I do ride the short bus.
Two lathes in my shop. I have a Penmaster by PSI mounted to 5/8 plywood, the plywood screwed to a saw horse and that one is working good.
The other is my problem child. 1980s vintage B&H, 57" ways, 1 hp motor. Total length is 72 inches counting the motor. I have no factory parts below the ways, it is a 'benchmount.'
I have it on a 2x4 frame screwed to the wall studs of the house, 2x4 legs, with doubled 3/4 ply for the surface, and some extra weight (2 cinder blocks) on the mounting surface. It's jiggling, unloaded, like a hotel bed from the 1970s with a quarter slot mounted to the headboard. The tailstock isn't too bad, but watching the surface of a cup of water straddling the ways at the headstock end makes me seasick.
I am trying to turn a 35" piece of white oak from 5/8 up to 9/8 and then back down to 5/8 over the 35" run. With my hollow ground skew honed to 4k on DMT and stropped, with three steady rests in use, it looks like a barber pole.
The lathe, as most early 1980s hardware, has mixed SAE and metric fasteners on it. I am suspicious of the bearings in the headstock and motor, but also suspect the bearings might be no longer available.
My tentative plan is to remove the wallmounted shelf; and build a 6 foot workbench to mount the lathe to, 6" thick birch at 24x72 is 6 cubic feet, the top alone should come in around 258#. I have a ton of basalt in fist to volleyball sized chunks and should be able to crate or bin another 800# on the lower shelf easily with an undercarriage of 4x6 Doug Fir. One ton of basalt from my local rock quarry was $16, but two trips with my truck to bring home.
At what point is my bench stiff enough and heavy enough to be looking at the bearings in my motor and headstock rather than adding more weight?
Thanks.