Laying out a dovetail by eye and by template
A dovetail holds because the tails flare out and the pins lock behind them. The flare is the slope, and almost every layout question comes down to choosing it and sticking to it.
Choosing the slope
The usual rule is 1 in 6 for softwood and 1 in 8 for hardwood. A steeper slope grips better but leaves a thin, fragile corner on the tail. A shallower one is stronger at the edge but looks timid and pulls apart more easily.
Marking out
- Set a marking gauge to the thickness of the mating board and scribe a baseline on both faces and edges.
- Draw a 1 in 6 line with a bevel gauge or a small template cut from offcut ply. A template beats freehand every time you need to repeat a layout.
- Mark the half-pins at the edges first, then space the tails evenly between them. Uneven spacing is fine if it is deliberate.
- Square each line across the end grain and down the opposite face.
Sawing and chopping
Saw on the waste side of the line and stop at the baseline. Chop out half the waste from each face, working toward the middle, so the baseline stays crisp. Then transfer the tails to the pin board with a sharp pencil or a knife.
The common failure is crossing the baseline by a hair. Take a moment before each cut, and leave a little for the chisel.