How to Make a Dovetail Joint in Woodworking

Dovetail joints are not only beautiful, they’re very strong. Once you know the to cut them, it only takes practice a good fit every time.

Most pieces of wooden furniture are built as either frames or boxes. The mortise and tenon, as the principal framing joint, is common in chairs and tables. But in box construction the dovetail has traditionally reigned supreme.

True, modern storage furniture often uses screws, dowels, assembly fittings, and edge joints cut with power tools But you only have to look at a set of dovetails to see that they make the perfect corner joint between flat timbers such as box sides – including the top and side panels of furniture carcases’.

dovetail joint How to Make a Dovetail Joint in Woodworking

In fact, dovetails are impossible to pull apart. That’s why they’re found joining drawer sides to drawer fronts and sometimes backs. Every time you open a drawer, you’re trying to pull the front off – and the dovetail joint withstands this tendency as no other joint can. Note, however, that it only locks in one direction. If you use it the wrong way round where its strength matters, its unique properties are wasted.

There’s one other major point to remember Chipboard is far too weak a material in which to cut dovetails – although, at a pinch, they’ll work in plywood and good-quality blockboard. The dovetail joint is always admired and even respected. But there’s really no mystery about it. While no one could pretend that well-fitting dovetails are easy for a beginner to cut, the only secret of success is practice; and you’ll find things go a lot more smoothly if you stick closely to the time-tested procedure described here.

Anatomy of a dovetail joint

Dovetails themselves are fan-shaped cutouts in the end of one of the pieces being joined -fan-shaped, that is, when you look at the face of the piece.

The sides of each tail slope along the grain at an angle of between 1 in 5 (for a coarse’ but strong joint, suitable for softwood and man-made boards) and 1 in 8 (generally considered the best-looking, and usually used with hardwoods). If you make them any coarser, they may break; any finer, and they may tend to slip out under strain.

Between the tails, when the joint is assembled, you can see the pins’ cut in the other piece. These, of course, follow exactly the same slope or rake’ as the tails – but across the endgrain, so you can only see their true shape when looking at them end-on. Note that there’s always a pin at either end, this helps to secure both pieces against curling up.

The spacing of the tails is another factor in the joint’s appearance. In general, the wider they are (and therefore the further apart the pins are) the better – but this too affects the strength if you overdo it.

Marking out the tails

The first step in making a dovetail joint is to get the ends of both pieces square (they needn’t be the same thickness) Particularly if it’s your first attempt, you may find it wise to leave a little extra length as well – say a millimetre or two.

After that, it’s customary to start with the tail piece (which is the side, not the front, in the case of a drawer). First decide on the slope of your dovetails say 1 in 6 – and mark it out on a scrap of wood or paper. That’s just a matter of drawing two lines at right angles to each other, then making a mark six units along one, and another mark one unit up the other Join up the marks with a diagonal, and set a sliding bevel to the same slope.

Now you need to work out where each tail should come. However, there’s no need for fiddly calculations. First decide the width of the pin at each end, and square that along the grain. Then place a tape measure diagonally between the squared lines, and swing it round to give a figure easily divisible into equal parts. Mark off these equal divisions, and square them along to the end of the piece. These are the centres of the gaps between your tails

Then make a mark 3mm either side of each centre mark, and draw a line sloping inwards from it along the face using the sliding bevel as your guide. Square these marks across the end, and then repeat them on the other face.

Lastly, set a marking or cutting gauge to the exact thickness of the pin piece, and scribe a line all round the end of the tail piece If you’ve been allowing for extra length, add that to the scribed thickness This will make the tails slightly too long, when the joint is complete, trim them flush with a block plane

At this stage, a very wise precaution is to hatch in or mark with an X all the bits you’re going to cut out

Cutting the tails and pins

The next essential is to have the right saw. An ordinary tenon saw is too heavy, you need the lighter version actually known as a dovetail saw, or the still finer gent’s saw. But even one of these, especially if new, will have too much ‘set’ the teeth will project too far sideways giving too wide and inaccurate a cut. You can remedy this by placing the blade on an oilstone, flat on its side, and very lightly rubbing it along. Do this once or twice for each side.

To make your cuts, cramp the tail piece in a vice (If making, say, two identical sides for a box, you can cut more than one piece at the same time.) Align the timber so that one set of sloping marked lines is vertical Cut along all these, one after the other, before tilting the piece the other way and cutting those on the opposite slope.
Saw immediately on the outside of each marked line, and begin each cut with the saw angled backwards, steadying its blade with your thumbnail Once you’ve got the cut established tilt the saw forwards to make sure you re keeping to the line on the other side Lastly, level the saw up as you finish the cut Whatever you do, don’t cut down past the gauged line.

The next step is to use your gauge to mark the thickness of the tail piece in turn on the pin piece.

A neat trick follows Hold the pin pieceina vice, and cramp the tail piece over its end in exactly the intended position. Then, inserting the saw in the cuts you’ve just made, use it to score corresponding marks on the endgrain of the pin piece. Square these across its faces.

At this point you can remove the waste from between the tails. Begin by sawing out the little piece next to each of the two outer tails; then use a chisel. (Some people like to get the bulk of the waste out with a coping saw first.) Drive the chisel down into the face each time, keeping well in front of the gauge line, then tap the blade into the endgrain to get the chips up and out Turn the piece over and do the same on the other side.

Marking out the tails

1 Plane both pieces to exactly the same width, and check that the ends are dead square. Correct with a block plane if necessary.

2 Square the end pins’ width along the tail piece, then slant a measure between the lines to give handy divisions for the pin centres.

3 Use a gauge to extend these centre marks from the slanting line down to the end of the piece, where the tails will be cut.

4 Make another mark 3mm either side of each centre mark. This will give you the widths of the tails at their widest.

5 Set a sharp marking gauge, or preferably a cutting gauge, to the exact thickness of the pin piece or a bit more – but no less.
6 Score a neat line all round the end of the tail piece with the gauge. It’s usual to leave this visible in the finished joint.

7 Set a sliding bevel (or make a card template) to a slope of 1 in 6 – ie, six units in one direction and one unit in the other direction.

8 Use the bevel or template to mark out the slope of the tails, working inwards from the marks which denote the tail widths.

9 Square the width marks across the end of the piece, then mark the slope again on the far side with the bevel or template.

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