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Wedged Mortise & Tenon Concord NH

Experiment with the notch's angle. The wider the taper, the stronger the joint. My taper is 3 degrees, but you can increase it up to 8 degrees. 4. Test the bend. My flexible strips are only 1/8 in. thick opposite the strain-relief hole, so they bend easily.

Goosebay Sawmill & Lumber
(603) 798-5135
83 Dover Road Route 4
Chichester, NH

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Steeplegate Mall
(603) 229-0100
270 Loudon Rd
Concord, NH
Store Hours
Sears Stores
Store Type
Sears Stores
Hours
Mon:10-21
Tue:10-21
Wed:10-21
Thu:10-21
Fri:10-21
Sat:8-21
Sun:10-18.5
Store Features
Mon:10-21
Tue:10-21
Wed:10-21
Thu:10-21
Fri:10-21
Sat:8-21
Sun:10-18.5

Lowe's
(603) 310-2520
2 Commerce Drive
Hooksett, NH
Hours
M-SA 7 am - 9 pm
SU 8 am - 7 pm

Lowe's
(603) 729-2016
48 Lowes Drive
Tilton, NH
Hours
M-SA 7 am - 9 pm
SU 8 am - 7 pm

Heritage True Value Hardware
(603) 942-7741
1382 1st New Hampshire Tpke
Northwood, NH
 
Lowe's
(603) 573-4101
90 Fort Eddy Road
Concord, NH
Hours
M-SA 6 am - 9 pm
SU 8 am - 7 pm

Country 3 Corners True Value
(603) 529-7539
833 S Stark Hwy
Weare, NH
 
Bryant&lawrence True Value Hdw.
(603) 286-4322
268 Main St
Tilton, NH
 
Belmont True Value Hardware
(603) 267-8510
131 Main St
Belmont, NH
 
Bryant&Lawrence True Value Hardware.
(800) 642-7392
268 Main St
Tilton, NH

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Wedged Mortise & Tenon

Wedged Mortise & Tenon

The joint will never loosen!

by Tom Caspar

Tap, tap, tap. The wedges go home, the glue squeezes out and a big smile lights up your face. “This joint isn’t coming apart for a hundred years,” you say. “It’s as solid as a rock!”

Making a wedged mortise-and-tenon joint is richly rewarding. Once you understand how it works (see photo, below), you can’t help but admire the joint’s elegant simplicity. It also sends a message. A wedged joint says to one and all, “This was made by a skilled woodworker.” 

How the Joint Works

Here’s a cutaway view of a wedged mortise-and-tenon joint. Driving in the wedges forces the tenon to flare into a fan or dovetail shape. The mortise is tapered to match the angle of each wedge. Like a dovetail, this joint can’t pull apart after the wedges go home.

This tenon has two unusual features: saw kerfs that create flexible strips and holes that disperse the strain that the wedges create. The wedges cause the strips to bend; the holes prevent the bend from splitting the rail.

Where could you use a wedged joint? It’s a candidate for any joint that receives a lot of stress. A table base is a good example (top photo). Pushing or leaning on this table might slowly force a standard joint apart, but wedges keep this joint locked together. 

The wedged mortise-and-tenon joint isn’t difficult to make, but you should have some experience making standard mortise-and-tenon joints before tackling it.

Tools Required

To make this joint, you’ll need a tablesaw, drill press, plunge router, chisel and a bandsaw. If your mortise’s width is 5/8 in. or more, like the mortise I made, you’ll need a 1/2-in.-dia. top-bearing flush-trim bit ($19). If the mortise is more than 3/4 in. deep, you’ll need a bottom-bearing flush-trim bit ($20) (see Source, below). For a mortise less than 5/8 in. wide, you’ll need a straight router bit and a fence or jig for your plunge router.

Rout the Mortise

Before you begin your project, make a prototype joint (see photo, below). 

Designing Your Wedged Joint

Each part of a wedged joint must often be tailored to fit the joint’s size, intended strength and type of wood. Make a prototype following these steps: 

1. Substitute a notch made with a dado set for the mortise (see “How the Joint Works,” page 45). Taper both of the notch’s sides by angling the miter gauge.

2. Make a full-size tenon. Observe how well the flexible strips bend. You may be able to use smaller strain-relief holes or no holes at all.

3. Experiment with the notch’s angle. The wider the taper, the stronger the joint. My taper is 3 degrees, but you can increase it up to 8 degrees. 

4. Test the bend. My flexible strips are only 1/8 in. thick opposite the strain-relief hole, so they bend easily.

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