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Wedged Mortise & Tenon Gaston SC

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.

Paulownia Barn, LLC
(803) 381-8735
405 Hydrick Road
Swansea, SC

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The Home Depot
(803)781-0877
5200 Fernandina Rd
Columbia, SC
Hours
Mon-Sat: 6:00am-10:00pm
Sun: 8:00am-8:00pm

Lowe's
(803) 808-5460
5570 Platt Springs Road
Lexington, SC
Hours
M-TH 7 am - 9 pm
FRI-SA 7 am - 10 pm
SU 1:30-7 pm

Fastenal- West Columbia
803-356-4334
3914 Platt Springs Road West Columbia, SC, 29170
West Columbia, SC
 
Ace Hardware of Cayce LLC
(803) 391-4223
815 State St, Parkland Plaza / Bi-Lo Shopping Center
Cayce, SC
 
The Home Depot
(803)359-1194
5600 Sun Set Blvd
Lexington, SC
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Mon-Sat: 6:00am-10:00pm
Sun: 1:30pm-8:00pm

LOWE'S OF WEST COLUMBIA, S. C.
803 926-8885
2829 AUGUSTA RD WEST COLUMBIA, SC, 29170
West Columbia, SC
 
Lowe's
(803) 926-8885
2829 Augusta Road
West Columbia, SC
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M-SA 6 am - 10 pm
SU 1:30-8 pm

Three Fountains Ace Hardware
(803) 957-4991
2930 Emanuel Church Rd
West Columbia, SC
 
MANN TOOL & SUPPLY
803-252-7777
802 CHRIS DR. COLUMBIA, SC, 29169
Columbia, SC
 
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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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