I know I asked this before, but I'm not sure we really answerd the question- at least, not to the point I could grasp the concept.
I'm in the middle of converting the CNC lathe over to my new Centroid Acorn board (at least, as an when I have time) and to do it up right, it needs some home and/or limit switches.
I know a limit switch can be a fairly conventional- and not necessarily terribly precise- microswitch. That part's easy (other than trying to mount them away from chips, swarf and possibly even coolant.)
The "home" switches, however, need to be considerably more precise, as the computer takes that "home" position and bases distances moved off of it. If the home switch is only good for plus-or-minus five thou, the size of your part is only going to be good for plus-or-minus five thou, especially on multiple parts.
I also know that the home and limits can be the same switch, my question is, what kind of switch?
Lots of people recommend an optical switch- apparently a shutter in front of an emitter-detector pair is or can be sub-.001" accurate.
Most I've read about, however, are homebrew, and at this stage- that is, where I really still don't quite know what I'm doing - I kind of need an off-the-shelf solution.