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The Woodwright's Guide: Working Wood with Wedge & Edge By Roy Underhill
Secret Miter Dovetail
Before you close the joint, secret miter dovetails look like cliff dwellings built on the slopes of the miters. However, when you bring the pieces together and bunt them with your hand, they close with a clack and the cliff dwellings vanish. There’s no sign of any joint, no trace of the work inside — just the thin line of the miter.
The work begins with the pins. The form of secret miter dovetails dictates that you cut the pins first and then transfer their dimensions to the tail board.
Gauge the inner faces of both pieces to the thickness of
edges and the inside faces.
Saw out the rabbet on the waste sides of these lines. True it with a low-angle shoulder plane, taking care not to go over the miter lines cut on the edges. The shoulder plane is an expensive rabbet plane for end grain. It gets its name from lying flat on the cheek of a tenon and planing the end grain of the shoulder.
Lay out the pins on the end grain of one piece. You can’t use the sliding bevel or an ordinary dovetail template to lay out the angles of the pins on the end grain — the shoulder gets in the way. You can snip a guide out of tin, but if you’re ready to cut secret miter dovetails, you’re also probably able to cut a good dovetail angle by eye.
As with the half-blind dovetails on drawers, you can start the pins by sawing some of their cheeks on the diagonal. Remove the waste with the chisel.
Shear the small shoulders at either end of the joint to the miter, but leave the long square lip until after you have transferred the pin spaces to the mating piece.
Set the end grain of the pin board on the tail board, using the lip and the scribed line as guides. Reach in between the pins and scribe with a knife to delineate the tails. Saw the diagonals and chisel out the waste.
Check the fit of the joint. It will come four-fifths closed before the lips interfere with one another. Now to make them kiss. Take it slowly. The shoulder plane cuts finer, but you can see better with the paring chisel. Besides, shearing diagonal grain in hard wood is a rare pleasure. Push the chisel along, bevel up, shearing off the long corner and ends of the square lip until you have only a gentle rise in the middle to flatten with a few strokes of the plane.
Working carefully, you can make the joint close to a perfect miter leaving no trace of the workmanship inside.
And that’s the problem.
With the workmanship hidden, the secret miter dovetail joint was the hidden place where piecework cabinetmakers could cut corners — badly. These sweatshops have moved on to other parts of the world, but they are still part of the legacy of the old tools and antique furniture that we so admire. When you see an old piece of furniture disassembled for repair, these hidden joints speak the truth.
"The Woodwright's Guide: Working Wood with Wedge & Edge" By Roy Underhill
© 2012 The University of North Carolina Press