Rout perfect mortises and tenons
Leigh Industry’s Super Frame Mortise and Tenon Guide
Tester: Jody Garrett
The mortise and tenon ranks as the strongest of all joints, but many woodworkers shun it because it’s challenging to cut by
hand or requires time-consuming setups when done on a mortising machine and table saw. Enter the new Leigh Super FMT (Frame Mortise and Tenon) Guide, which calls on your router to get the job done with high precision and in short order.
The Setup
Out of the box the Super FMT’s heavy-gauge steel jig frame and router sub-base come almost ready to go. Assembly consists of cutting and mounting a 5 x 24″ baseboard to the jig frame for clamping to a bench and attaching the sub-base to your router. The instruction manual provides detail for attaching over 45 different routers, but guidance for additional routers can be obtained by contacting Leigh. Actual router mounting may take 30 minutes, but this is a one-time investment. Centering the router on the sub-base is absolutely critical for producing precision joinery, but using the supplied centering mandrel makes this process painless. You simply position the sliding stops tightly against the router base to “lock in” the router and prevent any lateral movement. The sliding stops also locate the router on the sub-base for speedy removal/reattachment without impacting accuracy. The jig uses one bit, one guide, and one setup for each standard joint. Optional bits and guides are available for cutting mortises and tenons from 1/16” wide X 1/8” long to 1/2″ wide x 5″ long.
Trial Run
After setup, I cut perfectly fitting 5/16” x ½” inch mortise-and-tenon joints in minutes, all at one location. I next challenged the system by making eight 3/8” x 1 1/2″ mortises and tenons. Here I determined the secrets for routing perfection. When making mortises, initially mortises overlap the plunge holes, working from one mortise end to the other. Then pull the plunged bit through the holes to create clean, straight mortise walls. To make mortises deeper than ½”, plunge- rout in increments, using your router’s stops. Doing this prevents burning. To shape clean, crisp tenons, again work in increments for long tenons and initially make very shallow “climb” cuts (moving the router clockwise) to establish the shoulders. Always make test cuts and test-fit parts to ensure a flush, snug joint. Unlike other jigs, the Super FMT’s precision adjustments are easy to make and dead-on accurate. By turning the left guide pin 1/8 of a turn for a 0.001″ adjustment you can literally “dial in” the perfect fit.
Tester’s Take
For the quality, versatility, and ease of use, the Super FMT represents a great value. If you’ve shied away from mortise-and-tenon joints, especially those with more than one tenon, or mitered mortise-and-tenon joints, you might rethink your position. For the woodworker who plans for a lot of mortise-and-tenon joints in his or her upcoming projects, this may be the time-saving ticket. For chip collection, consider the Vacuum Box as a must-have accessory.
Super FMT #150724 $399 – Value Alert: This month only, buy a Super FMT and Get a Free 16 Piece Guide Set Direct From Leigh – A $99 Value!
Super FMT Vacuum Box #150725 $49