Vices: Part 1 – double screw leg vice

The modular nature of the Moravian workbench was one of the many reasons I built this bench. If I don’t like the tool tray I can replace it with a flat board flush with the bench top. Don’t like the position of the vice screw? It’s not through the leg so I can change the back piece without messing up the rest of the bench. I’ve built two sets of legs so that I can have a taller carving bench and a shorter joinery bench.

AC528B6F-B022-4241-8C88-478F88AD01F2It’s given me the opportunity to play with a couple of ideas. Two years ago I saw one of Douglas Coates’ Ad-Vices at Oliver Sparks’ ’shop. Earlier this summer I got to examine it in a bit more detail and take some photographs. It has a clever double screw mechanism. Instead of a parallel guide at the bottom with holes and a pin it uses a threaded rod with a nut between the vice chop and the back piece. This keeps the chop parallel to the front plane of the bench.

Building one into my new bench been a rather lengthy diversion from all of the other projects I’ve got planned and I’m not sure it’s a huge improvement over the traditional guide but it’s an interesting feature. The Ad-Vice has a greater distance between the small, lower screw and the large, upper screw than between the workpiece to be clamped and the upper screw. This gives it a lot of mechanical advantage and means that the smaller threads of the lower screw aren’t under so much pressure. I couldn’t achieve this ratio and it will be interesting to see how long the lower screw lasts. If it breaks I’ll just replace a couple of components – the joys of a modular workbench.

I’ve also built an end vice, but more on that next time.

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4 thoughts on “Vices: Part 1 – double screw leg vice

  1. Cool idea. Is it possible to pin the lower screw into the chop in a somewhat sloppy mortice with the pin oriented horizontally vs. glueing it in? That added up and down flexibility may help with making sure the forces in that lower and thinner screw are focused in compression vs. sheer and may give you longer life.

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    • Interesting idea. One could put a groove around the bar and a garter inset into the chop and give it some wiggle room.
      I think when it goes it will break the threads where the nut meets the back piece of the vice. The pressure is, by necessity, uneven there.
      I’ll let you know how it goes.

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      • Not sure I understand your reference to “where the nut meets the back piece of the vice,” and the pressure there. From the looks of your video, it looks like your rounded over nut will allow it to rotate fairly well in the vise support block (let’s call it that as I am not sure the official name) that rests between the top and lower stretcher. The video seems to show that flexing fairly well.

        My concern I think would be addressed by the groove and garter idea you mentioned I think. I think a through pin would work as well as I think it just needed to flex up and down to allow the toe in lean on the chop. I think that and your rounded nut would seem to let it survive quite a long time. That said, I think your groove and garter idea may give it even more flexibility and perhaps last even longer.

        Looking forward to your end vise post. I have not done that but want to and cannot settle on a plan. Hopefully what you post will help me out … either that or give me one more thing to contemplate.

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