Stripped fork thread
 

Hi,.

I have a 1 inch fork that is slightly stripped, I was able to remove the fork,( headset) but have no luck reassembling, any way to DYI the thread? thanks:cry:

With the proper equipment, sure.

The fix I've done is to melt brass into the damaged threads, then cut new threads into the brass. But that assumes access to brazing equipment and a steer tube die. Unless it's a particularly valuable or unusual fork, it's probably more cost effective to replace the whole fork.

Most bike shops will have a threading die that can be used to "chase" (clean up) the damaged threads and that may fix your problem. The die will work if there is enough metal to reshape. If the threads have been damaged to the point the thread metal is gone the die can't fix it. If the fork and bike are particularly valuable or of sentimental value, a frame builder or someone who knows his way around a brazing torch can flow brazing brass over the damage area and cut new threads.

for More Metal.. the scheme Is, Lay in a layer of molten brass , then re cut the treads in the Brass. ..

Of course I cannot SEE the extent of your issue ..

If you're replacing the fork, you might want to consider threadless. There are a few 1" models around, and it allows you to run 31.8 bars, which is a worthwhile upgrade IMO - a fair bit stiffer, and the bar clamp is a sensible size for drop bars, unlike the traditional diameter which was always a bit iffy with all the torque on it from weight on the hoods...

1" threadless stems are unobtainable, but you just use a shim. Looks pretty neat:

http://bikeforums.net/attachment.php...hmentid=359529

Although if you want a 17° stem like that, there's the Thomson Elite, and not much else.

Depending on the type and degree of the thread damage a chasing of the threads and reassembly with LockTite might work well enough. Andy.

Buying the die to chase/clean up the threads-is EXPENSIVE-$50-$100
Not worth it
If you are a cheapskate-get a thin triangular file-harbor freight
and attempt to clean up the threads with it
Start somewhere-where the threads are "good" and work up towards to top
Yes you will be cutting out some metal-but so will a die
So take your time-it can work.
$5 file-triangular
Real cheapskates can do it with a table knife with fine sandpaper wrapped over the blade-file is better.
No point in paying a bike shop $50 to repair a $30 fork-unless it is a GREAT hard to replace fork

TAKE YOUR TIME
Pictures would help-sometimes threads are beyond redemption-but if it threaded off-you should be able to thread it back on

If the threads are really iffy-don't tighten the headset "too much"
Luck
Charlie

No one ever suggested buying the threading die and what you propose as a fix is a lot of work for what a bike shop should do for $5 if you take them the bare fork. Running the die over the damaged threads will take 5 minutes if they are slow about it. They can also inspect the damage and let you know if it's so bad that cleaning up the threads won't help.

One note.

There's a difference between "chasing" and cutting the threads.

The last thing you'd want to do when dealing with a partly stripped or damaged thread is remove more metal through filing, or by using a cutting die. Those would remove metal, but do nothing about raising the peaks so they're high enough to to engage the headset cup or locknut.

The objective is to flow metal and reform the peaks in a process more similar to rolling threads than to cutting them. This is what chasing is about. Of course this only works if there's enough metal there to salvage.

The tool of choice for this is a decent condition steel threaded upper cup. Oil it well and work it down the thread by degrees, backing off as it jams, and hopefully making progress three steps forward and two back. Keep it well oiled, and remove completely and flush to clean off any fine metal shards which may accumulate.

The chasing process isn't magic, and can't add metal, but if the old thread was distorted, it can flow metal from the sides of the thread form back to the peak, raising it back to profile.

Otherwise, you need to add material via brazing and cut fresh.

There is another option, there's enough thread to hold slightly. Replace the quill stem with a threadless adapter stem and use a threadless extension. The upper part of the adapter needs to be jammed down against the locknut to hold everything together. Even if completely stripped the headset can be adjusted by setting the stem tight enough to hold, but no full tight. Then it can be tapped down to preload the headset, and locked in place.

Or you might be able to finesse the job by using an adjustable collar under the adapter.

What's best depends on the condition and worth of the fork, and the cost of replacement vs. other parts needed for a change. But I suggest you start with the simplest, cheapest alternative, and scrounge up a steel cup, and give chasing a chance.

Very interesting technique.. with the threadless stem adapter that is. I've often wondered if that could be applied, so I must ask have you actually done this?

$5-??
a bike shop in china or south america would do it for $5
Here?? USA?? They can't make a living charging $5 for machine work.
Folks ask for How to fix it advice-and your advice "bring it to a bike shop it will be cheap"
It is NEVER cheap-even cheap stuff isn't cheap.
And DIY cleaning up threads-is a useful skill-it would take maybe 10-15 minutes-
and the triangular file-useful tool
Hauling it to bike shop-+$20

Yes and no. I did a field repair of a stripped headset using a piece of PVC pipe and the quill stem. I cut and fitted the pipe to fill the gap under the elbow, adjusted by the tap, tap method and tightened the stem to the max. The bike completed the trip (maybe 3-400 miles) without issue.

I didn't suggest this simple approach since folks here are too finicky to accept this type of jerry rigged solution, and who wants a bike with a piece of pipe under the stem. OTOH if this were my beater or commuter bike, I wouldn't hesitate to do this if chasing didn't work. Keeping a beater on the road for $1.00 makes more sense than sending lots of dough on it.

Yeah, I was thinking the same thing. We get $25.

I agree that cleaning up dinged or nicked threads is useful, and use both triangular and thread files for all sorts of work.

BUT

It's not appropriate for a stripped thread, since the issue is that the peaks are too low to engage the mating part. Filing away more material won't raise the peaks, and so is useless in this application.

Okay that makes sense, I've done something similar I had a mtb with a threadless fork and the star nut was utterly useless, had to hand preload the headset while tightening the stem bolts.

If the threads are shaved flat-that is a wrap-it is DONE-
But since OP screwed his headset off-he still has some threads-he just can't rethread it-because he has threads pushed into the grooves-
the file removes some material-but it also pushes some -a little-back into place-now badly bent threads-tend to "break off" their tips anyway-
If something actually has been screwed out-and it didn't "cut/shave" its way out-meaning with lots of metal shavings-it is frequently salvagable-but no point in hauling a $20 fork to a shop for a $25 repair
The "bring it to a shop" useless advice for a cheap part.
And anything involving an expensive tool-useless also-
Who other than a bike shop will have a special sort of die for rerolling threads-and msny of them-probably just have a thread cutting die
No way is ANY sort of machining just $5-pure BS to suggest that-can't stay in business charging that little-quality tool is over $100-

Not bad-I like that idea!

You and I agree that bringing it to a shop is going to be too expensive except for a collector fork.

Where we disagree is cutting vs forming. Often stripped threads are sort of half and half with the mating part (headset in this case) with the thread mashed rather than removed. (if it's actually shaved off it is toast). Filing doesn't flow metal it removes it, but using a steel headset cup as I described earlier might flow enough back to make it workable, whereas cutting more away definitely won't. Since it's a no cost DIY deal, there's little to lose - except the time to scrounge a good condition steel cup.

I also proposed other DIY make do solutions.

$5 repair=BS

Varies by area, season, type of shop, and the relationship. If the OP has a relationship with a "blue collar" shop, they'll probably look, advise, or maybe give it a go for a couple of beers (this time of year). Certainly a co-op would. Whn I was in retail we often helped regulars out with Hail Mary stuff like this at no charge.

Without a relationship, allthe OP is likely to get is "it's stripped, you need a new fork"

OK- yes I have done the same-used a steel headset as a "die"-but usually after I have done a bit of triangular file dressing first-especially to get it started- he says he can't get it back on-meaning can't get it started-
File-useful tool-
Now I have also used a knife to "straighten" threads-no sandpaper-just a thick bladed dull cheapo knife-carefully of course

Sure if he has a relationship with them-they will cut him a deal-but no finicky repair involving threads and a pricy tool is usually $5-it shouldn't be-expensive tool -some expertise-potential to fail in which case customer claims they "broke" his fork-"charged me for nothing" situation-sucky sort of repair since it takes time-but might fail

I just reread the post, and it's vague as to what he means. I took it as the fork is stripped and can't be tightened, but it could also be I can't get it started which is a horse of a different color.

If the thread is basically but he can't get it started, probably because dropped the fork and dinged the first thread, or cross threaded it a turn or two by starting badly, then there's something to work with, and all he needs to do is dress out the local damaged area, so the cup will install. He just has to be careful to remove only as much material as necessary so there's still enough to hold on the cup and locknut.

This is the kind of thing that any of us could look at and assess in 5 seconds flat, but it's hard to advise sight unseen. IF the OP is in above his head he should seek the opinion of someone and proceed accordingly. If here's a co-op or local fixit guy that's his best bet, a least for a consult.

I would not have interpreted it that way. Actual text was "no luck reassembling" and I would normally assume only a part of the threading was damaged. Chasing it would be my first attempt and I've done that numerous times with reasonable success.

I've also had a thread that was re-chasable within a few millimeters of where needed --and actually used ball bearings that were one size larger to raise back into useful threads. (But that was a little weird and only done because existing parts HAD to be fixed)

Given that the thread title is "Stripped fork thread" I think the best we can say is that the OP was decidedly ambiguous about the nature of the problem. :notamused:

But certainly it makes sense to start with the simple fixes, like chasing the threads. A thread file is handy for those times when you can't start a threaded piece:

http://www.miataturbo.net/attachment...air-files2-jpg

What are those tools?? Thread files?? Wow-didn't know there were such things-
Are they UNIVERSAL- one file fits all??
Or my guess you need a specific file for a specific threading??
Looks like maybe you get two "threads" per file?
Hmmmm- never knew there was such a thing??
Wait-are these "taps"-for the hole-not for the male "part"?-?? What are they??

DBG?
How did you use ball bearings to squeeze up some threads?? Somehow pushed them thru the grooves-into the metal-squeezed up some metal?? I'm mis-reading what you wrote I think?
MAYBE you mean your repair required bigger bearings once it was done?
How did you do that??-Maybe captured them in pliers-squeezed-turned the pipe with some help?? How??

I could picture pushing ball bearing thru a grove-but I don't think you mean that??