Dovetail layout is an important part of making dovetails. Dovetails retain their strength as a joint, regardless of look, but one of the reasons for using dovetails is to show them off.
This article is about how to layout dovetails and prep for cutting them. The first step is the milling process. The trickier the joinery the more important it is to have stock that is properly milled. Dovetails are a lot easier if your wood is square, flat and all the same thickness. Tend to that first.
The next step is to organize your tools. For hand cut dovetails you will need a small square, a marking gauge, an angle gauge, a couple chisels, a mallet and a saw. You also need either a sharp pencil or a marking knife.
It makes all the difference if your tools are sharp. So get everything nice and sharp - that includes the marking knife and/or pencil.
Now, you're ready to begin your dovetail layout. It's worth thinking about this step a bit. It makes a difference which board has the pins and which has the tails. If you look at a dovetail joint you will see that there is only one way to take it apart.
You can pull the pin out vertically, but the tails lock the pin in place if you pull horizontally. This makes the joint stronger in one direction than another.
You should keep this this difference in strength in mind when deciding where to put the pins and where the tails of your dovetails. If you are making a drawer for instance, you want to have the pins on your front and back, because the pressure will come from pulling the drawer open, not from the sides.
Layout your dovetails in such a way that they are symmetrical, but not boring. The thinner the pins the more elegant the look. The dovetails in the photo to the left were cut by hand. The ones on the right were done with a jig.
Often jigs don't allow for any dovetail layout, rather they are set in a fixed position. That is one of the advantages of cutting your own. You can layout the pins and tails any way you like.
You can make your pins and tails the same size, or the pins can be smaller. Of course, they don't all have to be the same size across the board, nor do they have to be evenly spaced.
In any case start with a half pin (which doesn't have to be half size, but rather has one flat side on the edge of the board. Layout the remaining pins any way you like. I usually start with a 1:5 or 1:6 ration for the angle, and then change it to whatever I think looks good.
Tip: if you want to find the correct angle, draw a line 6" (or 8") high, then make a mark one inch beside the base. Now you have a triangle with the correct ration Six up, one over = 6:1 (and you thought you'd never use the math you learned in high school).
It's helpful to keep your tools in mind when choosing your dovetail layout. It's tough to get into an area that is thinner than your smallest chisel, for instance. Drawer your layout on paper until you get the look you like, then transfer it to your board.
Here's a tip for dividing your wood into even sections. Slant a ruler across the board so that the ends are on even numbers. Then you simply mark your points.
As you can see, in the photo the ruler is laid out so that zero is on one corner and four is on the other. I marked my lines at 1", 2" and 3". Those marks are all equidistant from each other. I use a square to carry each mark to the top of the board and mark off the pins from those checks. Getting even spacing is often the most difficult part of dovetail layout and this trick makes it much easier.
For more information on dovetails and other woodworking joinery see the following pages: