If you want to build boxes with splined miters, using a jig like this along with your table saw makes the job easy.The cradle i
s made of two boards attached at 45 degrees to two outer boards. Your box sits in the jig which rides along the table saw fence while the blade cuts a perfect kerf in each corner. Move the fence to make a second kerf in each corner if you like.If you use a flat tooth blade, the bottom of the kerf will be flat and your miter key will fit right in. If you use an ATB (alternate top bevel) blade, you'll have a little clean up to do with a chisel in order to flatten the bottom of the kerf so the key fits snugly.
(I had trouble getting clear shots of the blades and yes, I know they desperately need to be cleaned. : )
