I'm in the process of making a custom vacuum table that will have accurate stops for positioning stock and custom spoilboards. The spoilboards will be 1/4" polycarbonate because that's what I have lying around and it seems like they'll work.
What I want is a way to quickly get the machine zeroed to the vacuum table at startup. My homing switches are not it, obviously, and I don't own any fancy pants probes. I'd like to build something into the vacuum table itself to make zeroing it easy. For instance, an empty cylinder where I can lower an end mill, then use calipers, measuring the distance on X and Y between the shaft of my end mill and the cylinder walls to ensure that it is centered in the hole (assuming vacuum table has zero rotation).
Any other ideas? Ideally I want to be able to do this without tool changes. I don't want to use wobblers or anything like that. I like the idea of calipers.