Block-guided splined miters
Mitered corners in box projects look great. But because the end grain makes for a weak glue joint, you need to add a spline. Here’s how I use an L-shaped fence to cut the miter and the spline slots.
First, make an auxiliary fence, as shown above, and clamp it to your tablesaw’s rip fence. Now lay out the lengths of the sides, and attach guide blocks to the outside face with double-stick tape or a spot of glue. (Mitering the edges of the guide blocks, as shown at right, creates a ledge for the clamps to cinch the corner together.)
Next, set the blade to 45°, and align the outer edge of the fence with the outside edge of the blade. With the blocks riding against the fence, cut the miters.
After mitering, move the L-shaped fence to the opposite side of the blade. Set the blade height so that it’s half the thickness of the stock, and adjust the fence so that the kerf is 1⁄8” from the inside edge of the miter. Now run the guide blocks along the edge of the fence.
For maximum joint strength, cut the splines so that the grain runs perpendicular to the mitered ends. Assemble the joint with glue and clamps, as shown.
