Understanding the Jigsaw Puzzle
The back and sides of the highboy are simply glued-up panels tenoned into the posts. Each end of each of these wide panels is triple-tenoned into the post, and I always leave a little bit of shrinkage space on the bottom edge of the top tenon and the top edge of the bottom tenon in order to accommodate shrinkage across the grain. Sometimes I assemble the base with glue on only the middle tenon on each end of each part. At other times, I’ll glue all three tenons. It doesn’t seem to make much difference. Even though the highboys I’ve built are all living in homes with forced air heat, none — so far — have developed cracked side or back panels, something quite common in period originals.
The front of the base unit is composed of only five parts, in addition to the legs, but the fabrication of these five parts involves the cutting of quite a bit of complicated joinery, so please take some time to study before cutting your stock.
The rail beneath the top drawer of this section, for example, is double-tenoned on each end. It is cut on its back edge with mortises for two drawer runners and one kicker strip. Plus, its front edge is cut to receive the dovetail at the top of the stiles on either side of the center drawer. And the top rail has a fat dovetail cut on either end which is fit into a dovetail socket chopped into the end grain at the top of each of the two front posts. It’s complicated, but the parts will begin to make sense.
The lower unit should be assembled in three stages. First, glue up the very simple back assembly, taking pains to ensure that the panel is square and that the posts at the top of the back legs lie in the same plane. You can check this by laying the back assembly on a flat surface, like a workbench — and it is essential that you make this check, because a back panel that is not truly flat will impart a twist to the unit of which it will later become a part. Then glue up the front of the lower unit, making the same flatness for the top drawer. Although I accomplished this glue-up working alone, it was a harrowing process, and I recommend that you have help because there are so many parts to glue up and fit simultaneously.
Once you have glued the front and back panels to the end panels and installed the many drawer runners, carefully check the alignment of the lower case before you allow it to dry. First, check to see that the front panel is exactly perpendicular to each of the side panels. You can do this with a framing square or by measuring diagonals. Then check to see that the four feet all touch the floor at the same time. You can make some corrections by racking the uncured frame, but any racking correction you make will necessarily create some slight gaps in joinery.