I'm making a spice rack for my brother. The sides are 3/8" sapele and I am planning on attaching the shelves with through mortise and tenons. The mortises are relatively thin (3/8") and wide (1.5"). I cut the mortise for the middle shelf without a problem, but trying to cut the bottom shelf (which is very near the bottom end of the sides) caused tear out (layers of the wood between the mortise and the edge) to peel away.
I will clamp a block down right to the edge of the mortise, which I'm sure will help.
Any other suggestions?