Randy Klein

After reading Chris Schwarz's new Workbenches book, I was inspired to make a protortype twin-screw vise. But after having made one and playing with it for a little while, I noticed two deficiencies. One, it is a little overkill (size-wise) for holding drawer components for dovetailing and such. Two, when clamping wide panels, the vise seems to put more pressure on the edges than the middle.

The first problem I solved by turning the twin screw into a triple screw; I added a shoulder vise screw in the middle. Now I have two different ways to dovetail drawer components.

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If I'm only doing one and the vise is already in the twin screw configuration, I can use it in the traditional fashion as shown below:

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But if I'm doing multiple drawers and/or the mood is right, I can thread in the third screw and use it like a shoulder vise.

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The second problem I solved by curving the face of the vise. Now it acts like a curved caul, distributing equal amounts of pressure across a larger portion of a panel. The curve has an added benefit in that it is easier to put in and take out a panel. By holding onto the panel and advancing one screw until it just kisses, there's enough tension to hold the panel in place. Then advance the other screw to lock it all in. An important aspect, though, is to have the curve end at the screws and let the portion outside the screws remain straight. Otherwise it would be difficult to clamp panels that are wider than your between-screws distance.

Here's a pic showing the curved caul distributing pressure from the inside out:

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These modifications are real easy to make.

The third screw can be installed in one of two ways. The first way is shown in the pictures. Bore a through-hole for the screw and use bolts to attach the female threaded portion to the outside of the vise. Just make sure to counter-bore the bolt holes on the interior. The second way is to mortise out a recess for the female threaded portion so that it sits on the inside. This configuration would have a cleaner look, but is more work. A stabilizer dowel must also be added. This dowel, which is glued into the "shoulder vise's" face moves in and out of a through hole in the twin-screw vise. If you don't add this, as you advance the third screw, the face will simply rotate and fall off. (Don't ask me how I know that.) (The pictures don't show this, but I wanted to center the vise over the leg, so that the drawer component piece would have more support. But it was an afterthought.)

The curved face drops off about a 1/4" from center to the screws and then remains 1/4" from the center to the ends of the vise. To mark out the curve, simply draw a mark 1/4" down at the screws and draw a gentle curve by hand or by using one of those sweeping curve templates. Then draw a straight line out to the end. Using a bandsaw, cut just outside the line and then plane cross-grain until you hit the line. I used a scrub plane followed by a block plane. You'll want to use narrow planes to get down in the intersection where it turns from curved to straight.

The last modification I made which I haven't mentioned yet, since it would have made my title longer, is to chamfer (a LARGE chamfer) the front and sides. Not only does this make the vise look a little less clunky, it provides a relief when you are sawing half-blind dovetails at a 45 degree angle.