# Is there a way to fix stripped crank arm threads on old Rollfast?



## Rayban (Apr 17, 2011)

Anyone know a way to fix stripped crank arm threads on old Rollfast?
Thanks


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## bud poe (Apr 17, 2011)

You can maybe try a "heli-coil".  It's sold as a set that basically lets you tap the hole for a larger threaded insert, the end result being a repaired threaded hole of the same size that you started with.  You'll need to determine the proper thread pitch of the pedal and buy the correct "heli-coil" for it.  Takes a little patience, but should work....
Or just buy a new crank-arm...ebay or someone here??
Good luck!


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## Rayban (Apr 18, 2011)

Thanks for the info, will check out helicoil.  also looking for new crank..it's a one piece with both sides all together.


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## kunzog (Apr 20, 2011)

An old bike shop mechanic would braze the old crank threaded hole closed, drill and retap. Your best bet is to buy a new or used crank.


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## HIGGINSFOREVER (Apr 20, 2011)

Any good bike shop should have the tap to rethread that.I have a set of 1/2 " and 9/16" left side and right side threads.Park tools sell then.                                                                      '


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## bud poe (Apr 21, 2011)

If the hole is completely stripped out, re-threading only works if you want to go to the next size up, correct?  With Helicoil, you can restore to the original size...
In my Island Cycle catalog (1930's reproduction) they offered crank end replacements that a bike shop would weld/braze on for you..too cool...
Good luck!


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## HIGGINSFOREVER (Apr 21, 2011)

bud poe said:


> If the hole is completely stripped out, re-threading only works if you want to go to the next size up, correct?  With Helicoil, you can restore to the original size...
> In my Island Cycle catalog (1930's reproduction) they offered crank end replacements that a bike shop would weld/braze on for you..too cool...
> Good luck!



I have never seem one that could not be taped.If your using 1/2" pedals you use a 1/2" tap


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## bud poe (Apr 21, 2011)

Not trying to be difficult, but if the threads on a 1/2" hole are completely stripped out, sure you can run a 1/2" tap through it but it's not going to somehow restore the metal that is no longer there.  If the threads are only slightly damaged, yes, running a tap through will probably be enough to let you get a pedal back on, but if they're totally stripped out the same size tap does nothing...Please correct me if I'm misunderstanding something here...


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## old hotrod (Apr 22, 2011)

Bud Poe, you have it correct, if the pedal has been loose for a long time, it pulls threads out of the crank which removes material from the inside of the hole. Running a tap through only removes more material as the tap cuts the deformed threads. Crank may be "usable" and the pedal may go in but any threads cut are damaged and may be prone to fail...assembly is not as strong as it should be so it is a risk. Heli Coils and other thread inserts may be a good fix and may not since the tap used opens the end of the crank to the OD of the insert making it a little weaker...


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## HIGGINSFOREVER (Apr 22, 2011)

The metal is still there it is just flattened out.The only time to use a heli coil  is if you have to drill out the hole.Old hotrod have you ever had to retap a spark plug,if you had a old ford flathead that was a easy fix heli coils were unheard of back in then days.


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## Gordon (Apr 22, 2011)

You could use a set of pedal extenders, but I think they put a lot of stress on the end of the crank arm and the pedal shaft as well.


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## pgroah (Apr 22, 2011)

I would try to run a tap through it to see if you could make it workable.  As for the helicoil, I have never heard of a left hand helicoil maybe they exist. I think brasing or welding, to fill and then drill and retap.


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