Roy Underhill’s Dovetails

Even though I am 100-percent confident in my ability to join two boards together using the tail-of-the-bird joint, I am always riveted when I get to see how other accomplished woodworkers go about the task.

In fact, when I watch others work, I never fail to pick up some important details.

On Saturday at our Woodworking in America conference I got to watch Roy Underhill from “The Woodwright’s Shop” television show cut some dovetails and discuss his approach, which is planted in history and practical experience. So here it goes.

Underhill began by asking the audience to tell him the rules of cutting dovetails, and he got a big long list of everything from the degree of the slope to the layout to the order of operations. Then he showed us a pre-Civil War tool chest , a beautiful dovetailed tool chest , that violated almost all of those rules. And that’s where he began discussing his approach to through-dovetails.

Layout
Underhill likes to cut the tails first when he can, and he strikes his baselines with a cutting gauge set to the thickness of the work plus 1/32nd.

Then he lays out the tails by first marking the half pins at the edges of the tail board. How wide should the base of each half pin be? One-half your stock thickness. Underhill was joining 3/4″-thick material, so the half pins were 3/8″. He laid those out with a 3/8″-wide chisel. This measurement , 3/8″ in this case , is also the space between the each tail at the baseline.

How wide are the tails themselves? Underhill uses twice the thickness of the material , or 1-1/2″ wide in this case. Then he lays out the tails using a ruler that he lays diagonally on the board. He marks out the centerlines where the holes for the pins should go, then strikes out the 3/8″ dimension by eyeballing the 3/8″ chisel on the centerline. Then pounding it with his hand.

Slope Angle
Underhill isn’t much of a believer in using certain slope angles. He goes by eye and scribes them with a sharp pencil and a bevel gauge.

“Oh, that looks good,” he said. Then he shows the layout to the audience and said that if it looked right it was right.

“Throw away your dovetail marker,” he said. “Just do it. Throw it away.” Then he cuts the tails but does not remove the waste between them.

Transfer the Marks. No Knife
To transfer the shape of the tails onto the pin board, Underhill uses his dovetail saw. He places his tail board on top of his pin board (which is clamped in a vise). And then places the dovetail saw in the kerf and scores the end grain of the pin board. It’s a light mark. Too deep and your saw will jump into the kerf when you are sawing out the pins. You actually want to saw in the waste next to this line.

Then he draws the shape of his pins on the pin board and cuts them with a dovetail saw. To remove the waste between the pins, Underhill uses a coping saw, which he lubricates with mutton tallow.

Chiseling Out
When he chisels out the remaining waste he intentionally leaves a hump in the floors between the pins. Then the clamps the board upright in a face vise to pare out the remaining hump.

To remove the waste left between the tails, Underhill uses two chisels. He used a 3/8″ chisel at the baseline and a 1/4″ above the baseline. He beavered out a “V” using the two chisels (I’ve never seen this technique before).

Then he asked the audience to please not ask him about gluing dovetails.

“I’m a TV woodworker,” he said. “So I can’t glue anything together on camera because we might have to knock it apart and do it again.”

The message from Underhill (or St. Roy to you and me) is this: Dovetails were made in a wide variety of ways by skilled craftsmen. If you are building an original design, make dovetails that look good to your eye. If you are going to copy a piece, use their layout.

“We had a saying at Colonial Williamsburg,” Underhill said. “It was: ‘Stop trying to improve the 18th century.'”

And if the above rational discussion doesn’t settle the arguments about dovetails, I recommend you do what Underhill did later that evening: Arm wrestle the managing editor who prefers pins-first instead of tails-first.

– Christopher Schwarz