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m he sliding dovetail is a mar-Iil velous method of joining a D board across the grain of an-M other in a "T" configuration. Since the parts interlock and don't really need to be glued, the wood is free to move in situations where long grain is joined to cross grain, such as joining drawer frames to carcase sides. When the joint is across the grain of both boards, as when fastening a shelf in a carcase, the interlock of the sliding dovetail compensates for the weakness of an end-grain glue joint.

But sliding dovetails present problems. A slightly g undersized pin can be quite loose in the socket, mak-% ing a very weak joint. A slightly oversized pin, even | one that goes together when dry. may stick before it is | completely assembled with glue, and that's the stuff of

§a woodworker's nightmare. By tapering one side of a sliding dovetail, as shown in Fig. 1, we can get a tight

FIG. 1: TAPERED SLIDING DOVETAILS

Socket narrower at front than at back.

Gap closes as sbeH slides forward. -

\Cut top edge square across board.

Angle bottom edge to make tapered socket.

Pfn fits socket; narrower at front than at back.

A spacer half the width of the router base is a sick, repeatable way to position the T-square. The smaH brad on the centerline of the socket Makes relocation a snap.

FIG. 2: LAYING OUT THE SOCKET

setup for square cut rftmcuBOAM)

setup for tapered cut

A spacer half the width of the router base is a sick, repeatable way to position the T-square. The smaH brad on the centerline of the socket Makes relocation a snap.

joint but avoid sticking, becausc the joint will only be tight when fully assembled. The secret to success is to get the joint to come tightly together just when the two pieces are in the correct position. This article will explain how to get that "just right" fit when cutting a tapered sliding dovetail with a router.

The usual arrangement is to make the top side of the dovetail straight and to taper the bottom side, as shown in Fig. 1. The socket is cut with a hand-held router guided by a shop-made T-square. The T-square is angled slightly to cut the tapered side of the socket, as shown in Fig. 2. The pins are cut on a router table with a jig to hold the boards upright, as shown in Fig. 3. A fine adjustment screw allows the final cut to be made with a succession of passes, each removing a few thousandths-of-an-inch, until the fit is perfect.

Sliding dovetails are usually used in mirror-image pairs, a left side and a right side, and this system will make both right-hand and left-hand dovetails simply by turning over one of the jigs.

Making the Jigs

The T-square guides the router for cutting the sockets, as shown in Fig. 2. I constructed my square from a piece of '/4-in. tempered hardboard and a piece of 5/4-in. high-density particleboard. The long sides of the hardboard must be accurately parallel so that both sides of the square can be used. After sizing the piece on a tablesaw, 1 hand planed the edges and checked for constant width with a dial or vernier caliper. The guiding edge of the particleboard should also be flat. Glue the two pieces together precisely at right angles.

The hardboard spacer shown in Fig. 2 measures exactly half the diameter of the router base. It simplifies positioning the T-square and helps ensure uniformity. Like the T-square, you'll use it often, not just for making sliding tapered dovetails. Make it out of '/.»-in. hardboard, and either mark the width or make it square to avoid using it the wrong way.

The pin jig shown in Fig. 3 holds the board upright

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