a center hole where you can stick a center mounted on the tailstock.

It'll need a height adjustment at the dropout end for the rake, and one at the crown end, though maybe just shimmimg there. Not much range of height adjustment needed since blades don't vary in size all that much. I figger I'd make it from 80/20, since you can bolt it together from off-the-shelf parts in minutes, no need to mill T-slots.
I want to replace a steerer where I munged the threads at a bad place, right under where the threaded headset cup would go. Seems like it could be an annoyance for the life of the fork if I don't get rid of it. Or maybe I could fill it in with brass and thread it again.
Filling with brass (or nickel-silver if you're concerned about strength) and re-cutting threads seems like a ton less work, and almost certainly good enough to last "forever". I'd try that for sure, because if it doesn't work, you can still replace the steerer.
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