I've got the bug too. I'm currently limited to a 17" swing lathe and have set aside a couple of projects that require more.
I'm not chiming in on your request enginebill, unless someone within 100 miles has a really cheap one for a cheap guy.
I'm not even dreaming of a 40 incher with a perfectly concentric NMTB 50 "chuck" holder, so putting it together will be a challenge but I like challenges.
I'm checking heavy equipment salvage yards for a
big engine flywheel. Engineered for respectable RPMs and resistance to distortion by a heavy clutch.
My thinking goes; "the flywheel was concentrically and substantially affixed to a crankshaft so just turn a 50 NMTB taper with a flange that duplicates the crankshaft end and provides for locking down on the four threaded spindle holes." That means having exposed fastener heads on the face of the faceplate, so that the holder may be bolted up to the spindle first, the faceplate going over it.
Dropping the table of my K & T 2H universal would allow up to a 48" swing and enough Y movement for the faceplate and several inches of workpiece. For smaller diameters, (that clear the lowered table, 32" in my case) the part could be quite a bit thicker and still allow a tool holder some table for attachment.
As in any project that seeks to maximize the envelope, the operator must exercise caution and reason as he approaches the limits.
Bob
