Dovetailed Clock and Letter Rack
Wednesday 17 August 2011
Michael Forster reckons it is time for a tidy up
It's not just being a dinosaur that makes me passionate about
hand-skills. There are circumstances where the time taken to set up a machine is just disproportionate to the task in hand.
There are also eventualities when hand-skills might be the only available option - but, most of all, and especially for the leisure woodworker, there is a quiet satisfaction to be had cutting a joint by hand without the dust and noise of machinery.
So here's a little project designed to hone your skills with the dovetail saw and chisel, and then put the results proudly on display.
We've probably all stuck a letter or a bill behind the clock at some time - so why not make it official!
With any precise hand work, good kit is crucial to success. I'll explain the tools generally as we go along, but let's begin with a decent dovetail saw, with rip-pattern teeth so that they'll follow the line and not the grain.
For small joints, my Veritas 20tpi fine dovetail saw is ideal, and a bargain at half the cost of its rivals. If you want to do good dovetails and stay sane, don't use anything less.
Prepare the timber first - for a good contrast, showing off the joint, use something pale for the front and dark for the base.
I used ash, with an unidentified dark timber reclaimed from an old blanket chest. For simplicity, make the front and base of the same thickness so you just only need to set up one gauge.
1. Getting everything flat and square
is essential and a shooting board makes squaring the ends much easier.
For the back, you could cut a second dovetail, but I took the easy route.
A housing is easily cut at the router table, and it's best to do this early so that the upright back piece can be thicknessed to be a good fit. The top surface of the base needs to be cleaned up with a hand plane to a fine finish at this stage, as removing any material from that surface afterwards will loosen the dovetail.
Before going any further, it's a good idea to mark and drill the spindle hole for the clock movement - it's easier to do this at the drill press before the joint is assembled. Next, mark out the joint with a cutting gauge - not a marking gauge with a pin that will tear, but with a blade. Even better are the wheel-type gauges from (in order of cost) Axminster, Veritas and Titemark.
2. Set the gauge to a hair under the thickness and use it to mark the shoulder lines all round the tail board, and just on the broad sides of the pin board.
3. To minimise cleaning up, cut fairly lightly on the front face but deeply on the tail-board edges for the shoulders - this will give a nice, crisp edge to mate with the pin board.
Marking your dovetails
4. Now to mark the tails. I've seen some weird and complex formulae used for this in books and magazine articles - but they're all delightfully unnecessary as all you need for beautifully-proportioned tails and pins is a pair of dividers and a slip of scrap wood about 6mm thick.
This technique works whether you're using just two tails or a hundred and two - saving masses of time and guaranteeing accuracy simultaneously. Incidentally, the term 'half-pins' refers to the profile, not the width. These need to be quite robust to prevent their splaying as the joint is assembled and to give strength to the joint.
5. Using the scrap as a gauge, mark a dot where the half-pins will be from the edge of the timber.
6. Set the dividers by guestimation to about the width of one tail plus one pin.
7. Starting on a half-pin mark, lightly step the dividers across
(here I've gone from right to left) until the point lands just past the other half-pin mark. Keep adjusting and re-trying until this distance is the size you want for your pins.
8. When satisfied, step across, lightly stabbing in, first from one side and then from the other. The overlap will define the tails and pins.
9. The method works perfectly however many tails you're using - two is about right for this project. I've stabbed in a little deeply here for the camera.
10. Place a pencil in the divider mark, slide the saddle up to touch it, and then mark the end and face in one action to minimise inaccuracies.
11. The tails are now ready for cutting. An alternative method for marking up the dovetail faces is to complete the marking out using a square and a bevel set to a one in eight angle, but I prefer my saddle marker.
Saw technique is the key to good dovetails, and is worth practising
anyway for reasons stated earlier. The tail saw cuts must be perfectly square across the end grain or the joint just won't fit well.
12. Use a small spirit level to ensure the timber is level - it really does help my hand to sense the angle.
13. Now cut your dovetail cheeks. I like starting the saw with Rob Cosman's pinch grip - it really does give control. Start with the saw flat on the timber, supporting the saw for the first few strokes, and then allowing the heavy back to push it down. Use the full length of the saw and let the tool do the work. You must start the saw off perfectly aligned with your mark - a good dovetail saw won't have enough play to allow correction in mid-cut and if it did, the joint would be bad anyway.
14. The first strokes should have the saw nicely aligned in both planes - it's worth practising this on scrap. And stop exactly in the line cut with your gauge. Stopping short will just mean more chisel work - and the danger of spoiling the joint - while going past the line will leave an ugly scar For the shoulders, use a similar technique but this time remembering that the cut is going down square to the edge. Again, if in doubt, do some practice cuts first - you're looking to split that deep gauge line, leaving a tiny polished border on the edge of the cut.
15. This can be reduced by cutting out the bulk with a piercing saw, leaving a few millimeters to chop back to the line. A coping saw will be too coarse to fit into the dovetail saw kerf but if that's all you've got, then don't force it in - start another cut in the middle and take out the waste in two cuts.
You'll see pictures of people with the work in the vice paring down to the shoulder-line, but I find this fraught with difficulty in controlling the chisel and maintaining squareness.
My approach is adapted from David Charlesworth, so it's not surprising that it simplifies and makes the operation safer.
16. With the board clamped down on scrap, I sit down on a step-stool to get my eye a little closer to benchtop height. I can now clearly see the angle of the chisel as I chop through halfway from each side, taking very light cuts to avoid letting pressure from the bevel of the chisel push the edge back behind the line.
I set up a square behind the chisel so that I can ensure that I am minutely undercutting to ensure the shoulders can seat down nice and tightly on both sides. I steady my chisel hand by resting my elbow on the bench and for the final cut, the chisel is located by feel in the gauge line. With a sharp chisel, this is a very safe way of cutting precise shoulders for a snug fit.
Now it's time to scribe the pins - and don't even think about a pencil, however sharp! Get a good marking knife for this job and you'll be amazed how often you'll use it for other tasks. I use a Blue Spruce that has a flat side to register against the cheek and a double bevel to let you use it right- or left-handed. The thin blade is essential to get into fine sockets - some otherwise excellent marking knives are too thick for this task.
17. Most books and articles will advise using a plane on its side to rest the tail piece on when marking out the pins - fine for a professional in a hurry, but I prefer to take time cramping the pieces in a simple jig that will ensure nothing moves while I'm marking out.
18. Once the lines are scribed, they can be squared down the face and you're ready to saw.
Again, some practice cuts on scrap will pay dividends. Once you're confident, set the pin board upright in the vice and saw to split the line, leaving a tiny polished border which is one side of the knife-line.
You might feel safer at first leaving more of the line in - you can always pare back with a chisel - and then as you see how the joints are coming out, you can modify your approach over time. Chisel work is essentially similar to the tails, but with a broader chisel and angling the corner cuts to follow the pin profile.
You should now be ready to assemble the joint. Having ensured that there are no obstructions, especially in the corners of the sockets, just tap the tails about halfway home, watching out for any tendency for the half-pins to spread, in which case, some paring is called for.
For glue-up, use a small spatula to spread glue on the surfaces, tap the joint together, wipe off excess glue and wait for it to dry. Then simply flush down the joints with a sharp plane, cleaning up the surfaces as you go, removing all the planer-ripples from the original prep.
19. You are then ready to fit the housing piece at the back too. Glue this in place, ensuring it is parallel to the dovetailed upright with the clock mechanism in place. Next, simply
apply a finish of your choice... a few coats of a Danish oil always brings out the grain nicely. Then fit your clock movement and there you have it - a lovely little clock in which you can also store your mail.
Practice makes perfect
When I first set out to improve my dovetailing, I kept a supply of scrap timber handy and went to my workshop most evenings just to cut a row of practice lines. The technique soon came, and with it the confidence to make more of these, which have gone down very well as presents for family and friends.
So next time you need to make a quick but accurate cut, you won't need to spend time setting up a machine or jig, but will reach for the hand saw with all the confidence of an accomplished woodworker.