Now use your tenons to lay out the locations of your mortises. See the photo at right for how this works. Clamp a piece of scrap to your drill press to act as a fence and chain-drill the mortises in the legs. Make your mortises about 1/16″ deeper than your tenons are long. This will give you a little space for any excess glue.
Once you’ve got your mortises drilled, use a mortise chisel to square the round corners. Make sure your tenons fit, then dry-fit your base. Label each joint so you can reassemble the bench later.
There’s a bit of a trick to joining the front rails to the legs. Workbenches, you see, are subject to a lot of racking back and forth. A plain old mortise-and-tenon joint just won’t hack it. So we bolt it. First study the diagram at left to see how these joints work. Now here’s the best way to make them.