4 in. Drill Press Vise

No

While it shows as a 4" vice I had to file off a bit of casting flash in the handle end of the slide slot. Took about 30 seconds and then it opened up to right about 4"+. Just open it up as wide as you can and It should bottom out at the handle end by the number 4, If not just clean out any slag/flash in the slide slot at that end.

5 1/8"

I think those grooves might refer to what is called a stove bolt.

I looked at several bolt configurations and sizes from 1/4 inch and larger but the next job would need a different setup. I stopped bolts and used clamps to move it for use but even then look to the underside of your base to find an even surface to clamp onto. Many do not have a decent way to make the bolts or clamps useable with wing type nuts but clamps were usually best for easy changes.

Probably the easiest way is mount it on a thick piece of OSB or 2 x 12 using carriage bolts that are countersunk on the under side so the board will be flat on the bottom. Use washers and nuts on the top. Then when you need it you could just clamp it to the drill press table. You could also install carriage bolts through the mounting board in the other direction with the bolts lining up with the slots in the drill press table. Then use washers and wing nuts on the under side to anchor to the drill press table. Hope this helps.

My scale goes only up to 3.3 kg or a little over 7 lbs, and it is some heavier than that. To make a guess, I would say that it is probably over 10 lbs too.

My vise fits well on my Ryobi 10 inch press. You might make a paper template of the table on your 8 inch press and take it to the store with you when shopping for your vise to see that the mounting holes match up. If not, explore the possibility of a smaller vise or making a mounting interface pad with a small piece of quarter inch plywood.