tool height

I am interested in making a tool touch-off part for my mill. Acorn has an easy interface which basically is a one-wire input; you use a standard height (I use the KP-3 probe) and then reference everything off it as a relative height. Although you can buy a factory made tool touch off system...

I started learning to use a manual lathe towards the end of the last year and I have seen conflicting advise for the proper height of lathe tools. Often, I see a forum post with advise along the lines of "at center or slightly above" but I have also seen the opposite of "at center or slightly...