Originally Posted by
nitewatchman
Those are Lithograph Offset Press Plate Clamps. These were used on large offset presses to clamp the lithograph plates to the press bed. They are wonderful! I have a handfull, 20 or 25, and a wrench.
To use the clamps you determine where the edge of the part is, add 1/16" and drill a 1/2" hole 5/8" deep into the fixture. The clamps have a hinged toe that bears against the wall of the hole and kicker that bears against the other side of the hole. There is a screw in the center that bears against the kicker and forces the clamp over while rotating the top of the clamp down towards the top of the fixture. The clamping force to the side and down is very high. With one clamp in place you cannot tap the part side to side in the fixture without really whacking on it.
The fixture is made of a piece of scrap G10 and has a 1/4" high stop on the back side that the part is clamped against. There is a 3/4" tooling hole in the center to roll in X-Y Zero and Z zero is on the top of the fixture pocket. The part is 1-1/2" x 3/4" x 3" +/- .005". In this fixture the part is machined on both ends, the top cut to height, center slot is cut and ID is engraved.
I got these while working in a printing plant as a summer engineering intern in 1971. The Litho Press were being scrapped and there were thousands of these clamps that were thrown away. I wish that I had taken all of them!
nitewatchman