Tapered Sliding Dovetails Westerly RI
West Kingston, RI
Tapered Sliding Dovetails
Tapered Sliding Dovetails
Two jigs make a complicated joint ever so easy.
by Luke Hartle
The tapered sliding dovetail joint is one of the hallmarks of fine craftsmanship. But making it has made many craftsmen pull out their hair! I’ve made it simple, using a jig with a micro-adjust feature for dialing in a perfect fit.
This exceptionally strong joint was traditionally used to bind solid shelves and dividers to the sides of a carcase. A standard sliding dovetail must overcome a lot of friction to go home, but a tapered sliding dovetail is a cinch to assemble. My bookcase on page 70 makes full use of it, additionally joining the top to the sides. The jigs I built are sized to fit the bookcase, but it’s easy to tailor them to another project.
To reduce setup time, I used two routers to make the joint, but that’s not absolutely necessary. You’ll need a 1/2-in. top-bearing dovetail bit ($34), a 1/2-in. top-bearing flush-trim bit ($29), a 3/8-in. straight bit ($23) and a 5/8-in.-dia. template guide.
Build the Tail Jig
1. Make a taper template for routing the tails. First, draw a rectangle (shown in red in Photo 1) the same size as the end of the board that receives the tail. Next, draw two lines (shown in black) inside the rectangle indicating the amount the dovetail will taper (Fig. A, below). Each side of this taper has a 1/8-in. rise over the joint’s 11-in. length, or run. A 1/8-in. rise works equally well if the joint is a few inches shorter or longer. Rough-cut the template 1/16 in. outside the black lines with your bandsaw.
2. Cut to the black lines on the router table (Photo 2), using a top-bearing straight bit (see Sources, below). Fasten the template to the guide board with screws so the template doesn’t flex.
3. Screw the template to a test board (Photo 3). Align the red lines with the board’s edges. Position the template so it’s exactly centered from side to side, clamp it in place and drive in the screws.
4. Assemble the rest of the jig on the test board so it fits tightly (Photo 4). Clamp the braces (C) in place first; then add the ends (B, Fig. B, below).
5. Add two outriggers (D, Photo 5). Stand the jig on a flat surface to ensure these boards are level with the template.
6. Rout a test dovetail with a bearing-guided router bit (Photo 6; see Sources, below). Lower the bit so it cuts 1/2 in. into the test piece. Unscrew the template and remove the jig.
Build the Socket Jig
7. Build this jig around a second test board (Photo 7). To position the fixed guide board, use the same 1/8-in. taper you used to make the tail jig. Draw an alignment mark (shown in red) on the guide board perpendicular to the test board’s edge. Lay the fixed guide board exactly on the line at one end and offset it by 1/8 in. at the other end. Fasten the guide board to the braces (G). The spacer enables this jig to fit the 12-in. top of the &ldq...