Which Type of Limit Switch

[Clive S]

I f i read it right, this unit you recommend is fixed on the mill bed and a peice of metal is attached to each axis, the metal inserts between the 2 posts of the switch and makes the contact?

Yes its an optical switch that is to say an invisible beam of light it being shone across the gap in the sensor and then when use pass a piece of dark plastic or metal into the gap it breaks the beam and triggers. ..Clive