time to get this twinscrew vice in place. Most designs i've seen have tabs cantilevered off of the bottom of the benchtop which accept the large threaded nuts for the screws. Your vice chop then is wide enough to attach at these lower points but still be flush with the top surface of the bench. In my case, with a 5,1/2" thick top, I was facing quite a wide chop. I didn't like the potential wracking that would happen to the vice if I was clamping small material...
...plus I wanted to use this last piece of wood from the original beam, which would only be the thickness of the bench itself. So I decided to plunge the vice screws deep into the underside of the bench such that they protruded from the middle.
layout looks as follows:
I then went crazy with a 1,1/4" auger bit to bore out as much material as possible
Making these deep trenches to relive the vice screw had me a little concerned about compromising the bench's strength. Originally I planned to cut the sides of a deep groove all the way across the width of the underside with my skill saw, which would have been much easier to beaver out the waste than boring with a 6" brace. But I figured it would be stronger if I could leave some of the full thickness of the bench intact, and only relieve that part that had to accommodate the screw. it actually didn't take that long to rough out:
I then made two wooden holders for the nuts that sink into the recess like so:
After fiddling a bit to get the nuts properly oriented in their recesses, here's how it looks all bolted up from underneath
I then flipped everything over and roughed out some handles
and here's the first test drive, it holds really well, don't have to apply much torque to the screws to hold this 2x4.
I kind of like working at this height, really low to the floor makes sawing with my japanese saws very easy. Might have to spend some more time rethinking my height of 34"