I am getting these proximity sensors:

http://web6.automationdirect.com/adc...ies)/AM1-AN-1H

I have an X3 mill from grizzly and Bob Campbells Mach 2/3 breakout board.

http://www.grizzly.com/products/G0463/images

http://www.campbelldesigns.com/breakout-board.php

I want to have home and limit switches.

Now here are my questions.

1) how many proximity sensors do I need?
2) where do I put them on my X3?

thanks a lot,
Nick