Kopal Milling Clamps

[magicniner]

We used Kopal clamps on a Hmc at work to hold 350x350x25mm plates for machining and they gave great clamping force but I would recommend making some steel bushes that you can knock on the knurled part of the screw to increase the strength of the Allen socket because they are prone to breakage if you over torque the screw so the coller stopes it ripping apart and becoming useless. They will be a pain to get off if you want to service the clamp but it's doable.

I've milled the hold-down bolt hole on two of mine out to a slot to take M10 custom bolts but it's a common misconception that the hold down bolts need high torque, they don't.
Kopal clamp hold down screws should be hand tight and not swung on, they only need to be tight enough to stop the clamp easily moving out of position before any clamping force is applied, the tool provided has the right dimensions to stop the uninformed swinging on the screw and applying excessive torque ;-)
The whole point of the design is that applying the clamp uses the hold down bolt as the pivot point of a lever with the work contact and the back end of the clamp as the pressure points.
If you break the screws you're not understanding the correct usage of the clamps :D

- Nick