Replacing threaded steel steerer with threadless?
 

I have a 1" threaded fork for a steel DeBernardi frame I'm contemplating rehabbing and putting back on the road. The topmost ~1/4" of steerer thread is semi-flattened, to the point that the headset lockring doesn't bite anymore, so the headset won't stay tight. I'm not wild about threaded in any case - I much prefer threadless for its simplicity and ease of setup.
The question: is it possible, or even advisable, to either replace the threaded steerer with a threadless one - either in its entirety by installing a new steerer tube into the crown, or by cutting down the threaded steered and "grafting on" a section of 1" threadless steerer tube? Is it possible to melt the brazing holding the steerer into the crown without compromising the fork leg/crown joints? Or should I bite the bullet and simply buy a new fork? Thoughts?

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You can replace the whole steerer, but an easier fix is to cut maybe half that steerer off and splice on a new top half, however much longer you want.

Doesn't even hurt the paint. The trick is finding someone willing to do it for you. I don't know for sure of anyone but maybe someone here does. Bernie Mikkelsen used to do a few of those, is he still taking in work like that? You could ask.

Obviously this is a very safety-critical component, so I might want to stay away from someone who's trying it for the first time. A track record is recommended.

This topic, replacing or extending steerers, comes up every so often here. I suspect there's a lot of posts for the searching.

Mark's suggestion of only replacing the upper section is a good one. With threadless there's no issue of quill stem insertion and steerer IDs. So an internal sleeve (if you braze and not weld) would be a fine method to splice the two parts together.

Were you to choose to remove the steerer completely I would not use heat to do this. The fork is most likely brassed/bronzed together and the remelt heat level is a bit higher than the original joining needed and this level needs to be held over the complete joint, for as long as it takes to pull the steerer out. Think of a couple of flames or a really big rosebud tip and gas supply. If there's any pins (nails) that were used to hold the assembly together while joining these will need to be found and drilled out first.

I've recycled a couple of crowns when i was younger and even with a silvered steerer it takes a bunch of heat and time. Andy

Thanks Folks - to me, the "grafting a threadless section onto a threaded stub" approach made the most sense, but I wasn't sure if it was a legitimate and/or advisable means of converting the fork. Apparently I can suggest it to a frame builder without being chased out of the room!

A little off topic but not entirely and there might be some wisdom here. I had my first Ti Cycles built with a 1" threadless steerer. Threadless being the Ti Cycles default and there was enough other stuff going on with the design that I didn't take it further. (My first threadless.) Well, the work and parts are all very good but I have not yet fallen in love with threadless. Looks to little for me and it is so much faster and easier to adjust stem height to dial in fit for that day with a quill. (And a nice Pearl would look good!) I've talked to Dave Levy about cutting down the steerer and threading it. He sees no issues there.

2nd issue - the bike has speed wobble. Always there but when I was younger, stronger and more confident, not an issue. I hit 50 mph early on, close to as fast as I've ever gone. But now, much over 40 is not fun at all. So a thought I just had - would the quill have any benefit at slowing speed wobble by slightly stiffening the steerer in the middle section rather than bending it at the top? And would a stiffer steel stem perhaps improve that again?

If he hasn't heard of it, Paul Brodie has a Youtube about his way of doing it: Though I'm not sure I'd have someone do it who has to watch a YT to learn how.

Personally, since I'm better at brazing than welding, I have done it with 56% silver, with a close-fitting sleeve inside. Internal taper at the top and bottom of the sleeve if time and budget allows it. Tapering the sleeve is probably not necessary, but it is Best Practice to minimize the stress-riser where the section thickness changes abruptly at the edge of the sleeve. Steerers are pretty thick though, as bike frame tubes go, and not much force on them there near the middle where the splice goes. High stesses on the steerer are mostly just above the crown, and to a lesser extent near the top from the leverage you apply to the handlebars.

I think the TIG welded splice with no sleeve inside is a proven method, if done carefully by a really good welder.

I'm thinking about replacing the entire steerer on a fork I made in about '88 for myself. I would like a longer steerer to get the bars up higher (also extending the head tube in the process), because I was a racer with a very aero position back then and now I'm fat and inflexible. The reason for not splicing: I used an unbutted steerer. It is Excell, a "super steel" almost twice as strong as 531 (~200 ksi IIRC), so maybe it's strong enough as-is, but another thing that's changed about me is I'm much less willing to fall on my face these days... And being fat, it's stupid to be a weight-weenie anywhere on the bike, much less on a steerer. Just thinking about it breaking takes all the fun out of high-speed downhilling.

I won't melt the steerer out though, because of the damage that does to the crown and maybe even the blades, which are silver-brazed to the crown (steerer is brass-brazed — contrary to my usual approach of brazing the whole crown in one heat cycle). I lightened the crown, after it was brazed to the steerer, using the steerer to hold it in the lathe and mill. I'm still confident the crown is strong enough, but maybe not with so much strength to spare that I can cook the hell out of it. And melting the brass while not melting the nearby silver is too risky.

So if I do this, I will bore the old steerer out, cold. This will require making a fixture to go on the lathe. Similar to a fork-brazing jig, only it won't hold the steerer (obviously), it will hold only the dropouts and the crown. I will dial it in until the steerer is exactly on the centerline of the lathe spindle, and use a boring head to precisely make the hole fit the new steerer, with silver-brazing clearance.

I wouldn't normally make such a fixture for a single use, but once made, it would allow me to do this repair on other forks easily in the future. Making the jig will take me maybe 2-3 hours, and since it's hobby time for me, it doesn't have to make sense dollar-wise. My fixture will be ugly, probably made of scrap metal, but rigid and with the ability to be indicated-in precisely on the lathe.

If anyone has a fork they want me to do this on, don't hold your breath! I have "been thinking about doing this" for at least 10 years, probably 20. There are lots of other projects in the queue before it, and those aren't happening very fast either.

Just throwing this out there in case anyone has any comments or suggestions... or has that exact fixture they could lend me!

I thought about this for a long time, but I was never happy with fixturing the fork. There's a reason why fork fixtures cost $1000. Call me crazy*, but I decided to spin the fork. Chuck up the steerer, make sure it has minimal runout, and drill out the steerer. The fork will be left sitting on the drill bit. There will be a speed transition, but I would do it pretty slowly anyway.

I was thinking about replacing a steerer, and I priced an MT3 extender and 1" drill bit. I probably would want to sneak up on the size, so a smaller drill bit would probably be a good idea. So it turned into a relatively expensive proposition in comparison to just buying another steerer and crown. I suppose if I had a irreplaceable vintage fork I'd probably go through with it. I have also thought that leaving a very thin cylinder of the steerer would be fairly easy to remove and the drilling operation wouldn't have to be perfect. I guess if you want to sneak up on the final size with different drill bits, doing it this way would be superior to spinning the fork where the steerer might be too thin to support drilling.

For the faint of heart, I have an angle plate that attaches to my lathe cross slide. I'm pretty sure a working machinist that knew OSHA was watching and wanted to do this job would clamp the fork on the angle plate and drill it that way. Probably cut off the steerer at the crown after indicating in the steerer. It occurs to me that Columbus's rifling would make indicating on the inside of the steerer impossible. It makes me laugh they are still doing that.

*People always think spinning the fork is crazy. Never had any problems with it. Consider this bad advice.

I don't think that would work for my fork, because it has a divot in front for the tire clearance, like some track forks.


That would make the drill wander towards the front of the crown. Even a drill that large is flexible, especially with that much stickout. Also drills don't make holes that are particularly round, or to dimension. I could see doing it with with a solid-carbide boring bar, but for one that large diameter and longer than the forkblades to reach the crown, I'd have to mortgage the house.

My fork-brazing fixture was free because it was given to me (thanks Alex!!) but I think they'd never cost more than a couple hundred if I had to buy everything. Anyone know what a Wetmore jig costs to make? A few pieces of 80/20 extrusion and some fasteners, a dummy axle and a little machining. Not the greatest fork jig but more than adequate for a hobbyist.


Anyway the fixture I envision for the lathe would be much cheaper, since I have enough scrap steel to make it, have a dummy axle etc, so it's just my labor, which is worth nothing!

Yes that is my plan. I'd clamp the crown to my fixture with the steerer held in a 5C collet in the spindle, shimming the crown until the fixture and collet "agree" with the fork clamped tight. Then cut off the steerer at the crown top, probably leaving just a bit of steerer as a visual doublecheck that I'm boring on the same center. If it's off, I would have a few mm to notice and correct before entering the crown hole.

The other end of the fixture with the dummy axle would have a center hole drilled in it and held precisely on-center by a dead-center in the tailstock, at least for the starting position, tho of course once I start feeding the whole shebang towards the boring bar, the tail support would go away. The tail center would just be for the initial setup.

Agreed on how dumb that rifling is. As John Oliver likes to say, "how is this still a thing?"

I got no problem with spinning a fork though. That's how I cut crown race seats. The Campy-style cutter is for people who don't have lathes. I pity them! ;)

A long enough boring bar would be ridiculously expensive, although maybe you can get an extension for those too. 1" or 1 1/8" is a little on the small side for a long boring bar.

I think the part that would cost on the fork fixture Alex made is the dummy axle holder. If someone has a mill, that wouldn't cost much, but otherwise it would probably cost as much as the rest of it. Depending on what you had the plates made out of, I'm guessing one of the online laser cutting places would charge about $100. Not sure what 80/20 charges. So $200 is about right. An angle plate like I have is about $50 if you catch them on sale.

Dale Saso in San Jose CA does threaded→threadless conversions. He did one on my Waterford and it has been great. He cut the existing steerer up near the threads and grafted on a threadless extension. He was careful with heat and kept the paint pristine at the fork crown.

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