When starting a new box, I try to use a technique that will both expand my skills and give the project a bit of interest. In this case, I wanted to build a box with a sliding lid, and I wanted the top of the sides to remain intact. This meant that the lid would have to slide through the sides of the box. Designing the sliding lid in this way liberated me to profile the top edges of the sides on an angle. This led me to the mitred dovetail.
Mitred dovetails have roughly the same mechanical strength as a regular dovetail, but differ in one important aspect; they allow an edge to be shaped without interruption.
I prepared the stock in such a way that the grain flows all the way around the four sides. I rough-milled the maple, let it settle, and then milled to my final dimension. Before starting to work on the joint, I pre-surfaced the inside faces of the sides. This is a very important step for all dovetailing work, as doing any surface prep after the dovetail is cut will loosen the joint.
Making a mitred dovetail joint is almost the same as a regular dovetail, with two key things to remember. First off, don’t scribe the top and bottom edges of your pieces with your marking gauge.
These will be scribed with a combination square and a knife. Secondly, and most importantly, you need to remember to keep some of what is usually waste when you get around to cutting the tails.
Once your scribe has been set to slightly more than the thickness of the sides, scribe the faces of your work pieces. Allowing the pins and tails to protrude a bit will allow some grain consolidation, if needed. Don’t scribe the top and bottom edges with your marking gauge. Instead, use a combination square and a knife to scribe a 45º angle towards the outside corner of the joint. This is the mitred portion of the dovetail. Proceed with the layout of the pins with a pencil and a small bevel gauge.
Once the pins are laid out, cut them with your favourite saw. I prefer a Zona saw for the cheeks and a coping saw to get rid of most of the waste. Once the pins are cut, I place the piece in a chopping block. It is critical that the chopping block is perfectly aligned to the scribe line. I use a wide-plane iron, set in the scribe line, to help with locating the block. Clamp it down and chop to the line.
It’s very important for the pins to be flat and square. To check the flatness, I simply lay the back of my paring chisel on the cheek of the pin, and check for rocking. When I find a high spot, I carefully pare it down. To check for square, I use a narrow brass blade that I made for a small square. The pins need to be square to the end grain of the work piece. Getting the pins just right is the most important part of dovetailing. Any discrepancies that are left in the pins will make getting a proper fit on the tails exceedingly challenging, if not impossible.
Once I’m satisfied that my pins are all proper, I transfer the layout to the tails. Here is where things diverge from a regular dovetail. It is critical to not cut all the way through the outside tails. This section of waste needs to be mitred. I do this first, so that I don’t forget. The center section of tails gets the regular treatment.
We need a 45° hardwood ramp in order to cut our mitre. I usually cut the ramp then shoot it with a block plane, making sure that it is exactly 45° and straight. It can be helpful to use a ramp that is about an inch wider then your sides. The extra material then overhangs and provides you with a better platform for your chisel. Lining up the ramp with your scribe line can be a little tricky. Before you commit to removing the material, double-check that everything is lining up properly. You can do this by laying a ruler on the ramp and checking your 45° scribe line. Adjust if necessary. Once all of your mitres are shot, proceed with fitting the tails to the pins.
Now that the joint is perfectly fit, the profiling of the top can take place. Use layout lines to keep the profile consistent to give a seamless transition from one side to the other. Before gluing the joint, I size the mitres. This consists of applying some watered-down glue to the end grain and letting it dry. Once this is done, the joint can be assembled.
Don’t Scribe the Sides
Use a combination square to carefully mark a 45º angle on the sides of each piece.
Breau uses a wooden board with a square edge clamped to the workpiece to help guide his chisel squarely into the joint. First he places the bottom of the chisel against the wood guide and pares the base of the dovetail joint (above), then he rotates the chisel so its side is against the wood guide, which assists with cutting the face of the pin (below)
Cut the Mitre
With a fine handsaw, Breau rough cuts the mitred edges on the ‘tails’ portion the dovetail joint.
Ramp It Up
A 45° ramp is used to guide the chisel while making the paring cuts on the corners. The ramp must be positioned carefully before it’s clamped, but works wonders once it’s in place.
Ready for Assembly
The mitred dovetail joint, viewed from the inside, just before assembly.