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Old 09-27-12, 10:09 PM   #1
evilcryalotmore
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Threading one inch fork

So i have a one inch fork, the problem is the steerer tube is 300mm long and i need to cut down and get it threaded, I have machineist that can thread it for me, and some lbs that can probably help, my question is- What is the thread pitch exactly,
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Old 09-27-12, 10:35 PM   #2
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ISO is a 1"x24tpi thread with standard 60° profile.
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Old 09-27-12, 10:51 PM   #3
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Originally Posted by evilcryalotmore View Post
So i have a one inch fork, the problem is the steerer tube is 300mm long and i need to cut down and get it threaded, I have machineist that can thread it for me, and some lbs that can probably help, my question is- What is the thread pitch exactly,
If you are starting with an unthreaded fork, verify that your stem will fit down in it. It may not have been reamed to accept a standard quill stem. If you are starting with a threaded fork, any good bike shop should have the correct die and piloted handle to extend the threads.

If I were still there, I bet I could find several bike shops within a couple miles that could do this. My old shop (B&H Cycle in South Pasadena) had this tool. I don't know if anyone there would know what to do now, though.
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Old 09-27-12, 11:06 PM   #4
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I don't know if anyone there would know what to do now, though.
The point about checking that it has a 7/8" ID (1/16" wall) is valid. Some forks not intended to be threaded have thinner walls and cannot safely be threaded and, anyway, the ID is oversize for a quill stem.

Unfortunately threadless systems have been out long enough that a decent percentage of mechanics today don't know how to properly thread a fork, even if the tool is still there under layers of dust.
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Old 09-28-12, 09:45 AM   #5
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Unfortunately threadless systems have been out long enough that a decent percentage of mechanics today don't know how to properly thread a fork, even if the tool is still there under layers of dust.
That's a good point. I wouldn't think you'd want to pay for a mechanic's first fork thread job. Everything might go OK, but this is the kind of thing that, once messed up, can't be easily fixed. I own the die but I wouldn't volunteer to do more than add a few additional threads. And I wouldn't even talk about starting threads from scratch.
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Old 09-28-12, 10:24 AM   #6
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The point about not threading a "threadless" steerer should be emphasized. The wall thickness was not designed to accept threading and remain sufficiently strong. If the steerer already has threads but they are not sufficiently long, they can be extended. If the steerer is not threaded at all, use it as is and replace the headset and stem with threadless models.
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Old 09-28-12, 10:31 AM   #7
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...The wall thickness was not designed to accept threading and remain sufficiently strong... .
This is one of those cases where a measurement is worth a thousand opinions. Many (most) threadless forks have the same 1/16" wall steerer as threaded forks, and can be threaded. Rather than guess, it's easy enough to check. You can measure for a 7/8" ID, or simply stick the stem in and check for a firm fit. If the stem has a sloppy fit, the wall is too thin and the fork cannot be used for a threaded/quill set up.

Changing to threadless is a viable option, but means added expense for headset and stem.
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Old 09-28-12, 11:11 AM   #8
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If they can Roll in the thread, there will be metal displaced rather than cut out..

it's how spokes are threaded , the valley pushed down moves metal up to form the peak.

Just make sure that if you use a quill stem it's long enough
to have the wedge down far enough to be below the threaded portion..
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Old 09-28-12, 11:14 AM   #9
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If they can Roll in the thread, there will be metal displaces rather than cut out..

Just make sure that if you use a quill stem it's long enough
to have the wedge down far enough to be below the threaded portion..
These threads are not rolled.
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Old 09-28-12, 11:18 AM   #10
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Originally Posted by fietsbob View Post
If they can Roll in the thread, there will be metal displaced rather than cut out..

it's how spokes are threaded , the valley pushed down moves metal up to form the peak.

Just make sure that if you use a quill stem it's long enough
to have the wedge down far enough to be below the threaded portion..
You fail to grasp the essential s of thread rolling.

As you point out rolling raises threads, which is useless here since the OD is already 1". If it were possible to roll a thread here (not impossible, but very difficult on a thin walled tube) the OP would end up with a thread greater than 1" in OD. The problem isn't the OD or even if threads could be cut, it's (maybe) wall thickness and ID so how the threads are produced doesn't matter.
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Old 09-28-12, 11:32 AM   #11
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But a good Machinist can roll threads , they have to be tooled up for it.

My father was a retired machinist when he passed .. made Armaments for the US Navy.

True , the usual fork threading die is a cutting tool.


to the OP : dont bother with the threading, just do the threadless conversion. thereby leaving steel tube wall thickness unchanged.

[otoh]
I used a long threaded steerer tube on my Touring bIke.
a mid ride frame repair had me knock out the headset,
got the welding done , then, I

found the long thread offered a built in headset press when
time came to put it back together ..

with just the short 32/15mm wrench I had for removing the pedals.

Last edited by fietsbob; 09-28-12 at 11:41 AM.
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Old 09-28-12, 11:40 AM   #12
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But a good Machinist can roll threads , they have to be tooled up for it.

My father was a retired machinist when he passed .. made Armaments for the US Navy.

True , the usual fork threading die is a cutting tool.


to the OP : just do the threadless conversion. thereby leaving steel tube wall thickness unchanged.
Quoting Alexander Pope said it perfectly, "a little knowledge can be a dangerous thing".

Knowing a bit about rolling threads, doesn't mean you know when it can be done (not on thin-walled tubes because they deflect) or when it's desirable or practical. In this case it simply isn't for more reasons than I care to repeat (see prior post).
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