I was making some storage boxes for the basement and thought I'd try out a lock miter router bit. I had some hardware store cedar planed to 3/4" left over from another project so I tried that. Using the recommended router speed and setup block the inside of the lock router cut was very rough with a lot of tear-out along the cut. I used a backing piece to prevent tear-out at the end of the cut. It didn't seem to matter much if I took several small passes, a couple of medium passes, or did the whole cut in one pass. I used a miter slide for the horizontals and a mortise jig for the verticals and vibration was not an issue. I'm guessing that cedar (or white pine for that matter) is too soft / weak to stand up to the kind of simultaneous cross-grain cutting on different levels that the lock miter bit produces. Has anyone had particularly good luck with lock miter router joinery and if so, what woods worked for that?
Thanks, Bob Kirkpatrick