Dovetails.
A byword for carpentry perfection. Mastering them has long been considered a rite of passage for those reaching the heights of woodworking excellence. They are also a very strong means to join two pieces of wood together at right angle, with an attractive flourish to finish that will earn the admiration of any who take a glance. To aid you on your quest for dovetail perfection, David Barron takes us through this step-by-step guide to creating a dovetail alignment board, using dovetails! He also includes some of his own techniques for achieving accuracy with detailed cuts.
What is a dovetail alignment board?
A dovetail alignment board is effectively a jig for marking up the two components of the joint – known as dovetails and pins – with pinpoint accuracy. For example, if when marking up your aligning cuts, your wood moves, the reference fence ensures that you can realign the two boards exactly as before. As such, a dovetail alignment board is a worthy addition to any workshop.
David continues…
The secret to clean, crisp joinery is maintaining accuracy at every stage of the process. My latest alignment board is designed to keep your layout lines exactly where they need to be; on the straight and narrow. For this project, I’m using twisted dovetails to show you how to make my dovetail alignment board. This board allows you to line up the bottom edges of your work against the fence of your router table, so that the grooves for the box or drawer base will also line up. It also keeps things square, so that the finished drawer or box sits level. Of course, in order for the alignment board to work well it needs to be made extremely accurately. Refer to the below exploded diagram for dimensions.
Making a dovetail alignment board
Preparing the stock
It is best to use quartersawn timber. This gives long-term stability, and using a single board will allow both pieces to move in harmony. In this case I’m using some nice quartersawn elm (Ulmus procera). It’s very important that the cut of the two main pieces is exactly at 90°. I use the table saw for this. By flipping one board against a straightedge, any error is doubled and clearly visible. Shim as necessary until you have a perfect 90° on both pieces.
Marking and cutting the dovetails
With the parts prepared and marked with dots, it’s time to look at the dovetails. I’m lucky enough to own the joint that Alan Peters used in his article for Fine Woodworking back in November/December 1986, and I chose to copy his spacing and layout. The spacing between the tails on the baseline of both boards is even, making the joint look balanced. Having said that, the possibilities and layouts for this joint are endless, and experimenting with different layouts can give some rewarding results.
Cutting the tails
Cutting the tails requires concentration, as the front and back angles need to be cut at the same time. I find it best to do this with the saw at 45° to the corner, nibbling away gently to get things just right with both lines. Make sure you take your time. Once on track, the cut should continue smoothly. I removed the bulk of waste with a fretsaw – taking it as close to the line as you dare, with the remainder being chiselled out. I found the elm very soft with a tendency to collapse, so I made sure my chisels were razor sharp.
Marking the pins
With the tails cut and cleaned out, it’s time to look at marking the pins. In Alan Peters’ article he marks out both parts of the joint in advance and simply cuts to the pencil lines. I prefer David Charlesworth’s method in his excellent book Furniture-making Techniques. He marks the pins from the tails after they have been cut out. It’s best to use a knife rather than a pencil – I find this much more accurate. The actual marking needs to be done with one board directly on top of the other. Make sure these are flush on their edges as well as faces. I found it best to clamp them up and make fine adjustments with a brass hammer – you can use a mallet or something with a bit of weight behind it. With a final tighten on the clamps and a check with a straightedge, I secured the whole thing in a vice which made the actual marking easy. I finished marking the pins with a knife on the face side, and then cut the pins using the same technique as the tails.
Assembling the joint
After checking the fit, now the exciting part! Now to assemble the joint, which needs to bring both pieces of wood together simultaneously at a 45° angle. Both Alan Peters and David Charlesworth used a combination of cauls and clamps on both sides to gradually pull the joint together – a slow-setting glue, such as PVA, is definitely helpful here. Instead, I used a more low-tech method – a dead blow mallet and a block of wood! This is equally effective for disassembly if needed. I alternated from one side to the other, making sure to keep things square, and it went together without too much trouble.
It’s important to make sure the joint closes without gaps on both baselines, otherwise they will not sit at a perfect 90°. To aid this process you can undercut the end grain when cleaning out the tails and pins. With a final check to make sure the two pieces are at 90° to each other, leave the board overnight to set.
Adding the fences
After planing the surfaces and edges – being careful to keep them flat – it’s time to choose which side the fences are going to be mounted. With the board on its edge on a dead flat surface, take a square and check to see if the corner is square with the surface. Do this from both sides and on both edges to see which is the best. If any adjustment is needed on the better of the two sides, this can be done by carefully shimming the fence with veneer.
Before attaching the fence, apply a chamfer to the inside edges. This acts as a dust groove to prevent any debris from giving a false reading when the board is in use. The fence should protrude about 4mm above the surface of the board. Screw it into place, rather than glue, so it can be shimmed as mentioned above.
Summary
As many woodworkers will attest, dovetail joints are intricate and complex, with barely any tolerance or room for error. Yet they are often a necessary detail in woodwork. A dovetail alignment board is a superb tool to ensure that your measurements are accurate every time. This brilliant jig is a fun and rewarding way to further develop your woodworking skills. What’s more, with this example, you can further practice your dovetail making!