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Woodworking Math

Dovetail joint

A dovetail joint locks two boards together at a corner with interlocking tails and pins. The tails flare out like a dove’s tail, and the pins between them flare the other way, so once the joint is glued the boards can only come apart in the one direction they went together.

The kinds of dovetail

Rockler sorts dovetails into two main families. In through dovetails the pins and tails run all the way through both boards, so the joint shows on both faces of the corner. In half-blind dovetails, also called single-lap, the front board overlaps the ends of the tails, so the joint can’t be seen from the front: the usual choice for a drawer front. A sliding dovetail is a different joint again: a dovetail-shaped tongue slid into a matching groove, used to fit a shelf or a rail across a panel.

Slope

Dovetails are traditionally cut at 1:6 in softwood and 1:8 in hardwood.

The angle of the tails is written as a ratio, 1:r, meaning the side moves 1 unit across for every r units along. A 1:6 slope is about 9.5° from square and 1:8 is about 7.1°, which is plain trigonometry. Which slope to use is a matter of tradition rather than measurement.

Traditional rule, stated by Fine Woodworking (Taunton Press), Lee Valley Tools and Rockler

How it’s cut

By hand, the tails are sawn first, then traced onto the end of the other board so the pins match them exactly, and the waste is chopped out with a chisel. A router with a dovetail bit and a jig cuts both parts by machine; the jig’s manual says which bit and guide bushing it was designed around, and its spacing may be fixed or adjustable.

Why the joint holds

Rockler puts the dovetail’s durability down to the combination of a large glue area and the mechanical lock of the tails and pins. This site gives no strength numbers for dovetails: the published tests we found each used a different rig, so their results can’t be compared or averaged.

Related joints

Sources

  1. Rockler, Woodworking furniture joinery: butt joints, mortise and tenon, dovetails, read 2026-11-07
  2. Fine Woodworking (Taunton Press), Chris Gochnour, "Laying Out Dovetails", Fine Woodworking #190 (2007), read 2026-11-07
  3. Lee Valley Tools, Veritas Dovetail Markers (1:6 softwood, 1:8 hardwood), product 73357, read 2026-11-07
  4. Rockler, Rockler Dovetail Saddle Squares (1:6 and 1:8), read 2026-11-07

Proportions marked as a traditional rule are shop tradition, not measurements. This site gives no joint-strength numbers: the published tests each used a different rig. How we source these numbers.