Contributed by Larry Thomson -- August 2016
"The box I was working on is a backpackers registration box for Grayson Highlands state park -- it sits outside the contact station so late arriving hikers can register -- on the left side are the blank forms and the completed form is put in the right side -- the Appalachian trail runs thru Grayson Highlands so they have a lot of day and overnite hikers come through -- the old one was falling apart -- the only routing that was not done using the Router Boss was the round over on the front cover -- as you see -- i even did the knob with the Router Boss 4th Axis setup."
NOTE that the mitered corners were cut by Larry using a lock miter bit and the front knob was turned on our 4th Axis Work Holder. See below for easy to follow instructions on the lock miter joint.
The Craftsman Gallery instructions for cutting a lock miter joint on the Router Boss:
In addition to the lock miter bit, our procedure requires the optional depth digital readout (DRO) kit and riser plate with fence kit plus the included stops and aluminum router plate guides. Both mating boards must be the same thickness. On the Router Boss the 2 required settings are for: (a) depth of cut and (b) thickness of the boards.
a) With one of the boards clamped flush to the fence and bottom of the base plate, zero the bottom of cutter on top of the wood and set the depth DRO to zero. Divide (thickness of the wood + cutting length of the cutter) by 2 to get the plunge depth. This setting will put the center of the cutter at the center of the board. For example, if the vertical cutting length of the bit is 1" and the boards are 3/4" thick then the plunge depth is 7/8". Move the bit away from the wood then plunge the bit to this depth as measured by the depth DRO. Lock your plunge router at this depth.
b) With the clamped board still flush against the fence and bottom of the base plate, bring the bit forward to zero the cutting edge of the cutter against the edge of the wood and lock the router plate at this position. Then use the mating board as a gauge to set a stop in the guide rails that will allow the router plate to be moved forward the exact thickness of the board. Remove the clamped board, bring the router forward to the stop and again lock the router plate. Your setup is now complete.
Cut one board edge by feeding the board edge horizontal through the cutter then cut the mating board edge by feeding it vertical through the cutter. This may require feather-boards or other means to support and keep the work piece against the fence and base plate. Do not climb cut if you hand-feed. If you have our mortise table, you can clamp the wood to the mortise table t-track when it is mounted vertical or horizontal without the back spine and machine-feed the boards through the cutter.
You should make a trial cut in scrap, but the above setup will result in a close to perfect joint. This setup is much easier and more precise than the typical setup on a router table and it works with any lock miter bit. It takes away the "hit or miss" challenge.
If you experence break-out from the cutter, you can help eliminate the break-out with sacrificial fences. Close the gap between the fences then cut through the closed fences with the lock miter bit when bringing the router forward to the stop or final position. This provides zero clearance between the cutter and the fence.