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At our weekly staff meetings, I usually don’t have much to say. Our staff is comprised of knowledgeable people who know a lot about woodworking; our cumulative knowledge is deep. But, we all come from different backgrounds with very different experiences and sometimes those ideas cross each other.
So, at this week’s meeting, when Glen Huey mentioned his blog post about lock-miter joints, saying he’s not a fan of them, I opened my mouth and said that I like lock-miter joints. That raised a couple of eyebrows, and I was asked to put my opinion in print , good one, Jim.
My woodworking background covers a lot of areas simply because I worked in several different commercial cabinetmaking and furniture making shops.
At one point, I worked in a very large cabinetmaking shop that took on only the biggest jobs , casework for an entire motel, all the fixtures for huge department stores, all the furniture for a new college dorm , you get the idea. I was hired to build “custom” store fixtures. The crew I was in charge of only had to make six to 12 of one fixture, as opposed to the production line that cranked out hundreds of cabinets in a single run.
OK, OK, I’m getting to my point.
We made our store fixtures out of veneered plywood and clear (non-veneered) MDF (that would receive a painted finish). When I got the cutter set up to make a perfect lock-miter joint, I would run miles (it sure seemed like it) of these joints on our monstrous shaper.
At assembly time, the joints would self-align perfectly , we needed to clamp from only one direction. Some of these joints were up to 10′ long, which made the self-aligning factor all that more valuable. And, as Glen mentioned, the gluing surfaces on a lock miter are large, which is good when using sheet goods, especially MDF. Only light sanding was necessary to make the corner of the joint invisible.
Another advantage when cutting the lock-miter joint is the fact that lots of parts with different widths and lengths can be run through the same setup. Cutting 45�° bevels on a table saw is fine if you have like-sized parts. It gets complicated if they differ in size.
Setting up a lock miter cutter is no more difficult than setting up stile-and-rail cutters on your router table. Some trial and error is necessary, but once you have the perfect setup, all you have to do is save those samples for future setups.
True, with the lock-miter cutter, one part is run flat and the mating piece is run vertical, but with help from some featherboards, this task is easily managed.
Using lock miters to make quadrilinear posts is easy , run two opposing parts flat and the other two vertical. Glue up requires clamping in one direction because the lock miters self align, as shown in the illustration below.
As a bonus, lock miters are also useful when constructing drawers or boxes to show off the joint using woods with contrasting colors (check out the beauty shot at the top).
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I also worked in a large shop that did hotels and point of purchase displays and trade show exhibits. We used a locking miter in a shaper that we dedicated to just that bit. We also build a triple router table for raised panel doors that was always set up with the cope and stile bit and a 1/4" straight bit. both of these machine setups made life easy and the only time we messed with them was to change bits to be sharpened.
Thanks Joey
Lock miter bit setup needn’t be trial and error. One test cut is all you need to set up this bit. For an explanation how to do this, send an email to wedlock@alum.mit.edu requesting my Lock Miter Bit Setup article.
Bruce Wedlock
The initial set up gave me fits, but once accomplished, it was easy going.
Good article Jim.