Open Floating Tenon Joinery - gerald@eberhardt.bz

MASTER TECHNIQUES 

Open Floating 

Tenon Joinery 

Mortise and tenon joinery made easy. 

All it takes is a single router table setup. 

Round over one 

edge and end of 

tenon for a snug fit 

When I’m building large frame and panel assemblies 

or doors, I turn to traditional mortise and 

tenon joinery for long-lasting strength. But for 

smaller work, I like to use a modified mortise and 

tenon joint. This floating-tenon provides a lot of 

strength and is quick to make at the router table. 

Floating 

tenon 

Mortise 

depth equals 

bit height 

1 

In a traditional mortise and tenon joint, you need 

one setup for the mortises and another for the tenons 

— which can be time-consuming. To streamline the 

process, I rout an identical mortise in each mating 

piece and join the parts with a “floating” tenon. This 

means you only have one setup for the mortises. 

Chamfer 

stop block 

for dust 

relief 

Workpiece 

Mortises in 

rails and stiles 

are identical 

Stile 

Stop 

block 

Set bit to maximum 

cutting height 

Notch spacers to 

wrap around bit 

Rail 

Length of 

mortise 

matches 

depth 

NOTE: Cut 

grooves for 

panel after 

making 

mortises 

Remove spacers 

to increase 

cutting depth 

a. b. 

Final pass made 

with no spacers 

Spacers make 

routing in several 

passes a snap 

www.ShopNotes.com Page 2 of 3 ©August Home Publishing Company

ROUTING MORTISES 

With an idea of how the joint works, you’re ready to 

get set up and start routing. All you need is a regular 

1 ⁄ 4"-dia. straight bit (for 3 ⁄ 4"-thick stock). 

SETTING UP. Figure 1 shows a good overview of the 

router table setup. But details are left to point out. 

First, the bit needs to be centered on the workpiece. 

This way, the mating pieces will be flush. 

Take a look at the box below to see how I did this. 

Next, you can set the bit height. For the largest (and 

strongest) joint, set the bit to its full cutting length. 

SPACERS. But making a full-depth cut like this puts 

a lot of stress on the bit and router motor. So I limit 

each cut to 1 ⁄ 4" deep and make multiple passes. 

The problem here is having to reach under the 

table to adjust the height of the router. This is timeconsuming 

and can lead to a “stepped” mortise 

where the sides aren’t even. Instead, I rely on a set 

of 1 ⁄ 4" hardboard spacers. You increase the depth of 

cut simply by removing a spacer (Figure 1a). 

STOP BLOCK. Next, clamp a stop block to the router 

table fence. This way you’ll get identical mortises 

in every part. To get the strongest joint, set the stop 

block to rout a mortise that matches the bit height. 

START ROUTING. Now you can turn on the router and 

start making mortises. All the parts are routed the 

same way, so you can do this assembly-line style. 

FLOATING TENONS 

With all the mortises routed, you can move on to 

the floating tenons. Using contrasting wood will 

“show-off” the tenon (like in the main photo). 

SIZING TENON STOCK. To make it easier to work on the 

tenons, I do most of the shaping on an oversize 

blank. It’s sized for a slip fit in the mortises to make 

Centering the Router Bit 

Your goal in making a frame and panel assembly 

is to have the mating parts fit flush. In order to do 

that, the router bit needs to be accurately centered 

on the workpiece. Here’s an easy, no-measure way. 

Start by “eyeballing” the bit as close to the 

center of a short test piece as possible and a hair 

toward the outside edge, like you see in Figure 1. 

Now, make a pass, flip the workpiece end for end, 

and make a second pass (Figure 2). This creates a 

groove that’s slightly wider than the bit. 

To center the bit, gently nudge the fence closer 

to the bit and make a set of passes on a new test 

piece. It may take a few tries. You’ll know the 

router bit is dead center when it doesn’t remove 

any additional material on the second pass. 

2 3 

Backer 

prevents 

chipout 

!/8" 

roundover 

bit 

Fence 

SECOND: Round 

over one end 

Floating tenon 

blank 

FIRST: Round 

over one long 

edge of blank 

Flip workpiece 

over for 

second pass 

FIRST: Adjust fence 

so bit is just off center 

to workpiece 

a. 

NOTE: Bit 

should be 

a “hair” to 

outside to 

prevent 

backrouting 

Floating 

tenon blank 

assembly easier. I also cut it extra wide so I can trim 

the tenons flush after the frame is glued up. 

Making the tenons involves a little “two-step” 

between the router table and table saw. After rounding 

over one long edge, you’ll round over one end of 

the tenon blank, as in Figure 2. This way the tenon 

will seat tightly in the mortise. Then cut the tenons 

to length at the table saw. I clamped a stop block to 

the rip fence to size them identically (Figure 3). 

PANEL GROOVE. Now that the joinery is complete, you 

can cut the grooves to hold a panel, if necessary. 

ASSEMBLY. Finally, to assemble the frame, clamp it 

up like you see in the main photo. A pipe clamp 

pulls the joint together and a second clamp keeps 

it aligned. When the clamps come off, you can trim 

the tenons flush with a chisel and sandpaper. 

1 2 

a. a. 

Clamp stop 

block to 

rip fence 

THIRD: 

Cut tenon 

to length 

NOTE: Repeat 

steps until bit 

is centered 

SECOND: 

Rout one pass, 

THIRD: flip workpiece, and 

Adjust fence rout another pass 

toward bit and 

rout two passes 

with new test piece 

www.ShopNotes.com Page 3 of 3 ©August Home Publishing Company

Open Floating Tenon Joinery - gerald@eberhardt.bz

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