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80 threads per inch fastener close-up.
Fullsize image: https://diqn32j8nouaz.cloudfront.net...r_fullsize.jpg
https://diqn32j8nouaz.cloudfront.net...h_fastener.jpg
Previously:
https://www.homemadetools.net/forum/...2502#post96471
https://www.homemadetools.net/forum/...3730#post99885
https://www.homemadetools.net/forum/...7894#post86435
Now thats some fine threading
That's not any thread profile I've ever seen - it doesn't really even look like a thread.
1/4"-80 is not uncommon as micro adjusters in lab gear for optics and/ or high vacuum conditions.
Tutorial for the curious: Fine Adjustment Screws
My lathe will cut 112 per inch never had a need to but I am going to point up a bit and give it a try.
-Good luck!
AFAIK, a single-point 112 TPI threading tool would need a 1,29 thou (32,7 microns) tip radius and a 5,48 thou (0,139 mm) DOC,
but merely choosing the right tool alloy to make that tip strong enough for 303 SS is beyond my knowledge horizon.
Then, DIY-ing a tool grinder for that geometry and checking its precision would be quite an undertaking...
Then making a durable tap is a whole different job.:)
I hear ya it would have to be a fine point to cut the 0.009 pitch.