I vote for a screwless vice.
I built one recently - also for the excercise. I actually designed it when I first got my milling machine without a vice. I found the materials in scrap (very nice cast iron for the vice itself and 1/2" cold rolled steel for the baseplate) and machined the outlines of all parts back then, only to be offered a very heaviy and nice vice on rotating base for $15.... as you can imagine, the project got put in the shelf.
I finally finished it about a month ago. Works a treat. Its 4" wide and opens to almost exactly 6". The grooves for the cross-pin were milled with a 1/2" ball-end cutter.
I built one recently - also for the excercise. I actually designed it when I first got my milling machine without a vice. I found the materials in scrap (very nice cast iron for the vice itself and 1/2" cold rolled steel for the baseplate) and machined the outlines of all parts back then, only to be offered a very heaviy and nice vice on rotating base for $15.... as you can imagine, the project got put in the shelf.
I finally finished it about a month ago. Works a treat. Its 4" wide and opens to almost exactly 6". The grooves for the cross-pin were milled with a 1/2" ball-end cutter.