"Bob Powell" wrote in message
om...

Few folks in this group under 40 may know what an automatic screw
machine is, how they work or that they go back at least 120 years.
Not that I know more than from reading a book. Bunch of change gears
to set feed rates and cycle timing, and hand-cut cams to cycle through
changes of tools, feeds and stock advance. Net result is loading a
20' bar, then coming back in 20 minutes to empty the bin of whatever
part it just made 300 of. Need a turned length of .750"? Set up
change gears for a cycle that feeds at .010" per rev and cut a cam
that dwells on that cycle for 75 spindle revolutions. Something like
that. Pretty darn close to numerical control. Efficient enough
overall they are still in use all over the world today. The older
Machinery's editions have sections on programming them.

Haha! Ask Dave ("Why"). He still runs them. Belt-driven ones, at that. g

--
Ed Huntress
(remove "3" from email address for email reply)