First of all, don’t assume that the bed is twisted. A lathe with a straight bed does not need to be level. My suggestion is to fasten the bed to the bench with only three mounting points and washers under the mounting pads to keep it slightly up off the benchtop. Then use the Rollie’s Dad method to check the lathe for tailstock alignment and twist. Most likely, the tailstock is not centered on the spindle axis causing it to cut a taper. A dial indicator mounted in the spindle can help get the tailstock in the neighborhood of the spindle axis of rotation… maybe even within a half thou, or so, if you’re lucky. Then turn both ends of the longest test bar you can mount between centers to check for taper. If you have a taper that you can’t live with, keep adjusting the offset screws on the tailstock to try to remove the taper. If you still have a taper you can’t live with, you have a twisted bed and need to use a fourth mounting bolt, a precision level and shims to force the bed back into a straight condition. My 10F has been running on three mounting bolts for 10 years and turns true diameters within 0.001”over the full length of the bed. Remember that even a monster rigid lathe like the Mornach 10EE uses a three point mounting system. For a hobby lathe you don’t take heavy enough cuts to torque the bed. Even if you do take a hefty roughing? cut, you will almost always take a light cut to get to finish dimension. Most small lathes beds get twisted by bolting them to a stiff uneven surface with four bolts, not because the ways are not true. Finally, most jobs needing sub 1/1000” precision are done within a few inches of the headstock where bed twist is not a problem. Don’t over think the problem.

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