Hi Nick

If you hit a limit switch on a cnc mill the part is probably going in the bin, so we never hit limit switches, they are surplus to requirement :heehee:

So any limit switches fitted are actually homing switches and your only priority is repeatability. It must always switch at the same position. Reed switches can't do it. Microswitches with rollers allow the tool to pass by but the lever costs you precision. You don't want to ram into a solidly fixed microswitch because you will have enough driving force to crush it flat. Best way to fit a microswitch is to spring something in to it holding the pip down, then have the slide hit that something allowing the pip to rise. Microswitches always have change over contacts so NO/NC is a permanent option.

If the G00 fast feed isn't ultra quick, waiting while the tool winds all the way to the end and back is a pain, so a moveable switch is good for the X.

OTOH, do you really need them? Pretty useless on a round column mill. Pretty useless unless you are mass producing with a fixed jig to hold the job. Positioning switches might be useful if you had a whoopsy and lost position, but you do your best to avoid that.

A Z switch could be handy for tool changes, but there are simpler solutions.

Robin