I'm building a chevalet. The main support post is attached to the base using a double tenon and through mortises. The tenons were cut entirely by hand. I used a 5/8" Forstner bit in the drill press to clear out most of the mortise, then a corner and paring chisels to square and smooth the holes. Since the tenons will be wedged I wanted them to be square rather than rounded.
Given the size of these I'm not sure the typical mortising machine would have the capacity. These are beefy tenons in 3-1/2" thick stock. Regardless, this is the kind of work I really enjoy doing by hand -- very satisfying when you make it fit.