Having finally dug ourselves out from under the heaps of cardboard and packing paper, my wife and I are officially moved in to our new place in Denver. So, having some time on my hands (at long last!), I embarked on my first major woodworking project: building a proper workbench. My design is loosely based on the "Joiner's Bench" in Making Workbenches, except that I've decided to use wedged mortise and tenon and bridle joints on the side frames.
This left me with the need to cut mortises through the 4x4 material I chose for the legs. After laying out the joints on both sides of the board I considered how to proceed.
Without a drill press, using the "drill and pare" method would depend on my ability to accurately drill square holes with a 1/2 inch twist bit. Hmm... not good, even with pilot holes.
I tried the "Neander Way," namely chop it out using chisels entirely by hand (thank you Bob Smalser, for your excellent article describing the process in detail). It worked reasonably well, for a first attempt and I am consoled by the fact that most of the boo-boos will be covered by the mating tenon's shoulders. However, cutting deep mortises on a Workmate is pretty time consuming -- and tiring to boot, given how low the Workmate is.
Then I remembered all those fancy router mortising jigs. My eyes wandered over to the EZ Smart box... Okay, so I'm a slow learner! I grabbed a scrap of 2x6, squared it up to one side of the Workmate and clamped the guide rail to it. With the 4x4 clamped in the Workmate's jaws, my plunge router had plenty of xy-direction travel to trace the outline of the mortise. I chucked a 1/2" straight bit (2" long) into the collet and ease the running router into the middle of the mortise. This was necessary since the 2" long bit projected about 1/4" below the router's baseplate, even at maximum height. Now for the clever part -- I used the router guide's xy adjustments to nibble my way to the layout lines, and made a pencil mark directly on the guide and router arm at each extreme. Once the marks are made, the work gets real EZ. Run the bit around the racetrack once, plunger it a bit deeper, repeat. For a stopped mortise using the router's depth limiter would be wise. Since I was going for through cuts I just hogged down two inches, flipped and realigned the jig on the opposite side and finished the cut.
You've got to be very precise in laying out both sides of the mortise -- a good combination square or layout gauge is priceless there, or there will be a small shoulder internally. For my purposes it doesn't matter too much since I can just pare out the shoulder at a slight angle to leave expansion room for the wedged tenon.
Eventually I'll get around to building a proper jig to make aligning the rail to the workpiece easier, but for now it's a reasonably expedient solution. Attached are a couple of pictures.
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Originally Posted by Jon Toebbe
