11.5 tpi - how to do it?

[steamer]

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Great!


But only if I can call 1.6667mm pitch buttress threads 1 totally wicket bizare thread unit ( 1 TWBT)

 

[shred]

I suspect some thread pitches are driven by marketing: "The competition's new lathe can cut 96 thread pitches. We need more! Joe, throw another gear on there! But Boss, nobody will ever use those. I don't care, I want more! We'll advertise 128 threads! The North Bend Lathe Company Name will live forever!"

The rest could happen like so: "Well, old Eli never was much for sitting down figuring things out or making drawings, he just sorta cut a thread that looked about right. When the Army wanted a million of his frambulators, they took Eli's prototype to a guy to make drawings and he didn't dare change a thing. Eli always did get a chuckle out of that five-and-three-quarters tpi"

 

[steamer]

The 128 I did was for a needle valve on a model airplane engine......which came first the lathe with 128 or the part with 128.....well some mysteries are better left untold....

Dave