A mitre sled comes into play when you wish to mitre a panel, or plank, where the width dimension of the panel or board is small compared to its length. If you have a board that is to be the side of a mitred box, for example, it may be 18″ long by 6″ wide. In this scenario, you cannot safely use the table saw fence as a reference to cut the mitre because the width of the board does not provide enough reference surface running against the fence to keep the board from skewing during the cut. The mitre sled solves this issue and turns a challenging joint into a simple process.

Start With the Surface

I used 12 mm thick Baltic birch plywood for the panel of the jig and hard maple for the runner and the solid rear fence. Cut the Baltic birch panel such that the grain of the outer veneers run with the longer length of the rectangular jig, to reduce warping of the jig over time. Using the bandsaw, rip off a maple strip to be used as the runner or guide. Mill the strip to 3/4″ wide by 3/8″ thick so that it will make a snug fit in your table saw t-slot. The panel of the jig is 24 inches wide by 17 inches from front to back. The width dimension was selected to hold a reasonably large cabinet panel, whereas the depth dimension was chosen such that the fence of the jig just hung over the table-saw deck, but not so deep as to allow the jig to tip. A small tip: make the runner about one inch longer than the depth of the panel and have it protrude front and back by 1/2″ – this makes it easier to see while lining the jig up with the t-slot.

Drill and countersink three holes in the maple sled runner. Drill the holes using a 5/32″ bit, which keeps the screws tight in the bore of the drilled hole, eliminating slop. Flip the panel upside down, align the runner with a framing square, and then attach the runner using three 8 x 1″ flat head screws. The runner should be placed so the jig’s surface overlaps the blade, ensuring the jig will be cut by the blade (tilted at 45 degrees) on the first pass. Do not use a pilot hole through the plywood; simply power the screws through using a manual screwdriver. Remove the screws, which poke through the panel slightly, and then grind them back about 1/8″, removing the point from each, thus keeping the screw from protruding through the panel, while achieving maximum purchase with the threads.

A Smooth Fit

Try sliding the jig on the table saw – it will likely bind slightly. Pass the jig back and forth to create burnishing marks on the runner. Remove the jig and then fare the runner using your shoulder plane to establish a snug, yet smoothing running jig.

Raise the blade on your table saw, and verify that the angle is precisely 45 degrees. Run the jig through the table saw, cutting a mitre on the left edge of your jig.

Prepare a solid maple fence that is 27 inches long x 3″ high x 2″ thick. Drill and countersink four 5/32″ holes in the bottom of the panel to mount the fence, offset one inch from the rear edge of the panel. Use your framing square to set the fence at exactly 90 degrees to the mitred edge of your panel, and then clamp the fence in place. Drill a 1/8″ pilot hole through the panel and into the bottom of the fence for all four holes. Fasten the fence, keeping the right edge flush to the panel edge, using four 8 x 1-1/2″ Robertson screws. Do not glue the fence, as you may wish to tweak its position at some later date should the wood move or the jig get dropped. Now that your jig is assembled, ease the edges of the fence with your block plane, followed by a light sanding.

Using the jig

Now for the fun part. Place a stop block in position, and secure it with two f-clamps, to ensure the block does not move. Keeping the stop-block tight ensures that the panel does not creep laterally during the cut. Check the angle of your mitre with your combination square, and make any adjustments to the fence.