I agree with everyone else:
Supervise all tool use and any event that carries risk.
If CNC tools are involved:
(D)emand the removal of all distractions when locating or doing setup.
(I)nsist on comments in G-code or clear mechanical drawings.
(R)emove the tool and execute the G-code clear of the work piece.
(T)est all examples with simulation when totally in doubt.
(E)stop should be where your hand is during a dry run.
Anyone that has coolant - eventually that's a different kind of dirty
