I've been wanting a tool setting probe for my mill for a while now. It makes changing tooling a no brainer and also allows for high accuracy. These things are expensive however, so I watch eBay. After over a year of waiting, one came up for sale for $80. I went for it in spite of 3 strikes against the eBay add -
It was covered in a rusty dust and had a very funky protective flexible conduit attached. I removed that and washed the whole unit. I inspected the flex seal in the nose and everything looked really good.
The next thing to do was to test the contacts - I hooked up the DVM and tested the Red/Blue pair. Everything looks fine.
Looks like I got myself a probe.
Now all I need to do is source a waterproof conduit and the fittings to seal to the probe, mount the probe, run the conduit, mount the interface card, figure out where to add the probe signals to the machine I/O and calibrate and test it. It'll take weeks, but I'm pretty interested in getting it in.