How to Add Splines for Stronger Box Miters
A quick-to-make spline jig produces clean joints with hidden power.
Synopsis: Splines are a well-known technique for adding strength to miter joints, but there are times when a visible spline spoils the look of a box; for example, when you have carefully matched grain wrapped around all four sides. That’s when Doug Stowe uses hidden splines, tucked into slots routed into the miters. A simple spline jig makes it easy. Learn how he does it, along with tips for assembly and glue-up.
When making mitered boxes, I carefully select the stock for its character and grain, which I like to wrap around all four sides. Splines help me bolster the joint by adding long-grain glue surface. Cutting them into the box’s outside corners after assembly can interfere with the wood I have so methodically selected. That’s why I often tuck the splines into slots routed into the miters.
These joints are easy to cut with the right…