And along the same lines, cam operated spring forming machines. Often
very complex programming via specially machined cams. Of course this
has been replaced by CNC spring formers which are more suited to quickly
changing jobs rather than set-ups for long runs.

However, is there really that much difference between holes punched in a
card telling a machine where to go and profiled cams telling a machine
where to go? I guess one may have a mechanical linkage where the other
may have an electrical linkage. Either way, they are both effectively
numerical control.

So where does the line cross to being true NC? Is there a definition of
this point? I remember that my Comp Sci teacher once defined a computer
as being such because it could modify it's own program if needed, rather
than a set of codes that were simply repeated from memory. I wonder if
there is such a (historical) line or point where mechanical becomes
defined as NC becomes CNC?

Koz

Bob Powell wrote:

snip


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.

snip
Bob