Slabs installed on the base
The joinery here is pretty simple, a couple of tenons and some big lag screws. Because the top is split into two slabs and has a gap between them to hold the tool trays there is a need to really make sure that the slabs won’t move once they are attached to the base. If the slabs move at all it will throw off the vises and make the gap inconsistent, which will either cause the tool trays to get pinched and stuck, or fall through the gap.
In order to lay out the joinery, I opted to cut the tenons first and then figure out how to locate the mortises and cut them second. I made the tenons roughly 1.5″ long and 1″ square, centered on the tops of each leg. The tenons could have been larger, but as always, larger tenons means larger mortises. The tenons are not a problem since they are being cut out of pine and can pretty much all be done with a good saw and a little touch up with a shoulder plane. Mortises are a completely different story.
To locate the mortises I tried balancing the slabs on the tenons, but found this to be too precarious and still required a lot of checking and rechecking. I ended up setting up a marking gauge off the front of the legs to the tenons and marking ‘roughly’ where the mortise would start. I did the same for the back. Now I needed to find where the mortises go laterally.
For the front slab, I used the fact that the tail vise was going to butt up against the right leg, giving me a reference edge to work from. The left leg was measured against the right leg and once the mortises were cut, everything was pretty close. The back slab was a bit harder as I didn’t have an obvious reference edge to work from, but I had the luxury of a little extra length to allow me some wiggle room to trim it down to the right size, so I used the front slab’s length as a guide.
One minor problem I ran into was that the mortises ended up a tad bigger, leaving some slop in the joint. This is not at all good when a vise is going to be pushing against it. This was easily remedied by gluing in some shims on the tenons until everything lined up perfectly and no longer moved.
The final piece of the puzzle was the secure the slabs onto the base. To do this I bored holes a few inches back from the tenons through the top rails and plunged a rather long lag screw about an inch or two into the slabs. Once this was done the whole system was incredibly solid and better yet, incredibly heavy.