Designing Dovetails for Strength and Style
Are higher angles necessary when cutting dovetails in softwoods, and does the dovetail angle affect the strength of the joint? Christian Becksvoort has an answer.
Q:
Do I really need to use higher angles when I’m cutting dovetails in softwoods like pine? Does the dovetail angle affect the strength of the joint?
Bill Fontana, Worcester, MA
A:
No. Although softwoods are more compressible than hardwoods, you needn’t change the dovetail angle to add strength to the joint. Any angle between 7° and 15° will work, regardless of the wood. But stay within that range. If you go below 7°, you’ll start to lose the mechanical strength of the dovetail. Go above 15°, and you’ll leave too much short grain at the tips of the tails, which weakens the joinery.
Thin stock is perhaps the one exception. If you’re dovetailing stock less than 1⁄4-in. thick, go with at least a 10° angle. It increases the glue surface and strengthens the joint—but only slightly.
The art of dovetailing is to aim somewhere between those extremes. The ultimate goal is a strong joint that looks handmade.
At one extreme are skinny, widely spaced dovetails. They look hand-cut, but the joint is weak because most of the material has been removed from the pin board while nearly none has been removed from the tail board. The other extreme is removing roughly equal amounts from the pin and tail boards. Doing so produces a mechanically strong joint, but one that looks machine-cut, and to my eye, unappealing.When it comes to making a strong dovetail joint, the spacing and size of the dovetails is far more important than the angle. The trick is to balance that strength with aesthetics, which means finding the sweet spot between two extremes.
Drawings: Kelly J. Dunton
Fine Woodworking Recommended Products
Leigh Super 18 Jig
Olfa Knife
Marking knife: Hock Double-Bevel Violin Knife, 3/4 in.
Comments
I like variable width tails, then you can use a few thin pins but also have enough "fat" ones to retain strength. That only works if your piece is wide enough of course. I'm thinking 4" drawers today :)
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