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Fork conversion from threadless to threaded?

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Fork conversion from threadless to threaded?

Old 03-14-18, 05:20 PM
  #51  
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Originally Posted by wesmamyke View Post
I think the biggest issue with threading an unthreaded steerer is getting the die started straight. If you want to experiment a guy has a couple 1-1/8" threading dies on ebay super cheap right now, no pilots or handle though. It's heresy to talk about threading a threadless fork, but if it was mine I'd probably just try anyway.

Went and measured the longest 1-1/8" threaded steerer I personally have, about 8.5" and that's the longest non replacement fork I've ever seen. The frame it came off was gigantic by mountain bike standards, 23" or 24" at least.
Okay, tomorrow I'm actually going to go measure my head tube and steerer. We got about 18 inches of snow last night, so it's a slog getting out to the shed. One of these years I will remember not to store my snowshoes in the shed.
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Old 03-14-18, 06:45 PM
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Originally Posted by Trevtassie View Post
I've never measured one, it's just what I remember being told, and took it as gospel....
Originally Posted by himespau View Post
same here as I've been told this over and over.
I remember someone in a previous thread pointing out one certain manufacturer that received an inquiry about threading one of their threadless forks. They advised against it, stating that their steerers were thinner and wouldn't tolerate the process. I can't remember the brand though. Ah...... found it. Surly.

No! Don't do it. Really, just don't; It's unsafe. The wall thickness of our forks' steer tubes is too thin to thread safely, and as well as the inside diameter won't be right for your quill stem.
I was going to make a 1-1/8" threaded bike a few years ago. I already had a threadless fork and the wall thickness was 1/16". Same as a one inch threaded fork, same as a 1-1/8" threaded fork. I got into some interesting debates on the subject here. Most folks saying that it was a bad idea. Since then, curiosity has caused me to measure every 1-1/8" threadless fork that crosses my path. So far they've all been the same. 1-1/8" OD and 1" ID.
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Old 03-14-18, 06:56 PM
  #53  
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Originally Posted by SquidPuppet View Post
I remember someone in a previous thread pointing out one certain manufacturer that received an inquiry about threading one of their threadless forks. They advised against it, stating that their steerers were thinner and wouldn't tolerate the process. I can't remember the brand though. Ah...... found it. Surly.

I was going to make a 1-1/8" threaded bike a few years ago. I already had a threadless fork and the wall thickness was 1/16". Same as a one inch threaded fork, same as a 1-1/8" threaded fork. I got into some interesting debates on the subject here. Most folks saying that it was a bad idea. Since then, curiosity has caused me to measure every 1-1/8" threadless fork that crosses my path. So far they've all been the same. 1-1/8" OD and 1" ID.
That's really interesting. I can see it from Surly's point of view--they have no control over how people are going to thread their forks. If they start the die off-center, they're going to end up cutting way into the steerer once they've threaded any distance. Then when the steerer breaks a the base of the threads, here comes a big lawsuit.

Tempting to try it, though. I haven't looked into it, but it's presumably not rocket science to align a threading die correctly.
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Old 03-14-18, 07:19 PM
  #54  
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Originally Posted by wesmamyke View Post
I think the biggest issue with threading an unthreaded steerer is getting the die started straight.
This was part of a big debate here a couple years ago. Most folks stated that Park Tool's kit was for chasing only and definitely not meant to cut new threads. Especially on a steerer with no existing threads. They were adamant that cutting new threads was a huge risk, almost impossible, that the walls were too thin, and getting the die started straight was a near impossible task.

I pointed out that I have done this myself. I was told that I was a full of **** liar and it was obvious by my tone that I didn't have clue what I was talking about. I provided links to Park Tools instructions on how to use their threading tool to cut new threads on 100% unthreaded steerers. In fact, Park's instruction begin with cutting a naked steerer and end with chasing. I also provided links to Parks instructions on how to use their die GUIDE that is specifically designed to achieve a straight start on an UNthreaded steerer. A lot of poster got really nasty, saying that only an idiot would attempt such a project since the tools weren't meant for the task.

I never understood that.

Park makes a 1-1/8" die. (why? If not for cutting threads?)
They make a guide for getting a straight start.
Wall thickness on a threaded steerer is 1/16"
Wall thickness on a threadless steerer is 1/16"

Threading Procedure

When adding new threads to uncut column, it is important the die be fully opened. This will take a minimal cut of material. The die must be adjusted and again used to cut more thread depth. The process is repeated three to four times until the diameter is reduced enough to thread on the headset.
Place FTS-1 onto fork column (figure 8). Guide will align die and handle square to steering column.igure 8. Handle and die are held aligned to column by use of the guide
Even the photos are of an uncut steerer.

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Old 03-14-18, 09:05 PM
  #55  
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I was just thinking about how the dies are adjustable, makes sense to do it in a couple passes.

Seems like you could do it on a lathe pretty easy too, that's a thing right? Lathes setup just for threading things?
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Old 03-15-18, 05:51 AM
  #56  
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Originally Posted by SquidPuppet View Post
This was part of a big debate here a couple years ago. Most folks stated that Park Tool's kit was for chasing only and definitely not meant to cut new threads. Especially on a steerer with no existing threads. They were adamant that cutting new threads was a huge risk, almost impossible, that the walls were too thin, and getting the die started straight was a near impossible task.

I pointed out that I have done this myself. I was told that I was a full of **** liar and it was obvious by my tone that I didn't have clue what I was talking about. I provided links to Park Tools instructions on how to use their threading tool to cut new threads on 100% unthreaded steerers. In fact, Park's instruction begin with cutting a naked steerer and end with chasing. I also provided links to Parks instructions on how to use their die GUIDE that is specifically designed to achieve a straight start on an UNthreaded steerer. A lot of poster got really nasty, saying that only an idiot would attempt such a project since the tools weren't meant for the task.

I never understood that.

Park makes a 1-1/8" die. (why? If not for cutting threads?)
They make a guide for getting a straight start.
Wall thickness on a threaded steerer is 1/16"
Wall thickness on a threadless steerer is 1/16"





Even the photos are of an uncut steerer.

I had just read the same info on the Park site and came to the same conclusion that you did. I'm going to ask some experienced frame builders what they think of the idea, but at this point it seems likely to me that there's no difference between the tubing used for either type of steerer.

I was sorry to hear that a previous discussion on the subject got ugly and personal. Was that on C&V? We're usually so polite around here. That's one reason that this is pretty much the only forum I use. From what little I've seen, the Mechanics forum seems to have more than its share of didactic and angry people. Screw 'em.
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Old 03-15-18, 10:49 AM
  #57  
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Originally Posted by jonwvara View Post
I had just read the same info on the Park site and came to the same conclusion that you did. I'm going to ask some experienced frame builders what they think of the idea, but at this point it seems likely to me that there's no difference between the tubing used for either type of steerer.

I was sorry to hear that a previous discussion on the subject got ugly and personal. Was that on C&V? We're usually so polite around here. That's one reason that this is pretty much the only forum I use. From what little I've seen, the Mechanics forum seems to have more than its share of didactic and angry people. Screw 'em.
No, no, not in C&V. In the mechanics forum. The folks here in C&V seem to thrive on learning and sharing.

If you think about it, the choice of wall thickness was probably arrived at/determined by what will support a rider's weight and survive the duties and abuse of riding, + some margin of overbuild.

The strange part was that many (a LOT) of the people advising against it were shop mechanics and/or owners. When I asked why it shouldn't be done if the wall thickness was the same, I literally got answers like, "They are not designed to be threaded". Which of course led me to and then to ask, "In what way?". So you can guess where that went. It appeared to them that I was questioning their authority and wisdom, rather than asking a question about metal tubing.

So, of course, I lowered my standards and started being a snarky punk.

Anyway, you could probably get a fork from a totaled bike at your local co-op or maybe even the LBS, for pennies. You could take a few practice passes. You could even cutoff the threads and make additional practice starts if you felt the need to polish your technique.

Good luck, on either route you choose to take.

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Old 03-15-18, 11:04 AM
  #58  
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Originally Posted by jonwvara View Post
I had just read the same info on the Park site and came to the same conclusion that you did. I'm going to ask some experienced frame builders what they think of the idea, but at this point it seems likely to me that there's no difference between the tubing used for either type of steerer.
It's likely, but I wouldn't assume it is.

Obviously the OD of all 1⅛" threadless steerers is the same, because the ID doesn't matter to a threadless system. But just as obviously, the ID matters when you intend to use a quill stem. Since it's possible to make a 1⅛" threadless steerer thicker or thinner than a threaded one, I'd make sure the ID is within spec. IOW, measure it. A too-thin wall will make for a pretty risky threading operation. A too-thick wall will make getting that stem in pretty difficult.

FWIW, I've seen 1" threadless steerer tubes that have a thicker wall that would preclude using a quill stem unless it was French OD of 22.0mm. Even then the fit was tight.
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Old 03-15-18, 11:17 AM
  #59  
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A few years ago I found that many bike shops refuse to cut additional threads on a steerer, much less threads on an unthreaded steerer. The reasoning was that they believed it dulled the cutter, and most of them only used it to chase already cut threads. I did find one shop that would do it for $25/inch of threads. I thought this was a reasonable price.

So, for the OP, perhaps the best bet would be to cut the unthreaded steerer to a "well measured" final length. This would be head tube length + headset stack height, including washers. Once done, cut threads as @SquidPuppet shows.

If you want to keep the current fork, that would appear to be your best bet.
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Old 03-15-18, 11:30 AM
  #60  
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Is there a safe shim that would allow OP to use 1" quill stems after threading, or, after all this, will he be limited to using 1 1/8" quill stems, which, to my understanding, are not all that common in high quality?
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Old 03-15-18, 11:33 AM
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Originally Posted by jonwvara View Post
I'm going to ask some experienced frame builders what they think of the idea, but at this point it seems likely to me that there's no difference between the tubing used for either type of steerer.
I'm not claiming to be an experienced frame builder, but I am an engineer, and I can read a spec.

Here's the Columbus spec for threadless

1.55mm wall thickness on non-butted (top of the steerer) end.

Here's the Columbus spec for threaded

1.55mm wall thickness on threaded end.

Drawing on my several semesters of mathematics, I contend that A=B. My engineering training leads me to conclude that one can thread a threadless steerer. My LBS and framebuilding experience leads me to believe you should find someone that is competent and experienced in performing this task.

Edit: somewhere along the way I forgot that the OP has a 1-1/8" steerer. My answer remains the same, Columbus spec is 1.55mm wall thickness as well. I'm fairly certain the ID on 1-1/8" steerers is consistent, otherwise you'd find various size star washers, no?
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Old 03-15-18, 11:56 AM
  #62  
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The main thing to be careful of IMO is cutting the threads too far down the steer tube. If the expander wedge of the stem is pressing against the threaded portion of the steer tube, it will eventually cause a failure. Maybe you'd get away with it for a while, but it's a Bad idea to take the risk. Threading your own tube in a way is an advantage, as you only have to thread as much as you need to engage the headset top nut and cup.

Also, FWIW, I was always taught that rolled threads are stronger than cut threads. Steer tube threads in a factory are rolled on a lathe. Rolling dies don't remove any material. Cutting dies like the Park do. I'm not an engineer. If any of you have any comments on that I'd love to hear them. Just thought it was worth a mention.
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Old 03-15-18, 12:00 PM
  #63  
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Originally Posted by himespau View Post
Is there a safe shim that would allow OP to use 1" quill stems after threading, or, after all this, will he be limited to using 1 1/8" quill stems, which, to my understanding, are not all that common in high quality?
Yes there are good, safe shims available. But unlike a few years ago, I've discovered what seems to be a mild resurgence in availability of 1-1/8" quill stems. Some with removable face plates, some with traditional styling offered by the inexpensive (but still quality) brands, and even this fine specimen.


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Old 03-15-18, 12:01 PM
  #64  
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Way back there was an MTB frame builder shop in the woods of southern Oregon, they made a double wedge quill ,

and a stem, that the upper wedge expanded into, So you could pull the stem quill out of it,

did not need cable/housing slack to allow the whole stem to come up high enough to clear the top of the steerer..

A certain Rinko/Tour bike Packing advantage to that scheme.. now a custom build..





...
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Old 03-15-18, 12:13 PM
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Originally Posted by Salamandrine View Post
Also, FWIW, I was always taught that rolled threads are stronger than cut threads. Steer tube threads in a factory are rolled on a lathe. Rolling dies don't remove any material. Cutting dies like the Park do. I'm not an engineer. If any of you have any comments on that I'd love to hear them. Just thought it was worth a mention.
Here is my non qualified opinion on that. All the important stress, fatigue, and torture occur where the steerer joins the crown. That union needs to be STRONG. The threads at the top allow the top race to be positioned (not tightened) to set proper bearing preload, and a lock nut to be gently snugged, simply to prevent the race from coming out of adjustment. That's it. There is no top-to-bottom tension on the steerer, or the threads. Gravity and rider/bike weight hold it all together.
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Old 03-15-18, 12:35 PM
  #66  
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I've had some Giant MB bikes with long head tubes, threaded 1 1/8. Maybe a trip to the co-op might find you something.
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Old 03-15-18, 12:38 PM
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Originally Posted by SquidPuppet View Post
Here is my non qualified opinion on that. All the important stress, fatigue, and torture occur where the steerer joins the crown. That union needs to be STRONG. The threads at the top allow the top race to be positioned (not tightened) to set proper bearing preload, and a lock nut to be gently snugged, simply to prevent the race from coming out of adjustment. That's it. There is no top-to-bottom tension on the steerer, or the threads. Gravity and rider/bike weight hold it all together.
Yeah that's true. The crown race and the bottom cup pretty much take all the load. Top is there for centering.

There would be some top to bottom tension induced by side load wedging action across the ~conical races. One could argue it's incidental, but it's not zero. Never thought of this till right now, but it would seem that this effect might be minimized in headsets because both cups and both 'cones' face the same direction. They are not mirror imaged as they are in hubs and BBs. So a side load won't have as much tendency to wedge them apart. Someone must have figured that out like 130 years ago...
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Old 03-15-18, 12:41 PM
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Back OT, wouldn't it be easier just to get one of those adjustable threadless stems and call it a day?

I can sort of envision sewing a little canvas covering for it, to hide the ugliness and make it look quasi retro. Leave a hole for the allen wrench. Add some twine and shellac as needed.
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Old 03-15-18, 12:57 PM
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Originally Posted by Salamandrine View Post
Also, FWIW, I was always taught that rolled threads are stronger than cut threads. Steer tube threads in a factory are rolled on a lathe. Rolling dies don't remove any material. Cutting dies like the Park do. I'm not an engineer. If any of you have any comments on that I'd love to hear them. Just thought it was worth a mention.
I don't think this is correct. The forks I have obviously have cut threads, the OD is just slightly less than the unthreaded portion of the steer tube. Rolled threads have an OD slightly greater than the unthreaded portion, such as on spokes.
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Old 03-15-18, 01:03 PM
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Originally Posted by Paramount1973 View Post
I don't think this is correct. The forks I have obviously have cut threads, the OD is just slightly less than the unthreaded portion of the steer tube. Rolled threads have an OD slightly greater than the unthreaded portion, such as on spokes.
Could be. Anyone know for sure? Are both methods used?
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Old 03-15-18, 03:10 PM
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Originally Posted by Salamandrine View Post
Could be. Anyone know for sure? Are both methods used?
I always assumed that for mass production the threads were cut on a lathe. But cut, not rolled. I'd like to know the actual scoop too.
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Old 03-15-18, 04:46 PM
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Originally Posted by Salamandrine View Post

Also, FWIW, I was always taught that rolled threads are stronger than cut threads. Steer tube threads in a factory are rolled on a lathe. Rolling dies don't remove any material. Cutting dies like the Park do. I'm not an engineer. If any of you have any comments on that I'd love to hear them. Just thought it was worth a mention.
I have heard that stem fork-column threads are rolled, not cut. In fact, I just got an email from Andrew Muzi saying the same thing (I had emailed him to ask if their shop would thread a threadless fork for me, since they seem to do a lot of frame repairs.)

Maybe he's right. But if

A) some steerer threads are rolled (those that originate at the factory), and

B) others are cut (threads that are cut with the Park fork die and guide, for example), and

C) the OD of the unthreaded tubing is the same in either case, it would then seem to follow that

D) threaded sections have got to be different diameters, yes?

But if D is true, how come all threaded headsets of a given size (1", say, or 1 1/8") fits any threaded steerer of the same size designation? Wouldn't there have to be two versions--a rolled-thread version and a slightly smaller cut-thread version?

That makes no sense to me. I'm prepared to believe that all threads are rolled, or all threads are cut, but not that some are cut and some are rolled.

Does anyone have an explanation for this?
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Last edited by jonwvara; 03-15-18 at 04:51 PM.
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Old 03-15-18, 05:17 PM
  #73  
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I'm not sure about rolled vs cut, but I do know that rolled will be stronger, as the material grain structure is different for rolled.
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Old 03-15-18, 08:00 PM
  #74  
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Rolling threads on thinwall tubing? Invites tubing distortion, might require mandrel?

Anyway I suspect the standard headset thread diameter is simply large enough to engage either rolled or cut steerer threads.
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Old 03-15-18, 09:39 PM
  #75  
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Originally Posted by jyl View Post
Rolling threads on thinwall tubing? Invites tubing distortion, might require mandrel?

Anyway I suspect the standard headset thread diameter is simply large enough to engage either rolled or cut steerer threads.
Then wouldn't the races and locknuts fit really sloppily on the cut threads? Sloppy enough to cause issues?
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