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Leigh Mortise and Tenon Jig Mansfield TX

After giving the FMT a thorough workout on a couple of practice chairs my enthusiasm has returned. It takes a few hours and some patience to master the numerous adjustments, but once you do, the jig becomes a real pleasure to use.

The Home Depot
(817)453-4038
1725 N US Hwy 287
Mansfield, TX
Hours
Mon-Sat: 6:00am-10:00pm
Sun: 8:00am-8:00pm

Rockler Woodworking and Hardware #27
(817) 417-0070
4624 South Cooper St.
Arlington, TX

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The Home Depot
(817)447-6602
300 NW John Jones
Burleson, TX
Hours
Mon-Sat: 6:00am-10:00pm
Sun: 8:00am-8:00pm

The Home Depot
(817)293-0343
7950 I-35 W South Fwy
Fort Worth, TX
Hours
Mon-Sat: 6:00am-10:00pm
Sun: 8:00am-8:00pm

The Home Depot
(817)496-3212
1151 Bridgewood Dr
Fort Worth, TX
Hours
Mon-Sat: 6:00am-10:00pm
Sun: 8:00am-8:00pm

The Home Depot
(817)468-4224
4611 S Cooper St
Arlington, TX
Hours
Mon-Sat: 6:00am-10:00pm
Sun: 8:00am-8:00pm

The Home Depot
(972)602-9385
5280 South Hwy 360
Grand Prairie, TX
Hours
Mon-Sat: 6:00am-10:00pm
Sun: 8:00am-8:00pm

The Home Depot
(972)299-9390
373 E Fm 1382
Cedar Hill, TX
Hours
Mon-Sat: 6:00am-10:00pm
Sun: 8:00am-8:00pm

The Home Depot
(817)459-4300
201 Rd To Six Flags West
Arlington, TX
Hours
Mon-Sat: 6:00am-10:00pm
Sun: 8:00am-8:00pm

Brazos Forest Products - Grand Prairie
(972) 602-1225
2760 N Great SW Parkway
Grand Prairie, TX

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Leigh Mortise and Tenon Jig

Leigh Mortise and Tenon Jig

Spot-on accuracy and utmost flexibility--for a price. 

by Randy Johnson

The Leigh Frame Mortise and Tenon Jig (FMT) makes perfect straight and angled mortise and tenon joints in a huge variety of sizes. 

I was excited to give this tool a try. I’ve been dreaming for years about building a set of dining room chairs, but the thought of making all those mortises and tenons always dampened my enthusiasm. 

After giving the FMT a thorough workout on a couple of practice chairs my enthusiasm has returned. It takes a few hours and some patience to master the numerous adjustments, but once you do, the jig becomes a real pleasure to use. 

The FMT base unit retails for around $700 (see Sources, page 83). That’s a lot of cash, but we found the quality and performance of the jig are truly exceptional. It’s a tool that small professional shops or those who want a dedicated mortise and tenon machine will find well worth the investment. 

The FMT base package includes the main jig, a router sub-base, five joint guides, a 5/16-in. spiral router bit and a thick, well-written owner’s manual (Photo 1). The sub-base comes with mounting hardware and can be attached to any currently available plunge router. 

This basic setup enables you to cut 5/16-in.-thick tenons that are 1/2-in. to 1-1/2-in. wide, plus the corresponding mortises. Additional joint guides and router bits are available as options. With them you can make 17 additional standard-size joints as large as 1/2-in. thick by 2-1/2-in. wide and as small as 1/4-in. thick by 5/16-in. wide. By combining different router bits and guide templates you can make joints as small as 1/16 in. by 1/8 in. Now that’s a tiny joint! With all the options, the price of the FMT is over $900.

How it Works

The basic principle behind the jig is that the router sub-base has two guide pins that follow corresponding guides in the top of the main jig (Photo 1 and Fig. A).

The joint guide is interchangeable and  width and length of the joint. The tracking guide is fixed. Its function is simply to direct the right side of the router side to side. The guide pins are tapered and can be adjusted up and down, which makes them ride tighter or looser against the joint and tracking guides. You control the fit of the joint by adjusting the pins. Turning the pins one-eighth turn will change the joint fit by .001 in. Getting good-fitting joints is a cinch considering that a mortise and tenon joint should have about .005 in. of clearance for glue. 

The FMT produces only round-ended mortises and tenons (Photo 2). If you want a square joint you’ll have to trim the parts by hand or with another power tool. This machine also makes angle tenons, thanks to a pivoting front plate (Photo 3). This feature came in really handy when I cut the angled joinery on my dining room chairs.

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