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Leigh Mortise and Tenon Jig Poulsbo WA

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
(360)779-9924
21750 Market Place NW
Poulsbo, WA
Hours
Mon-Sat: 6:00am-10:00pm
Sun: 7:00am-8:00pm

The Home Depot
(206)361-9600
11616 Aurora Ave N
Seattle, WA
Hours
Mon-Sat: 6:00am-10:00pm
Sun: 7:00am-8:00pm

Compton Lumber & Hardware
(206) 623-5010
3847 1st Ave South PO Box 84972
Seattle, WA

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The Home Depot
(206)762-2126
7345 Delridge Way SW
Seattle, WA
Hours
Mon-Sat: 6:00am-10:00pm
Sun: 7:00am-8:00pm

DCS Industrial Supply
(360) 697-3280
3203 Trotten Rd NE Unit F Poulsbo, WA, 98370
Poulsbo, WA
 
The Home Depot
(360)307-9200
10991 Silverdale Way NW
Silverdale, WA
Hours
Mon-Sat: 6:00am-10:00pm
Sun: 7:00am-8:00pm

Rockler Woodworking and Hardware #2
(206) 634-3222
3823 Stone Way North
Seattle, WA

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The Home Depot
(206)467-9200
2701 Utah Ave South
Seattle, WA
Hours
Mon-Sat: 6:00am-10:00pm
Sun: 7:00am-8:00pm

Coast Do it Best Hardware
(360) 779-2000
19472 7th Avenue N E
Poulsbo, WA
 
James Lumber and Ace Hardware
(360) 779-5571
19801 Viking Ave NW, Across from bright blue NAPA.
Poulsbo, WA
 
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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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