Dovetails on a Tablesaw: Making a bench seat
Above: Made from red cedar and silver ash, the author’s bench seat is 1030 x 370 x 450mm high and features machine cut dovetails and curved ends.
Words and process photos: Peter Young
My personal preference is to cut dovetails by hand, whether it is for drawers, boxes or bench seats. I like the look of the handcut joint and also the freedom it gives me in layout and design. But there are times when I use the tablesaw to do the job, as is the case with this bench seat which has quite thick components. The method is also useful where you need to do a number of dovetail drawer boxes of similar size for example.
Angles and sizes
To cut the tails, the sawblade needs to be angled, while for the tails the work needs to be angled. Commonly used dovetail angles are 7° (1:8), 9.5° (1:6) or 14° (1:4). My approach is to use lower angles for wider stock and bigger angles for narrow stock. So for a 22mm drawer front I routinely use 1:8 ratio but for a 6mm tray inside a box I would use 1:4. For this project I am going to use 7° or about a 1:8 ratio.
Jigs and fences
Two jigs are required, one for cutting tails and the other for cutting the pins. The details of the jigs vary a little depending on the type of tablesaw you are using. For the tails jig on a standard tablesaw you need to make a crosscut sled (see Andy Groeneweld’s article in AWR#98).
For a saw with a sliding table, as shown in the article, the jig is L-shaped and is clamped to the crosscut fence (photo 1).
For the pins jig, the work needs to be presented to the blade at the same angle as the dovetails, in this case 7°. Two angled fences are required, one to cut each side of the pins (photo 2).
Cutting the tails
I lay out the tails on the leg components using a black marker for clarity and working from the centre line outwards. If I’m making several dovetailed boxes or drawers I only need to mark up one drawer side and then I use a stop block to make the same cut on each of the other sides.
A rip blade is used to make the cuts but as it is at a 7° angle the base line is not square and some cleaning up will be required, so I adjust the height of the blade so that it cuts 1–2mm below the base line (photos 3, 4).
If you are using the tablesaw method often it is worthwhile using a dedicated rip blade with the top of the teeth re-ground to 7°. This produces a nice clean cut and you can set the depth of cut right on the base line (photos 5, 6).
With a 7° angle and 10mm pins there is only a small triangle of material left to clean up by hand (photo 7).
Cutting the tails in the legs of the bench is fairly straightforward. Using a digital protractor set the blade to 7°, and then cut to the layout line. Starting at the half pins, make a cut on the waste side of the line. Now flip the piece and make the same cut on the other end of the same board. Repeat with the other leg. Now go back to the first leg and make the next cut, then repeat the procedure until all the joints are cut.
Cutting the pins
Now you need to transfer the tail layout to the pin board. On large components like the bench, I like to clamp a baton on the baseline on the inside of the tail board (photo 8).
With the tail board supported so that it is at the same height as the pin board held vertically in the vice, it is now a straightforward matter of transferring the layout to the end of the pin board (photos 9, 10).
Theoretically, all the components should be the same, so it should only be necessary to mark out one tail board and use it to set up for all the other cuts. In practice it is safer to individually transfer the tail layout to each pin board.
Make a test cut on an offcut to make sure that the blade is at the correct height (photo 11).
One side of the tails jig is used to cut one side of the tails, then turn the jig around to cut the other side of the pins (photos 12, 13). Use a rip blade with the teeth square at the top and the position the blade vertically.
As with handcut dovetails, some paring may be required to fit the pins accurately to the tails (photo 14) but with practice and knowing how close to cut to the layout lines the amount of paring can be minimised.
Cutting the curves
Now that the dovetails have been cut for the bench seat, the legs can be shaped to a curve (photo 15).
I was unable to do this with my bandsaw, so I removed the bulk of the waste by clamping the leg to a right angle fence attached to the sliding table of the tablesaw and the blade angled to a tangent of the curve (photo 16).
The remainder of the curve was produced using handplanes and cabinet scrapers (photo 17).
For this bench project, the main advantage of cutting the dovetails on the tablesaw was the ability to handle the quite large components with ease. Similar advantages would apply to large carcase components.
For smaller components such as drawers, the main advantages are the relative speed of cutting out the tails and pins, especially if all the drawers are the same size and there is no need to lay out the cutting lines for each individual drawer. It is also possible to cut quite small pins and this is helped by having a narrow kerf blade reground to the appropriate angle, in this case 7°. Another advantage is the ability to vary the space between pins. A disadvantage over say router jig methods is that individual fitting of the joints may be required.
So, while I do not use the tablesaw method frequently, it is a good technique for certain circumstances, and this bench seat is a good example.
Peter Young is a studio furniture designer and maker who lives in Brisbane. Peter teaches at Sturt School for Wood and sometimes other woodworking schools. He is a regular contributor to Australian Wood Review magazine.