A Rigger's vise is neither common nor cheap. I wanted to try my hand at splicing some wire rope(Liverpool splice) but an entry level vise is around $300. Nice ones are more than double that, way out of budget.
The goal for this project was to use readily available parts and tools while saving wads of cash. Corrosion resistance is always a welcome bonus. The aluminium plate and stainless parts are all on ebay, cheap. A hand drill could be used in place of the drill press, there is very little precision required on this job so long as the tapped holes arent too loose when finished. One could even cut the aluminium with a hack saw(it'll only take a couple of days) or sawzall(forget pretty). The spring, sliding jaw retaining screw, countersunk heads and pretty work are all optional.
Use whatever size pivot and jackscrew hardware you feel appropriate or whatever size thread taps you have. I think a fine threaded 7/16" would be the ideal for all three jackscrews but the 5/16" and 3/8" seem to apply ample clamping pressure. The diameters of the jackscrews and pivots can always be increased to beef it up.
You can also fashion the jaw 'teeth' to accomodate the wire diameters you expect to be working with. 1/8" fits well in my smallest groove, not sure how big she can go yet. A set of 'dentures' could even be made which slip over or bolt to the ends of the jaws to change the size/profile of the clamping surface.
As you may have already guessed, I'm marlingspike deep in Brion Toss's The Complete Rigger's Apprentice. What's next, casting bronze eye thimbles?
