Perfect the First Time?

[WESTERNAERO]

The Colt 1911 has a flaw. The trigger lock safety could be better placed.

this is probably the best example I know of.
Thread root diameter and angle of the thread cut(not the pitch) hasn't changed in 150 plus years. All threads, whether metric, Whitworth, or SAE, course and fine, all follow the same basic engineering that was layout almost 2 centuries ago, and it hasn't been improved upon. Methods to from threads have improved, but the geometry has remained the same.
Even the thread pitch(threads per inch) is very similar throughout the world. They may call it threads per millimeter, but the count is extremely close. You can duplicate most metric threads on a American made lath using preset thread settings.
Westernearo may be able clarify that. But this has remain unchanged pretty much since the day one.


A nut from the civil war will thread on a bolt made today.

Nice job Bob. The only thing I would change about what you said is metric threads aren't designated by threads per millimeter per say. Metric thread pitch is a crest to crest measurement. So a 13mm x 2.0 means the threads are spaced 2.0mm apart. Multiply 2.0 by .03937 is .0787", so your feed rate on a lathe would be .0787.