Leigh Super FMT Frame Mortise & Tenon Jig
The Super FMT has made chairmaking easy!
Chairmaking is demanding to say the least. Every joint in a chair is subject to extraordinary stresses and each joint must be crafted with precision. Even the simplest of chair designs, like the one pictured above, require angled and compound angle joints. The Super FMT was designed to meet the rigorous demands of chair construction.
- All tenon workpieces are placed against the sidestop fence. Its unique design allows angles, left or right of the vertical, up to 45º.
- The clamp plate also angles upwards to a maximum of 30º. A compound angle can be created using a combination of sidestop and clamp plate angles.
It's remarkably easy to set up perfectly aligned multiple mortise & tenon joints on the Super FMT. Precision and repeatability are made possible by adjustable table limit stops (circled below) that control the table's range of motion in both X and Y axes. With each mortise or tenon position sighted and limit stops set, you're ready to rout double, quadruple, or even triple joints with the same ease and precision as a single mortise & tenon.
Double and Quadruple Joints
The sequence below shows each step in making double and quadruple joints. In steps 1 and 2, the side-to-side limit stops are set to produce double inline tenons. Steps 2 and 3 set the front-to-back limit stops which are used to produce side-by-side tenons.
Triple joints are set up just like quads. Make a small stop block to fit between the front-to-back limit stop and post (circled), to position the table for routing the third mortise & tenon.
Floating Tenons and Doweling
Traditional mortise & tenon joinery isn't practical on miter joints, though often they need all the strength that tenons provide. The Super FMT makes it easy to mortise both sides of a miter then glue in a shop-made floating tenon for the strongest possible joint. Doweling, though not as strong, is just as easy to set up and is faster overall when you don't have time to prepare floating tenon stock. Note the doweled bracket feet and base frame for the corner of the blanket chest, opposite.
Wider or Narrower Joints
If you don't have the right guide on hand, or if you want to rout a joint that's wider or narrower than the nearest guide size, you can use the table limit stops to change what any given joint guide allows you to do. The 1" and 2" tenons pictured to the right were both routed using the same 1-1/2" guide.
Guide and Bit Selection
Routing Mortise & Tenon Joints
Routing Angled Joints
Routing Multiple Joints