A good twin screw vise can do many tasks. When clamped to the edge of a bench top, it can be used as a proper face vise for dovetailing or other joinery. Sitting free on a bench top, it can restrain an assembly for driving wedges or be a third hand for safely splitting tenons. In a pinch, it can even take the place of a machinist vise for basic metalworking (although I would recommend vacuuming it off when you’re done, as metal shavings are anathema to woodworking tools).
But a good twin screw vise doesn’t have to cost a fortune. I mean, it can, if that’s what you’re into (with wooden screws or prefab hardware and whatnot). But it doesn’t have to. In fact, all it really takes is about US$13 worth of home center hardware and some off cuts.
There are two typical ways to make a vise screw work without a garter that attaches the movable jaw directly to the screw. You can affix the screw to the back jaw, and turn a nut to sock down on the moving jaw. Like the Benchcrafted Moxon Vise. Or you can affix the nut to the back jaw and use the screw hub to sock down on the moving jaw. Like the Lake Erie Moxon Vise. For this, let’s do the latter. There is a third way, which I’ll cover briefly below.
Start with the front jaw. Now I am sure there are people who can use a brace and bit and drill a perfectly perpendicular hole. But I can’t, so I used the drill press. The screw should be relatively snug in the hole (phrasing?). This threaded rod is about 3/4″ and a 3/4″ forstner bit was just tight enough. Inset the holes at least 1 1/2″ from the ends of the front jaw for strength. Some people elongate their holes to permit clamping irregular work. I don’t.
It’s super important when making a twin screw vise that the holes line up. So clamp the front jaw to the back jaw and use the same drill bit to transfer the center of the hole into the back jaw. I should mention that the back jaw is about 4″ longer than the front jaw for some clearance each end when clamping to the bench. Otherwise, the clamps get in the way of the work.
After you’ve bored the hole in the back jaw, put both jaws back together, insert the threaded rod, tighten up a nut on both sides of the jaws and trace around the nut on the back jaw with a marking knife. Then chop down to the lines about three fourths of the height of the nut. Repeat for the other nut and use a small bit of epoxy to affix the nuts to the back jaw.
Balance is an important part of any twin screw vise. Even with the narrower front jaw, it’s likely the vise won’t balance itself with the front jaw hanging completely off the bench. So I typically add an extension to the back jaw flush to the work surface. It adds weight and stability and is a convenient place to put down your pencil or marking knife when cutting joints. Glue should be all you need, but maybe add a screw or two through the inner jaw to make sure everything stays put long term.
When the glue dries, you’ll have a functional vise. There is something called a “rod coupling nut” which is really just an elongated nut. You could use a couple of these as floating hubs and the vise would work just fine. It wouldn’t be super comfortable (you’d have to turn the threaded rod by hand) and the nuts would wear into the front jaw over time, but it will hold. Want proof?
You could also affix one of those rod coupling nuts to the end of each threaded rod and also be done. But I like wooden screw hubs, so let’s do that. Start with square stock and drill into the end of the hub. I used the drill press, but you could do this by hand. Just clamp the work across all faces to prevent splitting.
I think it took more time wedging underneath the benchtop to get it perfectly level in all directions than it took for the epoxy to set. Be careful not to make too much of a mess, but excess epoxy can be used to reinforce the end grain of the hub (that wears against the face grain of the outer jaw). When the epoxy was set, I drilled through the hub across the grain and pinned through the threaded rod with a 1/8″ steel rod (fixed with superglue). Probably not necessary, but who knows what that zinc coating will do long term?
Then shape the hubs as you see fit. I put a small chamfer on each corner of the hub for starts. I have a feeling it’ll get down to roughly octagonal by the time it’s done. I don’t like round hubs.
And that’s it. Clamp it to your workbench and have at some joinery. Maybe add a coat of penetrating oil finish to all surfaces other than the inside faces of the jaws. I may glue some leather to the outer jaw to increase grip, but it’s not strictly necessary.
If you’ve never made a vise before, this is a good way to figure it out.
I am, at this point, nearing US$100 into the low plywood workbench project, but it feel like it’s pretty much done. I need to bore a few more holes in the bench top (and make a few more dogs) but that’s more planning than labor.
After undertaking this experiment, I have some thoughts. But first, now that the vise is done, it’s time to make a little tool chest on this workbench!