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Stokeless Asshat
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Discussion Starter · #1 ·
I have a late 80's steel MTB fork with a threadless steer tube that I'm interested in converting back to threaded. I think I already know the answer to the "can I have threads cut" question....no. Correct me if I'm wrong there.

So this brings up the extending the steer tube questions. Would cutting it down to the needed length, sleeving with a 7/8" piece of chromoly and brazing on a donor threaded portion be a safe and viable option? Insertion depths? Would you go brass or silver? < Gap dependent?

This is a high quality fork on a bike that will be ridden.

Thanks,
Jeff
 

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Well, you could get a high quality tap and die set and try to thread it yourself, but I don't know how well that would work. I don't know if the steerer is too hard to cut a good and even thread. I don't know that welding a threaded piece is the way to go either. Aren't welds the weak point? Certainly the weld would be hidden in the head tube, but would the stem put stress on the weld causing it to crack or break? Is there no other option? Would it be possible to find a frame builder who still makes threaded forks to do this for you? Perhaps try to get lucky and find a threaded fork that would work? I do know that if this project doesn't go as planned you will be out a high quality fork that would appear to be very difficult to replace. In any case, I'm curious. subscribed.
 

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You might be able to thread it if the wall on the tube is thick enough and you can find a 1 1/8 die (maybe easy, maybe hard - that's something that will be really cheap if you can find it but finding it is the tricky bit). I'd look at that first. If it's that old the wall thickness is probably 1.5-1.8mm or something which should be enough to be safe IMO.

-Walt
 

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I am with Walt, your LBS would be a source for a die.

In earlier days of 1" steerers, it was not in common to do this task of re-threading, especially when a replacement was required for a short head tubed frame and the fork had a long unthreaded section.

I have also added length to a short steerer tube but I had a stepped extension made so only one side was brazed in. I never had any trouble with it.

Eric
 

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Stokeless Asshat
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Discussion Starter · #6 ·
I have a few great LBS's around here and most, even the old timers, really don't want to tackle cutting fresh threads. The wall thickness will handle it so if I can find a set of quality dies for less than 150.00 I'll jump on it and give it a go myself. It seems to me though that brazing in a sleeve would work. 4" sleeve, 2'' insertion, vent holes in the steerer to add filler, silver for flow and low heat.

Rody's technique is over my tool and skill set but as usual he gives great info.

Thanks again,
 

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Stokeless Asshat
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Discussion Starter · #11 ·
Yep. I've seen that a few times. Great info but like I said his method is out of my skill and tool set. I'm still not sure why no one is hot for the sleeve/braze technique. I see it no different than lugged construction with more overlap. What am I missing here? :)
That aside, I just picked up a park FTS1 for .50 over my budget so that will be my first route.
 

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I have sleeved and brazed a couple of steel fork steerer extensions for my own personal use, seems to me that the sleeved section is likely stronger than the original steer tube, I still have all my teeth. You can cut then ends of the sleeve at an 45 degree angle (much like a lug) in to spread the stress if the transition over a longer length of the steerer, make it less likely to stress crack.
If you are willing to permanently intrap the crown race on the fork, you could install the race first and instead braze an external sleeve over the extension joint. An external sleeve with accesable shorelines would be a bit easier to evenly flow the braze into and would leave the interior of the steerer unobstructed for the stem quill if that is a concern, downside is that it would then be impossible to ever replace the crown race!
 
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