No, there's no fixed rule like that.Thanks. That looks like a great option for me if the quality is right. It's both affordable and modular. I like the idea of being able to upgrade the mounting plate and the motor to fit my needs. I also like the idea of a made in America product from a company that would stand behind their product.
Do you own this unit yourself?
[Actually, I have several of them. Taig uses the manual version as a basis for their 4th axis, putting on their own base-plates and motor mounts.]
How would you mount a 2" x 6" x 12" slab of aluminum (or wood) as the work piece with a unit like this? Would you attach tubes on either side (of the blank stock) to fit the chuck and tail stock? Or would you mount something else (instead of a chuck) to the mounting plate? I have seen work holders on wood lathes that look like round plates with nail spikes sticking out to grip larger slabs of wood for turning.
[Those are called headstock spurs. They work well for soft woods, but not on aluminum. The easiest way to do this is to screw a square-section piece of stock to the headstock end of the workpiece and hold that in a 4-jaw chuck. If screws can't be used, you can also cut down the workpiece to a square stub that fits the chuck. I've also done more elaborate fixtures, like a tapered dovetail mount that accepts a dovetail screwed to the workpiece, but that took some machinery to build.]
I am trying to figure out if a 4" or 5" chuck is sufficient for what I intend to work on or if the chuck diameter has to (at least) match the diameter of the blank stock.