Matt Grisley, president of Leigh Industries, came by the WOOD magazine shop today to demo his company’s newest toy, the Super FMT (frame mortise and tenon jig). This product is a scaled-down, less-expensive version ($450) of the original FMT, launched about six years ago and soon to be called the FMT Pro, which sells for around $900.
The Super FMT works exactly like the original FMT, letting you cut precisely matching mortises and tenons with the same bit in the same router. The body of the jig is made of sheet steel rather than machined aluminum, which cuts the cost dramatically. Here’s a brief summary of how it works.
After mounting your router to the included rectangular subbase, you install a bit and set it to the desired depth of cut. Next, you select one of the template guides. (It comes with five guides for making 5/16″-thick mortises and tenons; you can also buy extra guides in 1/4″, 3/8″, and 1/2″ for a total of 21 guides. You can also use combinations of sizes to get smaller mortises and tenons.) Install the template into the holder on the left. Now insert the centering template in the opening where you’ll do the routing, and align your board’s mortise or tenon layout lines, sliding the top front to back or right to left to get to the desired spot. Then clamp the board in place. The other big difference between this unit and the original is the clamping system. Where the original used integrated cam-action clamps, the Super FMT uses two small F-style clamps that reach through drilled holes in the jig body. A rare-earth magnet on the fixed jaw holds it in place while you slip the adjustable jaw over the bar—pretty nifty.
Once you’ve got the board clamped in place, turn the router on, plunge, and use the subbase’s guide pin to follow the template guide. For tenons, you track around the guide, and for mortises, you track inside the guide. This creates perfectly matching mortises and tenons. Like its big brother, the Super FMT has adjustments for squaring the front of the guide to the top and for tightening the fit of the joint. Matt had shipped us a sample unit and asked me to mount it on a board but not go any further. Then when he arrived he assembled it and had it turning out perfect-fitting joints in less than 30 minutes.
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