Special taps

[Mutt]

I take it you don't fool with 20's/30's/40's/50's vintage Harley motorcycles, huh? A normal (modern) throttle cable may end like that, but vintage Harley cables do not. Try sticking one of the modern cables inside a 1948 Panhead handlebar and see how it looks nothing like an original cable. I have been selling these cables I build for 15 years now, just tired of buying the spools from someone else, when I can machine them when I need them for about 10¢ worth of material. I talked to atap manufacturer. He told me they can't make a standard fluted tap like this because the flutes would leave no center. I later learned about forming taps, of which this would have to be.

 

[4ssss]

Scuzzzzzzze me

 

[whitmore]

I talked to atap manufacturer. He told me they can't make a standard fluted tap like this because the flutes would leave no center. I later learned about forming taps, of which this would have to be.

Well, maybe it's not that bad. The coarse pitch is a problem for something that narrow, and the self-feeding nature of standard
taps won't work well, BUT you can make a piloted-boring tool that would work, and hand-feed it with a section of 3/8-14
threaded rod brazed to the shank. Then the progressive deepening of the thread just requires
you to have three or four different-depth tools that can be indexed so the teeth follow the same helical path.

There's some tricks with EDM, too, that can make an internal thread without torque and chip clearance issues. That, you'd
have to job out, though.

Last, there's casting; a zinc/aluminum alloy can be cast around a mandrel, then you just mount mandrel in lathe,
turn the exterior surfaces, and unscrew from the mandrel...