Project: Decorative Wedged Tenon Bench

Project: Decorative Wedged Tenon Bench

This sturdy bench is the fourth project I’ve built with wedged tenon joinery in the past year. This time, I primarily used power tools rather than hand tools. But no one can tell, even upon close examination, whether the joinery is cut by hand or by machine. The results have turned out that good!

Despite the great appearance, however, the wedged tenon joints you see in this bench are not your classic wedged mortise and tenons. They are, in fact, decorative loose tenon joints. You can make them with relative ease using just a plunge router and a shop-made jig. Let me show you how.

All-in-One Mortising Jig

Neatly executed, these decorative wedges add contrast to the exposed tenon joinery and enhance the visual impact of the bench.

First, a bit about loose tenon jigs. Regardless of their design differences in terms of complexity and versatility, shop-made jigs for loose tenons work on the same principle: The jig guides the bit to cut mortises of the desired length and width, while the router’s plunge mechanism controls the mortises’ depth. I am a fan of simple jigs, as simplicity means ease of use and less time spent jig making. For this project, I designed a simple router jig that handled all the through and blind or stopped mortises. To be used with a guide bushing, the jig is composed of a slotted base and a hardwood fence. The fence registers against either a reference edge (the end of the top or the front edge of the leg) to cut through mortises, or against a face (the face of the leg or of the stretcher) to cut blind mortises.

Choosing Bit, Guide Bushing

An up-cut spiral bit leaves a rough top edge, but it allows for better chip ejection than a down-cut spiral bit.

The width of a mortise is typically one-third (or less) of the thickness of the mortised stock. Since the stock for the bench is 7/8″ thick, I used a 5/16″-diameter bit. I chose an up-cut spiral bit because it allows faster feed rates (it evacuates chips up and out of the cut) and seems to wander less than other options.

To help clear out the chips, you will want to use a collar that offers a large offset for the bit. If the guide collar is too long for the thickness of the jig, trim the collar shorter with a hacksaw.

Building the Jig

You can create dual-mortise slots from one long slot by gluing a plug into it.

Start with a 1/4″-thick piece of hardboard or MDF as the base. It should be large enough to fully support your plunge router’s base and allow for clamping the jig to the workpiece.

Be sure to factor in the offset of the mortises when attaching the jig’s fence to the base.

Lay out all the mortise slots on the base as illustrated, and then cut the slots.

Method 1: Affix two strips to the jig base with tape. Space them apart with the guide collar you’ll use for mortising.

You can mill these slots on the router table with a flush-trim or straight bit in two ways. In “Method 1,” above, I affix two strips to the jig base to act like fences for guiding the slot cut.

Method 1: The flush-trim bit’s bearing follows the edges of the strips to mill the mortise slot.

Set the distance between them the same as the outside diameter of the guide collar you’ll use to cut the bench mortises. Drill an entry hole through the base, and use a piloted flush-trim bit to rout between the strips (the bit’s bearing follows the strips).

Method 2: The author placed the right side of the jig base on the router table and lowered it slowly onto a spinning bit.

Another way to cut slots is to use your router table’s fence and a straight bit (“Method 2”). If you don’t have a bit the same size as the outside diameter of the guide collar you’ll use for mortising, choose a smaller bit and rout the slot in multiple passes, adjusting the fence after each pass to widen the slot.

Method 2: Be sure the jig’s slots fit the guide collar snugly to create accurate mortises.

Either way, dual-mortise slots can be cut individually or as one long slot, then plugged up in the middle to form two slots.

Preparing the Stock

If you mark out all the mortises on the bench parts using the jig’s base as a template, it can help prevent unnecessary mortising blunders.

Follow the Material List to prepare all the stock to its final dimension — except for the stretcher, which is cut slightly over-length. If you mill your parts from roughsawn stock as I did, it’s a good idea to leave them in the shop for a week or so to acclimatize properly. Another part of preparation is marking your stock. I have found that proper markings reduce many unnecessary errors. After labeling the workpieces with cabinetmaker’s triangles, I used the jig template to mark out all the mortises.

Routing the Mortises

The author finds this a foolproof technique for routing through mortises: sit down and make shallow passes (from left to right), extracting the chips after each pass.

As you build the bench, you’ll use the mortising jig right away to rout most of the mortises. (If you use my jig, it will automatically locate the mortises for you.) To use the mortising jig, clamp it in place on the workpiece, registering the fence against the workpiece’s reference edge or face. For instance, to cut the four mortises in the bench top, use the jig’s two outer slots (right-most slots in diagram). First, center the slots on the top’s surface and butt the fence against one end. Clamp the setup securely and rout the through mortises in multiple passes, as I’m doing in the top photo at right. Remember to keep the router oriented the same way throughout for a consistent path of cut.

To use the jig, align the layout marks on the bench parts with the jig slots. Then, rout each mortise in a series of deepening passes.

To cut the through mortises on the face of the leg, use the jig’s single slot (top slot in diagram). Align the jig’s top edge with the leg’s top edge so its fence butts against the leg’s edge.

One of the jig’s dual mortises closest to the fence can be used to rout a single mortise into each end of the stretcher. Set and clamp the jig carefully, and choose the correct slot when routing!

To rout blind mortises into the top ends of the legs, use the jig’s dual slots that are closest to its fence. Center the template on the stock and register the fence against the leg’s outside face. You will cut the blind mortises on the stretcher later, after trimming to its final length.

Squaring the Mortise Ends

Scribe the mortise ends dead square; it will guarantee a square look after paring.

You certainly can leave the routed mortises round on their ends and cut round-ended tenons to match them.

Pare or chop with a sharp chisel, working from both sides of the cut if it is a through mortise.

However, I prefer the hand-cut look of square mortises here. It is also much easier to cut square tenons.

Check the bottoms of the stopped mortises on the legs and stretcher for any high spots you may have missed when cleaning out the waste.

To square up the mortises, first scribe lines to lay out the square ends. Then chisel down on the scribed lines, checking to be sure the ends are flat and square.

Milling the Loose Tenons

With the right accessories, you can resaw loose tenon blanks safely on the table saw. The author used a Micro Jig GRR-Ripper Push Block GR-200.

For strong joints, size the loose tenons to slip into the mortises without binding or wiggling. I milled the tenons to thickness and then to width, and I trimmed them 1/16″ short to allow for glue to escape — doing all this on the table saw with the help of some accessories, as seen in these photos.

Label the matching tenons and mortises to keep them clear. Chamfer all around the tenon’s bottom end to ease its entry into the mortise.

Then, with the top dry-fitted to the legs, mark the stretcher’s final length.

With the top dry-assembled square to the legs, mark out the final length of the stretcher.

Trim the stretcher to length and rout a blind mortise on each end using one of the two slots on the jig that you used previously to cut blind mortises on legs’ top ends.

Forming Faux Wedged Tenons

When cutting small pieces with a stop block, cut them just shy of their thickness, and break them off with a chisel or knife.

To create the decorative effect that implies wedged tenons, I cut grooves on the ends of the tenons and then inlaid a hardwood strip of contrasting color — I chose maple.

The author clamped the tenons against a spacer block to make a larger registration surface for cutting a groove along their ends. A rotary tool, plunge base and a 1/8 “-dia. bit milled the groove.

For the top’s mortises, I cut a groove along the end grain of the loose tenons. Alternately, for the mortises on the legs, I cut two short kerfs across the tenon thicknesses.

The author offers some sage advice from Tage Frid: apply glue to the groove, not the strip, because the strip expands when it absorbs moisture.

You’ll get the best control by using a rotary tool or small trim router to cut these grooves.

Cut the “wedge” strips slightly longer than the groove depths, then plane them flush after they are glued in place.

Carefully cut the inlay strips to fit into the grooves or kerfs, using safe table saw techniques for cutting thin or small pieces. Lastly, glue the inlay strips to the tenons, then plane or sand them flush.

Wrapping up with Feet, Finish

Photo 1: When bandsawing cutouts that create the bench feet, our author saws between double layout lines to get a more accurate cut.

To create the shape you want for the bench’s “feet,” lay out the desired profiles on the workpieces. I draw two parallel cut lines about 1/16″ apart, then bandsaw between these lines (see photo 1).

Photo 2: Break the edges of the parts with a hand plane or by sanding. Here, the author uses a cornering fixture on the sole of his plane.

Sand to the remaining cutline to smooth these bottom contours. Finally, ease the edges of the parts with roundovers or chamfers, as you prefer.

Photo 3: A large binder clip makes a great handle for a folded cloth used as a finish applicator. The cloth prevents bristle marks and lays finish down evenly.

All that’s left is to finish-sand, glue up the assembly and then apply the finish of your choice. I typically choose to apply finish before the final glue-up, as I did here, sanding with 220-grit abrasive between coats.

Photo 4: After gluing up the legs to the stretcher, complete the rest of the assembly with the bench turned upside down.

After the finish cured on my bench parts, I assembled the stretcher and legs with loose tenons, then glued this subassembly to the bench top with its loose tenons.

Decorative loose tenon joints are easy, strong and versatile, and they add a distinctive touch of fine craftsmanship to this build. Give this technique a try, and I’ll bet you’ll find many other applications for its use.

Hard to Find Hardware

5/16″ D x 1″ H x 1/2″ Shank Freud #75-104 Carbide Up-Spiral Bit (1) #33326
1/2″ Dovetail Guide Bushing, 7/16″ O.D. x 11/32″ I.D. x 5/32″ L (1) #63065

Click Here to Download the Materials List and Drawings.

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