5 ms·
The remaining problem is that metric threads are specified by the mm between peaks, whereas US customary threads are specified by threads/inch. It's not immedi
by mauvehaus 2y ago
The remaining problem is that metric threads are specified by the mm between peaks, whereas US customary threads are specified by threads/inch.
It's not immediately obvious to me (not a machinist) that the 127/50 ratio gets you the ability to cut metric threads without a mess of other head-scratching because you're now dealing with period instead of frequency.
- analog31 2y agoIndeed, the charts for cutting metric threads are complex, and I'm not sure all of the standard pitches are even possible. The lathe that I use hasn't had its threading gears installed in ages. A weird historical tidbit is that after WWII a couple of standards emerged for bicycle parts in Europe, where they used metric diameters and inch thread pitches.
- mauvehaus 2y agoThe Italian bottom bracket threading standard is completely insane. Like, how do you even cut that, and why would anyone come up with that in preference to literally anything else?
- analog31 2y agoThe only thing I can imagine was a supply of American machine tools from the rebuilding of Europe after a WWII. You can always cut any diameter, only the thread pitches are ruled by the capabilities of the lathe. Also, left handed threads involve their own issues since the spindle chuck wants to unscrew itself.