I'm curious if you have any photos of the install, or at least your process. I have a 7" riser, spider and bolts setting on the floor next to my BP. I've seen videos of guys putting a 3/4" round in their spindle, and support that with a shade under 3/4" hole drilled in soft vise jaws. Set the table low (probably at least 9" from the top of travel), align the vise jaws with the 3/4" rod in the spindle and tighten down on the rod. Use an engine hoist (I have a gantry crane) to grab an I-bolt on the ram. Remove the four 1/2" bolts from the turret, and lift the head off the mill with the engine hoist and the knee. Once it's up and out of the way, swing the head from over the base at the turret for better access; the spindle will rotate freely. Install the riser/spider, swing the head back over the riser and reattach.
The concern I have with this process is that it seems that you could be side-loading the bearings in your spindle as I'd never be able to simultaneously raise the knee exactly with the gantry crane. I thought about sticking a 1/2" drive socket in the spindle collet, and sticking a wobble extension into that. Clamp the other end of the extension in the mill vise. That'd put a universal joint of sort right at the bottom of the spindle. That might be a bad thing if the head decides to tip to the side; something about 2 points not determining a plane.
Another option I've considered is making a wooden yoke that fits around the casting just above the spindle. Lag that into a couple of 4 x 6" that are clamped to the table. Then the load would be on the casting, not the spindle bearings.
I've had the riser for at least 5 years; one of these days I've got to pick a horse and get it installed!
Bruce
