How do I cut a dovetail joint by hand?

Marking from one face, cutting tails first, transferring to the pins with a knife rather than a pencil, and chopping the waste from both sides.

Difficulty: advanced
Time: 1 hr 30 min
Read: 6 min
Safety: caution

Short answer

Mark a baseline all round with a gauge set to the mating board's thickness. Saw the tails, remove the waste, then use the finished tails to knife the pins directly onto the end grain of the other board. Saw on the waste side of every line, chop halfway from each face, and pare to the knife line. Fit dry once, then glue.

A dovetail is a mechanical joint before it is a glued one: the wedge shape means the tails physically cannot pull out of the pins in one direction, which is why drawer fronts have been made this way for three hundred years. Cutting one badly is easy and cutting one well is a matter of two disciplines — sawing consistently to a line, and transferring the first half of the joint to the second half by knife rather than by measurement.

Safety

Dovetailing is done with a very sharp saw and a very sharp chisel, often with the workpiece held vertically in a vice and your hand close to the cut. Chop with the workpiece clamped and both hands behind the edge, never with a hand steadying the far side of the wood. A chisel that is blunt needs more force and slips further when it does slip.

What you'll need

A dovetail or fine tenon saw
Sharp bevel-edge chisels
A marking gauge and a marking knife
A sliding bevel or a dovetail marker
A vice or clamps
A coping saw or fretsaw (optional)

The parts of a dovetail joint, and which way it resists pulling

Step by step

Prepare both boards square and to identical thickness.Dovetails expose every inaccuracy. The ends must be square in both directions and the two boards the same thickness, or the joint cannot come out flush however carefully it is cut.
Set a marking gauge to the thickness of the mating board.Scribe a baseline right round both boards with that one setting. Both halves are then referenced to the same number, and the shoulders will land together.
Mark the tails out on the end grain.A slope of roughly one in six for softwood and one in eight for hardwood — the exact number matters far less than every tail being the same. Mark the waste clearly with a pencil scribble; sawing the wrong side of a line is the classic first mistake.
Saw the tail sides down to the baseline.Keep the saw plate vertical and let the slope come from how the board is tilted in the vice, or tilt the saw and keep the board upright — pick one and stay with it. Saw on the waste side of the knife line, leaving the line just visible.
Remove the waste between the tails.Coping saw close to the baseline then pare down to it, or chop straight down with a chisel. Either way work halfway from one face, turn the board over and finish from the other, so the fibres break out into the middle rather than out of a face.
Clean the baseline back to the knife line.Pare with the chisel bevel up, back flat on the wood, taking thin cuts. A baseline that is undercut very slightly in the middle will still pull up tight and will not stop the joint closing.
Transfer the tails to the pin board.Stand the pin board upright in the vice, lay the tail board on its end grain exactly in position, and knife round every tail. This is the step that decides whether the joint fits. Do not measure the pins — copy them.
Square the knife lines down the face and saw the pins.Saw inside the lines, on the waste side, keeping the cut vertical. Any drift here shows as a gap on the show face.
Chop and pare the pin waste to the baseline.Again halfway from each face. Check the walls are square with a small square, because a pin sloping inwards will stop the joint going home and a pin sloping outwards leaves a visible gap.
Test fit once, with hand pressure only.It should go together most of the way by hand and need light taps for the last part. If it needs a mallet from the start it is too tight — pare the pins, not the tails, because the tails carry the show slope. Repeated dry fits crush the fibres and give you a loose joint.
Glue up, clamping across the joint rather than along it.Use a clamping block notched to press on the tails only. Check the assembly is square by diagonals before the glue grabs.
Plane the joint flush after the glue has cured.Plane inwards from each end so you do not tear the corner off, or sand it back. Any tiny gaps left can be closed by tapping the surrounding fibres over with a punch before finishing.

Tips

A through dovetail shows end grain on both faces and is the joint for boxes and carcasses. A half-blind dovetail stops short so nothing shows on the front, which is why drawer fronts use it — the technique is the same but the pin sockets are chopped rather than sawn right through.
Cut all the tails on all the boards in one session. Consistency comes from repetition, not from concentrating harder on each one.
Number and mark the mating corners as soon as they are cut. Dovetails fit their own partner and nothing else.
Make a practice joint in the same timber as the job, not in scrap pine, because the wood dictates how the chisel behaves.

Common mistakes

Measuring the pins instead of copying them from the cut tails — Every saw cut wanders a fraction. Copying transfers the actual joint you cut rather than the joint you intended, which is why the transfer step exists at all.
Sawing on the line rather than beside it — The saw kerf has width. Cutting on the line removes half the material you needed and produces a joint that is loose before you have touched a chisel.
Dry fitting a tight joint several times — Each assembly crushes and compresses the fibres. By the third fit it slides together sweetly and by glue-up it is loose, with no wood left to take up.

If it doesn't work

Gaps at the tips of the pins on the show face

Cause: Sawed outside the knife line on the pin board, or the pin walls slope outward — Fix: Check squareness of the pin walls with a small square before assembly. On a finished joint, tap the fibres over with a punch or glue in a slim wedge of the same timber, aligned with the grain.

The joint will not close by the last few millimetres

Cause: Waste left in the corners at the baseline, or a bulge in the middle of a socket — Fix: Take it apart, chalk the tails, push together and look for rub marks. Pare exactly where it is rubbing rather than everywhere.

The assembled corner is not square

Cause: The board ends were not square before marking out — Fix: Nothing can be done after glue-up. Shoot the ends square on a shooting board before marking out next time.

Questions people ask

Do I cut tails first or pins first?

Either works and both have good practitioners. Tails first is easier to learn because the tail board can be laid flat on the pin board for transfer, and the sawing is more forgiving. Whichever you choose, the second half is always copied from the first, never measured.

What slope should the dovetails be?

Around one in six in softwood and one in eight in hardwood is traditional, on the reasoning that a steeper slope leaves weaker short grain at the tail tips. Consistency matters far more than the exact ratio.

Can I fill a gap in a dovetail?

A small one, yes — a sliver of the same timber glued in with the grain running the same way is almost invisible after planing. Filler is not, because it takes finish differently and appears the moment you apply oil.