How to cut a tenon on a long board with a router jig
Here's the solution Tom McLaughlin used on his low pencil-post bed.
When building beds, like my cherry low pencil-post version in FWW #296, I often need to cut tenons on the ends of the long rails. While I typically turn to my tablesaw to cut tenons, that’s not an option for me on bed rails, which are often large, and therefore unwieldy and unsafe to tenon on my saw. Decades ago when working with my mentor, P.A. “Pug” Moore, we used a radial arm saw. It was quick and easy. Those saws have become less and less popular, however. Not even my current shop has one. Needing a smart alternative, I paired a stout jig for holding the rail with a guide bushing. This setup gives me an adaptable method for creating different tenons in one shot, routing the cheeks and shoulders at the same time.
The jig itself comprises three parts: the clamping shoe, the tab, and the platform.
The shoe is the biggest part. It has a base for clamping to the bench and two walls that fit the workpiece snugly. Toggle clamps offer extra security.
The tab is a small, removable piece that defines the length and width of the tenon as the bushing (and router bit) travel around it. Because of the bushing, you’ll need to do some math to figure out the tab’s size and location.
The platform sits 90° to the shoe. In the picture, it’s the upside-down U-shaped piece screwed to the shoe. The platform provides a stable base for your router. As such, it needs to be perfectly square to the shoe. If it’s not, the tenon’s shoulder won’t be either.
From there, all that’s left is to rout.