My new endmill came in today. I've had a couple problems with stuff rotating on the dividing head under cutting load, making a mess. I diagnosed the problem as cutting forces causing the chuck to unscrew. Wish I had held out for the Hardinge taper head instead of the old threaded unit.
I'm going to try a LHC end mill to see how that works. I wired up the original controls as signal inputs to the VFD, so reverse now works via the VFD. Here's hoping...
Of course, a milling cutter on an arbor is easy to reverse. Just stick it on the arbor the other way. I just don't have a cutter large enough in diameter for this job, and they're expensive.