I recently wanted to mill the face of a piece of wood that was too wide to grip in the vice. I didnt want to clamp on the top surface because I wanted to skim the face without shuffling clamps.
The attached photo is pretty self explanitory. Its two pieces of angle iron both drilled to accept T bolts to clamp them to the bed of the milling machine. One piece of angle iron is then drilled to accept two headed bushes that are tapped M12. The headed bushed were Loctited in. A loose piece of steel then acts as the moving jaw of the "vice" and two socket head screws allow the clamping fore to be applied. The movement of the loose jaw is minimal as bigger movements are accomodated by moving the T bolts.
It worked fine for my wood milling, I dont know how it would perform on metal pieces.
The attached photo is pretty self explanitory. Its two pieces of angle iron both drilled to accept T bolts to clamp them to the bed of the milling machine. One piece of angle iron is then drilled to accept two headed bushes that are tapped M12. The headed bushed were Loctited in. A loose piece of steel then acts as the moving jaw of the "vice" and two socket head screws allow the clamping fore to be applied. The movement of the loose jaw is minimal as bigger movements are accomodated by moving the T bolts.
It worked fine for my wood milling, I dont know how it would perform on metal pieces.