Back in the March 2017 issue of Stumpy Nubs Woodworking Journal, which you can check out for free in the archives, we built a simple clamp-on jig for cutting dovetails with a small router. The jig is easy to make, and the best part about it, besides being a lot cheaper than commercially made jigs, is that the dovetails look like they were hand-cut. In a previous video we used it to cut traditional through-dovetails. This time, we'll use the jig to make half-blind dovetails, such as you would use on drawers, which also look like they were cut by hand.
Watch the video...
...or read the article.
A dovetail joint is made up of a "pins" half and a "tails" half. This jig requires the tails half to be cut first. There are a lot of ways to lay them out. In fact, we recently made a video with some dovetail joint layout tips if you'd like more details. For now, I'm just going to go thorough it quickly so we can get to the actual cutting.
In a traditional through-dovetail joint, the tails would be as long as the mating workpiece is thick. But a half-blind dovetail has material covering the ends of the tails. So, the tails must be made shorter, or offset.
I use a shim to do this. I lay what will later become the pins board on the benchtop, and at the end I place a 1/4" thick shim. On this I stand my tails board, and use a sharp pencil to mark the thickness of the pins board across its face. That shim created the offset I needed to make this a half-blind dovetail joint. Hold onto it, you'll need it again later. For now, let's lay out the actual tails.
You may lay out as many as I like. For this video I was working on two joints, one with three tails and one with four. Again, there's more information about layout in that separate video. The angles of my tails aren't that important, just somewhere between 7 and 18 degrees. Traditionally a steeper angle was used for hardwoods and a shallower angle for softwoods.
The tails half of the joint isn't actually cut with a jig because tails are easy to cut freehand with a band saw, scroll saw, or even a jig or saber saw. Just cut away the little triangles of waste between each tail. You don't have to get too stressed out about this step. If you overshoot one of your layout lines and change the size or angle of one of the tails, you can make up for it when you cut the pins half of the joint with the jig later. Just try to keep your cuts reasonably straight.
What is important is the line across the face of the workpiece, the one we used the shim to draw earlier. That's your shoulder line and it is critical that you don't cut past it. I usually just get close to it with the saw, nibbling away the waste and leaving a jagged edge. Then I use a chisel to carefully trim back to the line without going over. If you do go over the shoulder line, you will have ugly gaps in your joints. Don't do that.
That's it for the tails half of the joint. Pretty easy, eh? Now comes the harder part. In fact, with half-blind dovetails, the pins half is by far the most difficult because you not only have compound angles to cut, but the sockets must be cut to a precise depth. And while the shapes of your tails weren't critical, the pins now must precisely match whatever shapes you ended up with. Don't worry, this new jig will make it a lot easier.
But first, we must trace the tails onto the pins board. I use that same shim as before to set the end of the tails board back from the face of the pins board, which is in my vise. The shim lays against the end of the tails, and I use my finger to be sure it is flush with what will be the outer face of my pins board. Now all you have to do is keep everything still while you trace each tail onto the end grain of the pins board. (If the gaps between the tails are tight, you may not be able to use a pencil. A knife may be a better tool, or even a chisel.)
If you're having trouble keeping your workpieces still as you trace the tails, you can use the shallow rabbet trick, which is discussed our separate layout video. Now let's get cutting.
I use a 1/4" router bit, which I set to the thickness of my tails board. Then I place my pins board in a vise with what will be the outer face toward me. The jig slips over the end of the pins board, and a 1" wide strip of scrap wood slips into the rabbet on the side nearest me. If you were cutting through-dovetails, that strip would prevent chip-out. In this case, it just makes it easier to align the jig flush with the top of the workpiece before you tighten it in place.
The router sits atop the jig, on the end of your pins board, and it's just a matter of cutting away the waste areas between each pin. You'll work free-hand, which may be intimidating at first, but it really isn't difficult. Just remove a small amount of material at a time. Stay away from your layout lines at first, then after most of the waste is gone, go back and get closer to the lines. It's easier to control the router when you only have a tiny bit or material to shave away. Leave the pencil or knife lines themselves in place, though. If you rout them away the joint will be too loose. In fact, you may even leave a little bit of material next to the line. Then you can go in with a chisel and remove the rest by hand while checking the fit of the joint. (At the very least, you'll have to chisel away the rounded corners left by the bit.)
Chisel work should also be done sparingly. Remove a little bit of waste, then check the joint’s fit. Remove more and re-check. A well-fitting, good looking joint is a labor of love and patience. You may wonder if the extra work is worth it, when a commercially made jig will whip out half-blind dovetail joints with no chisel work required. Believe me, the effort pays off in a joint which looks remarkably better than anything you could make with most commercial jigs.
Be very careful using a mallet to assemble a joint like this. It is easy to split the corners near the outer half-pins, especially if the half-pins are very narrow. (For this reason, it may be best for the outer, half-pins to be at least ¼” wide at their narrowest points. However, I like the look of extra-narrow half-pins.)
If you have some fine gaps when you're finished, don't despair! There are ways to fix them. But that's the subject of a future video.
Be sure to subscribe to Stumpy Nubs Woodworking Journal so you don't miss that, or any of the other tutorials we make. And if you visit the homemade tools section of our website, you will find plans for the jig in this video, as well as another dovetail jig for the router table. Happy half-blinding!
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