Step 1

The prerequisite for accurate work is the sound preparation of the timber. Each piece should be prepared flat and true with the ends planed dead square. The first step is to mark the shoulder lines with either a cutting gauge or knife and square.

Step 2

The shoulder line should be fractionally bigger (0.5mm) than the thickness of the wood to allow for a little overhang when the joint goes together. Mark out the two ‘half-pins’ at the edges on the first piece of wood. The ‘pins’ are the bits of wood between the tails so there are two half-pins; one each side. The general rule is that they measure half the thickness of timber plus around a mm, so the two dots on the shoulder line are 7mm in from each edge.

Half-pins

Step 3

The two dots which mark the corners of the half pins are now converted into a 1:8 slope at each side, the result of which is that there’s now one large dovetail in the middle of the wood. A black biro has been used here for clarity; a sharp 4H pencil will produce a finer line, however it may be more difficult to see.

Large single dovetail

Step 4

Mark out the single large dovetail at 90° on the end grain.

End grain transfer

Step 5

There should be roughly one dovetail each 25mm or so across the width. There's no hard and fast rule so it’s up to the woodworker to use his or her judgement to decide how many are needed. The wood here is 92mm wide and as a consequence I’m going to have three dovetails. There are a number of ways to do this, but the easiest is to use a pair of dividers. Set them to around 28mm and ‘step out’ across the end grain, starting at the right hand side.

Starting point

Important!

When the marking out is finished, the width of the pins along the shoulder line should be wider than the chisel that will eventually be used to clean them out. Thus if it's intended that a 6mm chisel be used, the base of the pin should measure 7mm. 

Step 6

Make the first step to mark a ‘dot’ on the end grain.

Using the dividers to make the first step

Step 7

Rotate the dividers through 180° moving from right to left to make the second and third dots; the last one should be a few mm past the dovetail line on the left hand side.

Step 8

Turn the first two dots produced into lines across the end grain of the board.

Turn the first two dots into lines

Step 9

Repeat the ‘stepping out’ process twice more, moving from left to right and starting with the divider point on the left hand side line.

Step 10

Turn the last two dots into lines across the end of the board.

Turn dots into lines across the end of the board

Step 11

Complete the marking out of the dovetail joint and shade the waste. A 3mm chisel will be used to clean out the pins so the base measures 5mm along the shoulder line.