Instructions

Getting started

Cross cut a 1"-thick x 3 1/2"-wide x 15 1/2"-long piece of maple to get one piece 8 1/2" long, and another one 6 1/2" long. These two pieces eventually become eight separate pieces–forming two frames–but for now, working with them as is improves speed and accuracy. Cut 45º mitres on both ends of each piece, then prepare to mill 1/2"-long dovetail slots across the ends of each mitre. These slots are for splines, and regardless of how you mill them, the angled end of each mitre must remain flat on your router table during the operation. You can build a sled for this job, or use a mitre gauge if your router table includes a mitre slot. Just be sure to clamp a 4"-tall auxiliary fence to your mitre gauge first, then clamp your wood to this fence before sliding the whole thing over the spinning dovetail bit.

Building the frame

Once the mitres and dovetails are cut, it's time to make your two pieces of wood into four. Set your tablesaw fence to 1 5/8" and rip the pieces to width. These four pieces will come together to form a really thick frame but will eventually make two frames, once they’re ripped in half after assembly.

On your tablesaw, cut 1/4" x 1/4" rabbets to accept the glass and backing. Cut rabbets on the rear inside edges of all four pieces.

The butterfly splines look difficult to make, but they're easy if you're careful about measuring and machine set-ups. To make the splines, put two pieces of your frame together so the dovetail slots align, and measure the width between the two top edges. In my case, each dovetail groove was exactly 1/2" long, so my total measurement was 1". Next, measure the width of each dovetail at its widest point to determine the thickness of your butterfly splines.

Rip and plane a few 12"-long pieces of walnut to the exact dimensions of your slots (1/2" x 1" for mine), then move to the router table. Set the height of your router bit so the top edge of the cutters are exactly centred on your blank, and move the fence so about 1/8" of the cutter is exposed. Using featherboards and a pushstick for safety, run the stock over the cutter, flip the stock to cut the other side, then rotate it 180º and repeat the process on the other side, for a total of four passes. Move the fence back another 1/8" (exposing more of the cutters) and do another series of passes, then check the spline for fit in a dovetail slot. Adjust the fence a little at a time, and continue making passes until the spline fits perfectly into a slot. Any fine adjustments can be made with some 150-grit sandpaper wrapped around a wooden block.

Cross cut your double-dovetail blank to make four butterfly splines, each measuring 1" long. Test-fit all splines into the assembled frame and adjust if necessary. Apply glue to the mitre faces and clamp the frame together. If all looks good, brush glue into the dovetail joints and insert the butterfly splines. Once the glue has dried, sand the splines flush with the surface of the frame, then head back to the tablesaw.

With the saw blade raised just a hair lower than the thickness of the sides, set the fence to 3/4" and rip the frame in half by taking four passes, turning the frame for each pass. Complete the separation of the two halves by finishing the cut with a sharp utility knife, then sand away any ridges or saw marks with a random-orbit sander.

Finishing up

To complete the frame, cut your back panels from 1/8"-thick hardboard and have two pieces of glass cut to the same size.

I finished my frames with a coat of boiled linseed oil. Allow the oil to cure for three days, then add an even coat of polyurethane. These two finishing steps complement each other well: linseed oil makes the maple figure stand out and highlights the dark colour of the walnut, and the poly creates a nice sheen and good protection.