Want to add strength and a touch of elegance to a mitered frame? A spline will do it. Splines are very easy to cut on the table saw, using a simple shop-made jig.
Make the Jig
Make the jig about 12″ tall. The jig is simple to make, but a couple of things are key. The cleats must form a perfect 90-degree angle, relative to each other, and a 45-degree angle relative to the base of the jig. Here’s how to make it happen. Fasten one cleat to the jig at 45 degrees, and rest a framing square against it. Make the outside corner of the framing square even with the bottom of the jig. Position the second cleat against the opposite leg of the square. The cleats end 1-1/8″ above the base of the jig.
The 3″ hole, centered 4″ above the base, provides a spot to poke a clamp through the jig.
The wings on the back of the jig give you something to hold onto when making cuts, and ensure that the face of the jig remains perfectly square to the base.
Setting Up The Cuts
Set the height of the blade. It’s best to use a flat-top grind blade so the bottom of your spline cut is dead flat.
Nest the frame against the 45-degree cleats and clamp it to the jig.
With the jig against the rip fence, position the frame over the saw blade.
Cut and Spline
Cut all four corners of the frame.
Glue the spline material into the cut. It should slip in with just a little pressure. Leave the splines oversized for now.
Wait for the glue to dry, then trim the splines close to the frame using a band saw or handsaw. Plane or sand the splines flush to finish them up.
Angling the table saw blade changes the look of the spline.
Angling the blade and making two cuts makes the spline double cool.