Bolster (and Beautify) Basic Butt Joints
The butt joint embodies simplicity, but can fall flat on strength, especially when end grain or thin stock are involved. Splines and bowtie keys (shown here) reinforce and add elegance to the joint while assisting with alignment during assembly. Here's how to add both elements.
Tablesawn splines keep clean lines
To add this detail to your project, first mount a tall extension to your tablesaw's miter gauge. Then, determine the position and length of the splines. Use your tablesaw's fence to locate the first spline, and then raise the blade to half of the spline's length. Make the mating cuts in all pieces before moving the fence or adjusting the blade height [Photos A, B].
Cut spline stock to fit the kerfs [Photo C]. To help with alignment during the final assembly of the joint, glue the splines into only one workpiece at a time and let dry before gluing the mating piece in place.
Bowtie keys add a touch of class
First, mount a dovetail bit in your router table. (The bit diameter and cutter angle don't matter.) With a tall extension fastened to your router table's miter gauge, adjust the fence to center the bit on your workpiece and rout the dovetail [Photo D]. Repeat for the other half of the joint on the adjoining piece [Photo E].
Make the perfect-fitting bowtie
Now, plane a blank of contrasting wood so its thickness matches the width of the dovetail bit. Crosscut the blank to a length twice the depth of the dovetail slot. Without changing the bit height, move the router table fence to cover half of the bit's diameter. Make repeated passes along the length of the bowtie-key blank, flipping the piece end-for-end and over until the bowtie is fully shaped [Photo F].
Check the bowtie-key blank's fit in the frame's dovetailed kerf. If the blank is still too wide, nudge the router-table fence back to expose more of the bit and make additional passes until it fits. Rip a key from the blank and glue it in place [Photo G].