When I first built my French Roubo-style workbench, I put a sliding deadman on it to help support doors and long panels. But I have long intended to replace that deadman with a sliding leg vise.
Roubo actually shows this arrangement in one of his volumes, and it is a tempting morsel. However, as you will soon see, it is also an engineering challenge.
I’m tempted to build it because it would be the final solution for dovetailing and working on the long edges of boards. One end of the work would be held in the regular leg vise (located on the left leg). And the other end would be grasped by the sliding leg vise. With a long bench (mine is 8′ long) you could hold almost any piece of wood you would find in a furniture-making shop.
The engineering challenge comes when you try to build it so it is sturdy and won’t damage the bench. It can be done, of course, but adding the sliding leg vise as an accessory requires some careful thought.
Luckily, industrious reader Bill Liebold has built the sliding leg vise on his 12′-long Dominy-style workbench with an end vise. He is smitten with the functionality of the sliding leg vise, but is still working out the engineering aspects of it.
The real issue is that the sliding panel moves in a groove that is routed into the underside of the benchtop. When you really cinch down the sliding vise, it can bow out the front edge of the workbench.
“I was able to bow the front edge of the bench top but that was with far more pressure than I need to hold a piece of wood,” Liebold writes. “I did it to see what would happen if I overtightened the vice. I like to experiment.”
If you are considering adding a sliding leg vise, you are going to want to change the groove in the underside. Personally, I’d locate it as far back as possible from the front edge of the benchtop. Liebold thinks it would be best to have the groove start 3″ in from the front edge, and to use a 1″-thick tenon on the sliding panel. I think that sounds about right.
There are lots of other ways to go about this, I’m sure. And now I’m toying again with the idea of adding a sliding leg vise if I can just get the engineering worked out in my head.