Gunner Asch wrote:

On Mon, 16 Aug 2010 13:02:39 -0700, Tim Wescott
wrote:

On 08/16/2010 12:07 PM, Karl Townsend wrote:

Vice-Grips are not intended as machining clamps. Try the clamp bars in
the holdown kit, they are intended for the use and will give you high
clamping pressures when used properly.

BTW, have you been reading the Machining Fundamentals book? It explains
various work holding scenarios including the clamp bars.

I have been reading it, but not about clamps.

The majority of parts you make will have workholding issues. This is
probably the number one thing that separates a good CAM programmer
from a terrible one. You have to know how to make a part before you
automate it.

I'm big on optional stop in my program for clamp moves. Often a clamp
can be moved while the machine runs. If you got it moved before it
gets there, flip optional stop off and machine keeps going. if you
didn't finish, machine stops and waits for you.

Does anyone make NC clamps to automate that operation?

I really wish I were being flippant here, but I have this horrible
suspicion that it's been done, and commercialized.

Air clamps operated by the control and an M code, along with magnetic
chucks and form chucks are all commonly used in manufacturing.

Hydraulic clamps are very common, both on heavier work where more
clamping force is required, as well as on compact work where there isn't
enough room for an air cylinder with sufficient force. Air over
hydraulic intensifiers are often used to allow a pneumatic supply to
operate a hydraulic clamp.

The commercial CNC controls pretty much all have some general purpose
output signals available controlled by M functions to control clamping,
signal indexers, palette changers, robots, etc. Really very easy stuff
to do, and just as easy to do on home machines if you have a run of
parts big enough to justify the fixturing.

If you search on McMaster for "clamping cylinder" you should find
pneumatic and hydraulic cylinders intended for work clamping use. Even
some tiny hydraulic clamp cylinders that have threaded bodies to install
like a bolt.