The Stein bike tool company makes a piloted tap which I think is 25mm x 1,
and sells it with a helicoil repair kit and oversize "steal-a-crank"
extractor bolt set for a permanent repair of cranks with damaged threads.
The best part of this system is probably that the tap has a pilot to guide
it. Bicycle Research used to make a piloted thread chaser for cranks, but
it was for the smaller Italian/Japanese thread diameter.
David Feldman
Vancouver, WA
> Jan:
>
> Assuming that you have an extra (i.e. sacrificial) TA crank
> puller, you might try converting it to a tap/thread chaser.
> I imagine that would involve reducing the height of the
> threads at the front and filing a groove longitudinally to
> obtain a cutting/thread-forming face. Reducing the height of
> the threads at the front so that it is tapered might allow
> it to get in a bit deeper on the remaining threads in the
> arm without crossthreading. Are you working with a steel or
> alloy crank?
>
> Charlie Young
> Honeybrook, PA
> > Does anybody know where I can find a tap to chase the
> > crank extracting threads on a TA crank - 23 mm
> > diameter... It's not a TA crank, and it's worth saving,
> > but somebody banged a hammer on the outside to fit the
> > crank, and it distorted the threads so the extractor
> > doesn't fit any longer.
> > I have tried to file out the damaged part, but can't get
> > the extractor to go in without cross-threading. If I had
> > the tap, I could chase/retap the threads, and it should
> > work.
> > Does anybody have one who'd be willing to lend it? Or does
> > anybody know whether this is a standard size that my
> > hardware store could order?
> >
> > Or does anybody have other ideas of what might work?
> >
> > Thanks,
> >
> > Jan
> > _______________________________________________
> >
>
> Charlie Young
> Honeybrook, PA