CutCalc

Layout

Dovetail layout

Half-pins at the edges, equal tails, equal pins between them. You choose how wide the pins are and the slope, 1:8 or whatever the wood wants. The page marks the end from one edge so you can walk a gauge or a knife down the board.

Units

8 means a 1:8 cheek. 6 is the softer-wood habit.

Tail width

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Shop estimate. Measure your stock and cut a test on scrap.

How to use it

  1. Measure the end the tails will be cut on.
  2. Choose how many tails. One tail is a legal, slightly odd, joint.
  3. Set the half-pin at each edge and the full pin between tails. They do not have to match.
  4. Set the slope as the run of the ratio. 8 means 1:8, a common hardwood slope. 6 is the softer-wood habit.
  5. Mark from the same edge the page used. The drawing is that edge on the left.

The formula

Tail width = (board − 2 × half-pin − (tails − 1) × pin) ÷ tails. Cheek angle = arctan(1 ÷ slope).

  • Half-pin. The pin at each edge. Two of them are subtracted before the tails share what is left.
  • 1:8. The cheek rises 1 unit across 8 units of tail length. The angle is about 7.1° off square.
  • Marks. Distances from the start edge to the end of each pin and each tail.

Worked example

A 6 inch end, three tails, and ⅜ inch pins including the half-pins, gives tails 1.5 inches wide. The marks from the left edge fall at ⅜, then each tail and pin in turn, and the last half-pin ends at 6.

A 1:8 slope leans the cheek 7.13° off square. That is atan(1/8). Softwood often uses 1:6 instead. Change the slope field rather than guessing the angle.

What it will not decide

  • Equal tails and equal full pins. A graduated pin layout is a different drawing.
  • It does not set the baseline depth. That is the thickness of the mating piece, minus a hair if you want the ends proud.
  • The slope is the angle you cut. It says nothing about how the joint will hold.

Questions

What is a half-pin?

The partial pin at each edge of the tail board. Calling it half does not mean it must be half the middle pin. Type the width you want.

Is 1:8 the right slope?

It is a common hardwood slope because the cheek is not so steep that the tail corners chip, and not so flat that the tail is a ramp. Softwood often uses 1:6. The wood and the chisel decide. The page only converts the ratio you type.

Through or half-blind?

The spacing along the end is the same. Half-blind changes how deep the pins are sawn, not where the tails sit across the width.

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