I am currently making my first workbench from Chris Simpsons design in 'The essential guide to woodwork' . Though it is stated here that sofwood will suffice for the underframe , I have experienced some cracking in the leg bottoms(red deal) when making the crossrail mortices. I have tried to salvage the legs by using wood glue on the cracks , but have yet to dry assemble the frame. My questions are - the proposed wedged m & tenon joints place the wedges within the tenon and I think that the tenon may split , would it be better to put the wedges between the tenon and mortise wall -top and bottom - rather than within the tenon ? some of the cracks so far happened when I tried to hammer in a tight tenon . How loose/tight should such joints be ? Any info would be great , Cheers .