I put in a bench vise today and, as per advice from this group, used bolts, nuts and washers. I drilled a couple of flat-bottomed holes in the bench top, just deep enough to keep the bolt heads below the level of the bench surface.
Once I'm pretty sure I've got the vise the way I want it, I'd like to fill in the holes with...something. Something that would leave the surface flat afterward, maybe after sanding . Ideas? Wood putty? Epoxy? (I'm probably not brave enough for that one) Something else?