The standard Woodsmith method for creating frame and panel assemblies has been stub tenon and groove joinery. In this approach, the thickness of the plywood panel drives the size of the groove and the matching stub tenons. I’ve been taking that process one step further. Why not use plywood splines instead of a separate step to make stub tenons? The concept is similar to loose tenons or biscuits.
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| A slot cutter turns your router table into a joinery workstation for simple, strong assemblies. |
Related to this, I’ve noticed that MDF core plywood measures very close to 1/4". This means you can form the groove in a single pass with a dado blade, or in my preference, a slot cutter in the router table.
There’s another advantage lurking here. Since you don’t need to create an integral stub tenon, sizing parts is simpler. They’re based on direct measurements and no accounting for joinery. This allows you to concentrate on accurate crosscuts. Forming the joinery details won’t affect the length of parts.
STRAIGHTFORWARD LAYOUT.
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| Mark a triangle on paired stiles and rails, with the apex point toward the top, to keep the parts oriented correctly for joinery and assembly. | Setup blocks offer a physical reference point for setting router bits to the correct height. | Using the router table fence along with the bearing on the bit provides a smooth entry and exit of the workpiece as it is cut. A steel rule helps you see when the two are aligned. |
In this joinery method, power tool setup replaces detailed layout marks on the workpiece. Your focus here is making sure to cut those details in the correct edge and end of the parts.
The way I learned to do that is to mark a triangle on matching pieces, as shown in Step 1. Arrange the frame members how you want them to appear in the final assembly. Bring the two rails together and draw a triangle across the two parts. Repeat this for the stiles.
The triangles tell you a lot. The tip of the triangle points to the top of the assembly. The edge that the triangle crosses is the inside edge of the frame. And when I’m standing at the router table, the triangle tells me the appropriate face is up. It’s like a secret code.
ROUTER TABLE SETUP.
At the router table, I install a 1/4" slot cutter. The bit’s height is determined by a setup block (Step 2). I’m using a 1/4" block here to center the groove in my workpieces. Since the groove is cut in a single pass, an exact center isn’t something you need to fret over.
Now it’s time to bring in the fence. Position the fence to align with the bearing on the bit, as you can see in Step 3. I have it set for the maximum depth of cut, 1/2" in this case.
ROUTING GROOVES.
With the router table programmed, the actual routing is basic work. I use push pads to provide consistent pressure as I rout along the inside edges of the stiles and rails. The ends of the rails receive grooves, too. For this narrow cut, I use a backer block to keep the piece square to the bit and to stop tearout. This is shown on the previous page.
ASSEMBLY
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| Arrange the parts of the assembly prior to glueup so that they’re in the correct orientation. |
The photo series above walks you through the assembly process. In the upper photo, I’ve set out all the parts that need to come together and in their correct orientation along with the four splines. The splines are cut a hair narrower than the combined depth of the grooves. The shoulder of the joint will close tight with a barely there gap on the end.
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| Apply glue to the slot on the end of the rails and insert the spline. Allow the glue to set up before proceeding. | Run a bead of glue into the grooves in the two rails then fit them over the ends of the panel. |
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| The final step in the process is to bring in the stiles. After brushing glue onto the exposed splines, add more glue to the groove in the stiles. | Draw the clamps tight to close up the joints. Trim the exposed splines flush after the glue dries. |
THREE PARTS.
I divide the glueup into three stages. The first is to glue the splines into the ends of the rails, as in Step 1. Make sure that the splines don’t extend past the bottom of the groove. Otherwise the panel won’t fit. Allow the glue to set up for 20-30 minutes. Now the splines act like integral tenons and you have fewer loose pieces.
The second step is to glue the rails to the panel. This this is shown in Step 2. The edges of the splines and panel should align, or the panel can be slightly inset.
The final stage is to glue this center section to the outer stiles, as in Steps 3 and 4. As you tighten the clamps, be sure the faces are flush. You need just enough clamp pressure to close the joints.
PRIMED FOR CUSTOMIZING
The process that I’ve outlined creates a square-edge assembly that blends in with a lot of styles. It doesn’t have to end there. Think of it as the base model ready for a custom trim package.
The photos on the next page highlight a couple of options. Best of all, these details are created with common, inexpensive bits you probably already have. Feel free to use those ideas, but consider them as representatives of a range of other paths to take.
CUSTOM MOLDING.
A dramatic bolection molding flows over the inner edge of the stiles and rails and onto the panel. This expressive molding adds depth to the whole assembly (Steps 1-4).
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| Cove & Bead. Rout a large, complex profile along each edge of an extra-wide blank. An ogee profile would work as well. | Complete the Circle. A point cut roundover bit forms a bead at the top of the profile ending with a fillet. |
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| Make The Step. A straight bit cuts a groove that matches the offset between the frame and the panel. | Rip & Miter. Cut the molding free of the blank at the table saw. Then miter pieces to wrap around the frame. |
SIMPLE, SUBTLE.
The lower photos show a second option. Here a small, applied bead molding tucks into the junction of the frame and the panel.
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| Just Bead It. Rout a bead profile on oversize blanks. Rip thin strips from the blank and miter them to wrap around the inside of the frame, as shown at left. |
It’s helpful to focus on one aspect of woodworking in order It’s helpful to focus on one aspect of woodworking in order to master details. What I’ve tried to do here is to show how one technique opens up opportunities for consistency, confidence, and creative expression.
