A knife vise I recently completed.  Chrome moly tubing, and a .375 thick tab.  We drilled and welded a top bottom/top piece inside the tupe (around the screw head) so the clamp would move up and down with the screw action.  I used a SS bar, square on one end, tapered on the other for as a backer plate for the knives.  Pool balls for handles which have been epoxied to the screws. Works great.

I will be adding a piece of leather to the encased clamp, and a piece of leather to the SS bar as well to aid in holding and preventing damage to the knives.  

Nice tool and nice work on it!

Steve
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Potomac Forge
W.F. Moran Jr. Museum & Foundation