In many ways, 2017 has been the year of the dovetail. In the January issue of Stumpy Nubs Woodworking Journal, I showed you a cool router table sled for creating flawless dovetails that look hand-cut. In the March issue we featured another clever jig that clamps onto the end of a workpiece for cutting dovetails with a hand held router. And in the June issue was a dovetail jig for the table saw. You can find more information about all these jigs in the back-issue archives, or at the links in the notes at the bottom of this page. Today we'll address a skill you'll need, no matter which of the jigs you use.
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If you want a dovetail joint to look hand-cut, you must lay it out properly. Machine cut dovetails are easy to identify because the pins are typically at least as wide as the 1/4" shank of the router bit, and they are usually evenly spaced and sized. Some of the expensive jigs on the market allow you more freedom, but with careful layout and a cheap, homemade jig, you can make a machined joint look like it was cut by hand, with very little skill or practice. Today I'll show you a fast and easy way to lay out both traditional through-dovetails, and half-blind dovetails for drawers. You can then use this information with any of the easy to make jigs on our website.
A dovetail joint is made up of two halves. You have a “pins” side and a “tails” side, which must cut separately. Some people like to cut the pins half first, others like to start with the tails. I'm going to show you how to do a pins-first layout for through-dovetails, and then a tails-first layout for half-blind dovetails.
Begin by marking the tails board with a T and the pins board with a P on what will be the outer faces in the assembled joint. This will help you keep track of things as you work.
Stand your tails board on its end, and butt your pins board against it. Use a knife or very sharp pencil to mark the thickness of the pins board on all four faces of the tails board. Then swap the boards, this time marking the thickness of the tails board on the front and back face of the pins board.
Next, clamp the pins board in the vise with the P facing toward you, and use a pencil to place marks on the end-grain about 1/4" from each of the two edges. These are your half pins- We're going to ignore them for the moment and work on dividing the larger space in the middle.
A THROUGH-DOVETAIL JOINT
Place a mark near the center, dividing the big section into two medium-sized sections. Then divide each of those in half so you have four smaller sections. All of this can be done by eye.
Now place marks about 1/8" from each of the three new dividing lines. These three pairs of marks indicate the locations of your full pins. Yes, I know the full pins are narrower than the half-pins on the corners. The name "half-pin" refers to half the shape, not necessarily half the size.
If you are using a jig with a fixed fence angle, like the router table dovetail jig, or the table saw sled dovetail jig, set a bevel gauge to the angle of that fence. Otherwise choose and angle between 7 and 15 degrees. Traditionally shallower angles were used for soft woods, and steeper angles for hard woods. But really, it's a matter of taste.
Place the blade of your bevel gauge on the line next to half-pin on the left corner of the workpiece, and strike a line, angling to the right. Then move across the end of the workpiece, striking similar lines on the right side of each of the pairs of full-pin marks.
Next, flip the gauge and work your way back in the other direction, drawing lines from the left side of each pin, angling to the left.
Use a square to carry those lines down both faces of the workpiece, stopping at the thickness lines you drew across the face earlier. Finally, draw an “X” or scribble out the waste areas between each pin so you don't cut in the wrong place. Believe me, it happens!
These three full pins and two half pins are plenty for most workpieces. But if your workpieces are really wide, like over 10-inches, you may want to divide them even further by splitting each of those four sections into eight, and so on. Of course, you don't have evenly space them at all. In fact, variably spaced pins can give a joint a look that really sets it apart from obviously machined joints. We'll try that with a half-blind joint layout shortly.
Cut the pins using your preferred method. (I prefer the band saw.) If you make any small errors, such as cutting over one of your layout lines, don't worry about it, because you will be cutting the tails half of the joint to match, so you can cover up any errors.
Before you can cut the tails half of the joint, you first must transfer the shapes of your pins to your tails board. Place your tails board with the T facing the bench top. Stand your pins on the end with the face marked with a P facing you. Then use a knife or very sharp pencil to trace each pin. Be very careful that nothing moves while you do this. That's vital if you want your joint to turn out. And don't forget to mark off the waste areas between each tail.
Here you can see why I like to cut the pins first. It's easy to get your pencil between them to trace their shapes onto the tails board than it is to do it the other way around. Just be sure your pencil is nice and sharp, so your lines are accurate.
One way you may cheat to keep the pins or tails boards from moving as you trace is by cutting a very shallow rabbet on the end of your tails board. (On the inside face.) The ends of your pins will sit inside that rabbet, keeping everything aligned and preventing movement as you trace them.
That's it for laying out traditional through-dovetails. In the notes at the bottom of this page you'll find links to some videos about ways to cut the tails with a router or a table saw. Now, let's move on to the more challenging half-blind dovetail joint layout. If you are cutting half-blind dovetails, especially with the clamp-on jig we featured in the January 2018 issue of Stumpy Nubs Woodworking Journal, you must do things slightly differently.
A HALF-BLIND DOVETAIL JOINT
When you mark the thickness of the pins board on the face of the tails board, place a shim beneath the end of the tails board to raise it up about 1/4". This will give you the offset needed to make it a half-blind dovetail. You only raise the tails board in this way, you don't to do it when marking a thickness line on the pins board.
This time, we're laying out the tails first, rather than the pins, because that's what the jig I like to use requires. I still do this by eye, beginning with the two half pins near the outer corners. But this time I am putting one tail in the center, which I indicate with a pair of marks, about 1/8" apart on each side of where I want that center tail.
Next, I use a bevel gauge or a dovetail angle-marker to carry the lines down the face of my workpiece to the shoulder line. I'll end up with three tails, which is plenty for almost any drawer. You may notice that I didn't divide the joint evenly. The narrower center tail adds visual interest and lends to the hand cut look of the joint. You can do this with through-dovetail joints as well.
As always, I like to cut the tails half of any dovetail joint on a band saw. Then I can transfer their shapes to the end of my pins board. The easiest way to do that is to cut a shallow rabbet on the back of the tails, just like the rabbet we discussed earlier. This will slip nicely over the end of the pins board, keeping everything aligned as you trace the tails. As a bonus, it also will make it easy to offset the tails board the proper amount from the outer face of the pins board. If you don't want to cut a rabbet, you can use the same shim you used earlier to set the offset. Just place it against the ends of your tails and flush it up with the face of the pins board.
The biggest problem with tracing the tails is the small gaps between them makes it difficult to fit a pencil inside. In this case a knife, or even a chisel would be a better tool. Make sure you mark them accurately; the success of your joint depends upon it!
We created separate video about cutting half-blind dovetails with an easy to make, clamp on jig. If you'd like to see how to cut through-dovetails with a router or a table saw, check out those links below. Be sure to check out the latest issue of Stumpy Nubs Woodworking Journal, it's always filled with great tips, tricks and tutorials designed to make you a better woodworker. You can read and subscribe for free at stumpynubs.com. Happy layout!
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