The sides and top of the Craftsman chest are assembled with screws through the shallow mortises that also hold the tenon plugs. To ensure consistent mortise sizes, I used the router jig shown below. The mortises on the chest are the same size but are set in from their respective edges at different distances. The jig is designed to accommodate that with shims that set against the cleat.
The base parts combined with a pair of fillers form an opening for a guide bushing and straight bit. The width of the opening matches the bushing. The bushing should slide smoothly in the slot without moving from side to side. The distance between the fillers determines the overall length of the mortise. The cleat is screwed to the base.
Routing The Top Mortises
The initial configuration of the jig is used to make the mortises on the front edge of the top. To make the mortises on the rear edge of the top, add the first shim next to the cleat with double sided tape. The drawing above shows both of these steps in action.
Routing the Side Mortises
To rout the mortises in the sides of the case you’ll add the second shim to the underside of the jig. Since the distance in from the edge is the same for the side mortises the jig will need no more adjustment (drawing above).
End Grain Tenon Plugs
To wrap things up, make and install the plugs to fit the shallow mortises you just made. Each plug stands slightly proud of the surface and has a slight chamfer around the top edge.
Because these parts are small, I started with an oversize workpiece to make routing the chamfer easier. The drawing below shows the setup. After routing the chamfer on the end of the board, simply cut the plug free at the table saw and then head back to the router table to make another one. A little glue holds them in place.
Chamfer the Plugs. After forming the chamfer on an oversize blank, cut each plug free at the table saw.
