Hi Charlie,
I installed my Veritas twin screw vise a little over a year ago, so I'm a bit rusty on the procedure. Seems to me I followed the Veritas installation instructions, and things went fine. Just took some measurements, and here are the results, pretty much in order of your questions:
- The centers of the screws are 4" below the top of my bench ( actually measured 1 3/4 from the bottom of a 2 1/4 thick top). The big thing here is to mount them low enough to allow the top of the square flange around the guide screw to clear the bottom side of your top. Mine sits about 1/16th below bottom side of the bench top.
- I mounted mine so the screw guides are inside the end board of the bench. As I remember, the hole isn't sized for a press fit, since the screws on the flange actually hold the guides in place, and a little slop allows for some minor adjustment to align the screws, should your holes be slightly off. The skirt on that end of my bench is 2 1/2" thick, and 6 1/2" deep to match the face of the vice and I haven't seen any sign of weakness.
- I did taper the jaw, per Veritas instructions, and it's worked out okay, There is quite a bit of "droop" in the moveable jaw as you open the vice more than 6-8 inches, and the taper does help to square it up. Wasn't too big a deal to do the taper, I just shimmed one side, then ran it through the Planer. Don't remember the size of the shim, but it wasn't hard to calculate. On the other hand, my Record face vise doesn't have a taper, and it works just fine. It does have a lot less sag, however, so that might account for the difference.
- I did put the radius on the outer jaw, primarily for the sake of my hips. My shop is pretty crowded, and sharp corners tend to "reach out and touch" me when I'm scurrying around working on a project. Don't know any other reason for doing this, however.
- The chain drive is somewhat sensitive to slack in the linkage. Veritas provides a 1/2 link. as I remember, so my guess is much more slop than that and you'll start getting slippage, which puts the jaws out of parallel. Eye-balling a tape measure between the centers of the screws, it looks like mine are spaced right at 17"
Last thing I can think of is to be sure and put the "rub bars" above the screws on the underside of the bench. These help lessen the sag as the jaw extends, and without them the screws will bind enough to cause the chain to jump on one screw.
Good luck with the install. I really love the vise. It sure came in handy on my last project ( a new entry door)
Ron Kolakowski