I now have one of those spiffy probes with the little, tiny ball end, and the switch consisting of the three little arms at 120 degrees apart, resting on ball bearings. In terms of precision and repeatability, it's excellent - I get very consistently +/-0.0001". But, I have two problems:
1) It's near impossible to get it calibrated to where the ball end is *precisely* aligned to the spindle center. Getting much under +/-0.0005" is a real chore, and I'm not at all convinced it'll stay there for any length of time.
2) Even worse, the distance the probe tip moves between the time it first makes contact with the workpiece and the time the switch opens is completely unknown, and, I suspect, due to the gemotry of the switch, probably varies based on the angular position of the contact point.
So, how in the heck are these two problems resolved? Certainly, it would work just fine as-is for probing an object to get a point cloud, but I want to use it for machine setup, so I have to know *exactly* where the spindle centerline is relative to the contact point, as I did when I used to use a rigid probe (which Mach3 liked to break off from time-to-time....).
On a related note, I'm working on a "semi-rigid" probe design that will have a 0.200" diameter tip just like the rigid probes I've used, but will ber able to "give" on over-run by having the probe mounted in a spherical ball bearing, with a spring-loaded centering mechanism. I think this will be far easier to adjust perfectly concentric to the spindle, and should return precisely to that position after being bumped off-center.
Regards,
Ray L.