Lock Miter Setup Jig
A lock miter is an excellent joint for building boxes and small cases. It creates lots of surface area for glue and a tight mechanical fit—the two requirements of any good woodworking joint. There’s one big downside, however. Setting up a lock miter bit in a router table is a pain. A new jig from Prazi, the GrooveCenter, makes the process much easier.
With a lock miter bit, one of the parts is routed horizontally, lying flat on the table, while the other is routed vertically, standing against the fence. You use the same fence and height settings to cut both parts. (You can’t cut one part, readjust things and cut the second part to fit.) Both the fence and height settings need to be accurate to within a few thousandths of an inch. Usually, that accuracy requires a lot of trial-and-error cuts; the GrooveCenter nails both settings much quicker.
The GrooveCenter was initially designed to quickly position a router table’s fence for cutting grooves or mortises precisely in the middle of any stock. It performs that task quite well, but the folks at Prazi also realized that their device, with the addition of a depth gauge, could also be used to quickly set up a lock miter bit. You can see how the jigs works by watching a video at Prazi’s website. The GrooveCenter has an adjustable stop to accommodate each major brand of lock miter bit.
Prazi USA, praziusa.com, 800-262-0211, GrooveCenter, PR-6000, $149; 2-Axis Depth Gauge, PR-6500, $49.