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Old 06-25-07, 06:11 PM   #1
urbanknight
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How hard to extend threads on fork?

I think I finally found a fork with the correct specs for my bike, but it came off a 61cm bike while mine is a 55cm so the steerer is about 7cm too long. I know a shop nearby that can extend the thread for me, but is it asking too much to have them thread that far down?
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Old 06-25-07, 06:20 PM   #2
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hmmmmmmmm is this for the compression bolt?

why dont you just star nut that motha

if the thread is on the out side of the steer tube for those type of head sets. and you mean shop as i bike shop....id try to find a machine shop instead. they do that stuff all the time so itll be less
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Old 06-25-07, 06:23 PM   #3
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Extending the threading can be done if the shop has the correct dies, in good condition and knows how to use them. Also, the steerer must NOT be chromed although this is a very unlikely problem.

7 cm is quite a way but it can be done.
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Old 06-25-07, 06:27 PM   #4
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Deadsailor, you mean just cutting it down and using it as a threadless setup? The only problem with that is I would need to buy a new headset and stem to do that. Aside from that, it would work right?

The shop I have in mind has done it for me before with no problems, but those threads only needed to be extended 1 cm, not 7. The steerer is not chromed, but considering the length, I don't want to find out that it takes the poor guy an hour to do it.
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Old 06-25-07, 06:31 PM   #5
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I'm just going to emphasize the "if they know how to use it properly" part with the LBS. Make sure they have a proven track record.

I'm going to go with the cut it down and threadless it part. A new headset is like $10-$20. Stem, same price or less. Or you can gamble with the thread extension. I know of a handful of bike shops that can do this competently and I live in a large city with billions of bike shops.
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Old 06-25-07, 06:34 PM   #6
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B & H on Mission St in So Pas extended the threading on my Cinelli fork for $10 about 4 years ago. Steerer tube was also chromed. They weren't reluctant in taking the job. I knew about this shop but before I went to them I must have gone to two or three different nearby shops. None wanted to touch my fork.
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Old 06-25-07, 06:46 PM   #7
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Originally Posted by roadfix
Steerer tube was also chromed. They weren't reluctant in taking the job.
My mention of the chrome was based on at least one tool maker's (Park?) explicit warning not to thread over chrome plating. I guess it worked anyway.
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Old 06-25-07, 08:13 PM   #8
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The chrome plating warning is probably because of how hard it makes the metal. More dangerous for the die than the fork I assume. Thanks for the local suggestion, roadfix, but Reseda Bicycles is right down the street and did the cutting and rethreading on my "this-will-do-for-now" fork for $10 as well. They have been around for longer than I have been riding, they love old school roadie stuff, and they don't flinch at these kinds of jobs.
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Old 06-25-07, 09:14 PM   #9
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Quote:
Originally Posted by urbanknight
The chrome plating warning is probably because of how hard it makes the metal. More dangerous for the die than the fork I assume.
Exactly. The warning came from a tool maker, not a fork maker.
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Old 06-26-07, 02:09 AM   #10
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if you are going to get the steerer cut down by 7 cm check if it is butted. Taking that much off will mean the stem will go that much further into the steerer tube and most probably hit the part where the steerer narrows. you may need a stem with a shorter quill section.
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Old 06-26-07, 07:44 AM   #11
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+1 on going threadless.
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Old 06-26-07, 09:47 AM   #12
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Thanks mentat6059, I hadn't thought of that.

Is the threaded-to-theadless operation a sure success? I mean, there won't be any issues getting the star nut in and getting the stem to clamp safely?
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Old 06-26-07, 06:53 PM   #13
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Quote:
Originally Posted by urbanknight
Is the threaded-to-theadless operation a sure success? I mean, there won't be any issues getting the star nut in and getting the stem to clamp safely?
It is important that you cut off enough of the steerer tube to eliminate almost all (all would be better) of the threads so the new stem clamps on smooth tubing. The threads are weak points and stress raisers and the stem should not be clamped over them.
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Old 06-26-07, 07:28 PM   #14
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Before you cut make sure that you have enough steerer - head tube + new headset stack height + new stem + spacers. Measure twice and then recheck your calculations
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Old 06-27-07, 08:03 AM   #15
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Chrome can be removed with a belt sander. I've removed plenty of chrome from forks in the past. It takes all of an extra 3 minutes to thread a fork 7cm versus 1 cm.

How much did they quote you?
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Old 06-27-07, 08:17 AM   #16
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Quote:
Originally Posted by urbanknight
Deadsailor, you mean just cutting it down and using it as a threadless setup? The only problem with that is I would need to buy a new headset and stem to do that. Aside from that, it would work right?

The shop I have in mind has done it for me before with no problems, but those threads only needed to be extended 1 cm, not 7. The steerer is not chromed, but considering the length, I don't want to find out that it takes the poor guy an hour to do it.
How can you use a threaded fork with a threadless setup? The fork steerer is not long enough almonst other issues. OP - How much is TOO much for the LBS to do this job? Love these posts where the part/labor whatever is too expensive with no refrence to the cost.
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Old 06-27-07, 08:30 AM   #17
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Quote:
Originally Posted by oilman_15106
How can you use a threaded fork with a threadless setup? The fork steerer is not long enough almonst other issues.
In this case the steerer might be long enough to remove all the threaded portion and still be long enough to work with a threadless stem/headset.
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Old 06-27-07, 08:36 AM   #18
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caution - some forks are butted to save weight. Cutting threads into the thinner butted portion of the steerer tube will cause serious problems down the road. Usually you can do a cm or two but that's about it.

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Old 06-27-07, 10:38 AM   #19
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Oilman, I'm lucky enough that the fork is off a 61cm bike frame while mine is a 55cm, so I have over 2 1/1 inches of extra steerer tube. The threading on this one is about 1 inch, so that SHOULD leave me enough room. As for the cost, that's not really the issue since if I can't find a fork with these odd dimensions I'll need a new frame instead. Sorry if I was confusing, but I meant "too much work" as in not wanting to wear out my welcome with the shop. They know me and charge fair rates, and also feel bad about the run of bad luck I've had, but I don't want to walk in with a job that makes them grumble after I walk out the door.

Carpediemracing, aside from feeling around the inside, how might I know if it's butted? It's a stock fork off a mid grade Bianchi Campione, so it's probably a fork that has straight tubes so they could just take it off the shelf and cut it for the bike on the aseembly line. If it is butted, will the threadless option work or will the stemsquish the tube?

For anyone who's interested, this is what I bought. I am leaning towards keeping it threaded, but will decide when I see it in person and measure it carefully myself. Thanks for all the help.

http://cgi.ebay.com/ws/eBayISAPI.dll...140871687&rd=1

The only risk is the rake might be 5mm short, but it's worth a shot because my next move is buying a whole new frame... one with a longer top tube and standard fork so I don't have to play this game again to get it fitted correctly
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Old 06-27-07, 11:02 AM   #20
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Quote:
Originally Posted by carpediemracing
caution - some forks are butted to save weight. Cutting threads into the thinner butted portion of the steerer tube will cause serious problems down the road. Usually you can do a cm or two but that's about it.

cdr
A steerer is butted at the bottom for strength, I have never heard of a steerer being butted at the top and bottom.

vjp
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Old 06-27-07, 11:42 AM   #21
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Quote:
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A steerer is butted at the bottom for strength, I have never heard of a steerer being butted at the top and bottom.

vjp
+1

Butting at the top could cause problems with a quill stem.

FWIW extending threading is not a big deal assuming the shop has the threading tool. Beware if a "professional" balks at this type of work; he/she is a parts replacement nosepicker (remember that?), not a skilled wrench.
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Old 06-27-07, 12:07 PM   #22
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My bad, I was trying to remember why threads shouldn't be cut on a fork. It isn't butting but it does have to do with minimum wall thicknesses.

It's that the threads can be rolled onto a steerer instead of being cut into it. This means the material is sort of squished into shape versus carved out (same like forging versus machining).

The way to tell if you have rolled threads is to see if the threads increase the diameter of the steerer. If you look down the steerer, the threaded part will seem wider in diameter with rolled threads. This is because the rolling processes squishes some of the metal up (the metal moved from the valleys have to go somewhere).

If the threads aren't raised above the plain tube height the threads are cut into the steerer.

The problem with rolled threads is usually the steerer wall thickness is minimal - it's designed to be strong enough for rolled threads, not for cut threads. If you cut threads, there is minimal material left at the bottom of the thread "valleys". It's almost like you're perforating the fork. In extreme cases you can see gaps in the metal where there is no material left at the bottom of the threaded valley.

Sorry for misinformation. Hopefully this clarifies it.

cdr
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Old 06-27-07, 12:57 PM   #23
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Thanks for the clarifications. What I gather here tells me it should be no problem to have them cut threads into this particular fork. My old Bianchi one was cut, not rolled, and I'll check this new one when it arrives to be sure.

I'll be happy to get my top tube level again, but man what a PIA it has been!
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