We fabricate architectural millwork and store fixtures, and find ourselves using lock mitres on 3/4'' MDF columns for a paint finish. Many of the panels are 12 feet long, and at least 24'' wide, so the first cut is simple, on the flat with our shaper/power feed. The second cut must be done on edge, and it is at best a 3 man job and 2 passes, featherboards, etc. to get results. If only I had a shaper turned sideways? I have been looking at every conceivable machine, and at this point, a double end tenoner seems like the best fit. The cope head can be set level, and the machine is power fed. Does anybody have other thoughts? We have tried mitres with splines, rebates, biscuits, dowels, and the lock mitre works best for us, if we can do the machining. On smaller panels, perfect; large panels, who knows?
(Architectural Woodworking Forum)
From contributor P:
You might consider the lock miter that you run both sides of the corner through the shaper, then you create the groove on the table saw with a dado blade. Or just glue and tape like a miter fold. I would look into a miter fold machine before the tenoner.
The sled with the router spindle perpendicular to the panel (the "easy" cut) is small. It simply helps me start and exit the edge correctly. The sled for the router with its spindle parallel to the panel is wider. As I slide the sled down the edge of the panel, I hold down the "inboard" end to offset the weight of the router as it hangs off the "outboard" end of the sled.
With these, I move the tool instead of the panel. Because I am handling something small and controllable, I can make either cut by myself. I clamp a panel to my bench, run the appropriate sled down the edge, and I'm done.