Video: A Better Joint for Beaded Casings
Jack miters are part butt joint and part miter, and they can be cut by hand or production-style with a router and shop-made jig.
The first time I saw a jack miter was in Roe Osborne’s bathroom. Roe was my editor at the time and I was on my first trip east to visit the crew at Fine Homebuilding. What I noticed was that the corners of the beaded casing on the doors and windows weren’t mitered. At least they weren’t mitered in any fashion I’d ever seen. I soon learned that the joint was a jack miter: The quirk-and-bead profile is cut at 45˚ to create a miter with the mating piece, but the flat of the casing is cut square, to make a butt joint. This way of joining casing is definitely more involved, but it’s also more likely not to open up as the wood moves. And though you can cut them by hand, you can also use a router and jig to speed things up.
Check out this video and my article, “Two Ways to Cut Jack Miters,” in FHB #277 to learn how to do it both ways.