Dovetail joinery is a wonderful fusion of strength and beauty that is a traditional hallmark of quality craftsmanship. Though most woodworkers would like to master this primary casework joint, it is all too easy to lose control of the process, leading to disappointing results, often without really understanding why.
The good news is that you can make excellent dovetails joints of which you will be proud by attending to two important matters. First, understand each step along the way - no secrets, no mysteries. Second, realize where are the critical junctures in the process that determine success, and how to control them to avoid errors.
In this series of posts, I will take you through the process of making a through dovetail joint. The principles and skills will apply to all of the many variations of the joint, such as half-blind dovetails.
The tools you will need
Let's start with an overview of the tools, then in upcoming posts, as we go through the steps of making the joint, their uses will become clearer.
To mark out the tails, a sliding bevel can be used along with a square. However, this method is tedious and less accurate than using dedicated markers. In the photo below are four shop-made markers, each with a different slope ratio, 1:8, 1:7, 1:6, and 1:5. As we will see later, they allow the square line across the end of the board and the slope line on the side of the board to be made at the same time with a single positioning of the tool. Similar markers are commercially available. A 0.5mm lead pencil makes a more consistent line than a wooden pencil.
To gauge the cross-grain baselines, a cutting gauge is necessary. The photo shows two different types, a popular wheel knife gauge on the left, and a Japanese model on the right. Each has two key features. First, it is a knife edge that cuts the gauge line. A single point marking gauge would make a fuzzy, torn line, leaving no hope of an accurate joint. Second, the knife edge is at the end of the stem where you can see it as it cuts the wood, leaving no doubt as to the depth and placement of the line.
A Japanese dozuki (at top in the photo) or a Western backsaw, should have rip teeth for dovetail work. That is, the cutting edges of the teeth are approximately perpendicular to the length of the saw as shown in the close-up photo below. A common error is to use a crosscut Japanese dozuki saw, which will be slow and inaccurate for this task.
My rip dozuki has a 240mm blade with 19 teeth per inch (tpi). My Western dovetail saw, which I now prefer over the dozuki, has a 10" blade with 16 tpi. Both of these types of saws work well, so it is a matter of personal preference.
A coping saw (on the left in the photo) is useful for removing the bulk of the waste, as some woodworkers prefer to do before chiseling to the baseline. I now prefer a high quality fret saw for this task because the thin blade easily fits in the kerf and can be turned to saw horizontally in one step.
Chisels and knives
Of course, you will need a set of chisels and a mallet. The classic joiner's mallet is shown here along with my preference, a small 14-ounce brass mallet that packs a surprisingly strong punch. A basic chisel set with 1/4, 3/8, 1/2, and 3/4 inch sizes will suffice for most work.
The design of the sides of the chisel is important. A chisel with tall, square sides will inevitably hack into the tails as you clear the waste wood between them. There are several solutions to this: one is a Japanese chisel that has sides beveled at 12-15°, as shown below. Western chisels that have a very thin square land below the main side bevel also work well. You want the sides of the chisel to clear the sides of the tails as you chop. This is not an issue when chopping pins so it is important only in the smaller chisel sizes.
A critical step in making dovetails is marking out the pins from the tails. Most woodworkers use a thin single-bevel knife, such as the V-point knife in the middle of the photo below. I use a chip carving knife (at top in the photo) sharpened to a single broad bevel on each side for fine-pore woods, such as pear wood, where the knife line is readily visible. For most woods, I prefer a simple point scriber, seen at the bottom of the photo.
I will mention here the importance of having accurately square edges on the work pieces. Unless you have a perfectly accurate and consistent power tool method of producing this, such as a well-tuned table saw equipped with an excellent miter gauge or crosscut sled, you'll want to have a shooting board to make fine adjustments. More on this in a later post, but I think it is essential for quality work.
The bulk of your investment will be in a good dovetail saw and set of chisels. Woodworking seems to produce a lot of questions and uncertainty in choosing tools.
In our next installment of this series, we'll walk through the process of marking out the joint.