[diyengineer]

At work we touch off a series of ring gauges to check for accuracy and repeatability. It also gives us a history on how the machine has been running, i.e. are these numbers growing, shrinking, has something changed after maintenance was servicing the machine, etc. I was thinking about setting up a couple on my machine bed to test it out and use the same concept. Anyone else doing the same, or using 1-2-3 blocks?

Thanks.

[RomanLini]

I use hall-effect home switches on X and Y, which allow homing of the machine very accurately, and even do that at different times to "trim out" thermal expansion of the machine.

There's a thread on the electronic hall-effect home switches here;
http://www.cnczone.com/forums/open_s...made_easy.html

As for the height, I use a home made mechanical height sensor that goes under the cutting tool. This is also highly accurate and I run this after each tool change to dial in the new tool height (of course) and also sometimes to trim out heat expansions of the machine and router shaft etc.

Then as far as height to the job, that is referenced to the table surface which remains the same so all Z coords are tool > table surface which is 0.