Cutting miters by hand using my miter box gets me close to the final length on small workpieces. But it doesn’t quite get me the perfect fit I’m looking for.
To produce tight-fitting miter joints on small parts, I made the small parts miter trimmer shown above.
The construction of this small parts trimmer is pretty simple. It consists of a two-piece hardboard base, a 90° fence, and a bottom cleat. The upper base aligns the plane as it trims, and the lower base has grooves for keeping chips out of the path of the plane.
The fence is built from two pieces of 3⁄4"-thick hardwood with 45° miters on both ends. The key to getting perfect miters with this trimmer is installing the fence so it sits at a precise 45° angle with the base. (Note: A combination square is a good tool to use to position the fence.) Also, it’s equally important that the ends of the fence line up flush with the edge of the upper base.
The last part of the small parts trimmer is a 3⁄4"-thick hardwood cleat. It fits against the edge of the bench, holding the whole assembly in place during use.
After the pieces are glued together, attach sandpaper to the fence to keep workpieces from slipping. Then, it’s just a matter of trimming the mitered ends of the parts so they fit tight.
This handy jig makes it easy to hold a piece at a 45° angle while shaving the mitered end with a block plane.