Nope were not using earth ground here sir, it`s OK if the power company`s transmission lines all the way down to the household service drop have an earth ground, but if it`s not then we have a huge problem when lightning strikes, that means if I put an earth ground on the CNC machines then if lightning strikes on the electrical grid, the machines with an earth ground wires will be fried and toasted I tried it in some communication systems here in our place and it`s not good, (I fried a repeater once) maybe in the US, europe, japan electrical standards that`s OK but here in the philippines it`s not really advisable sir rather it`s dangerous. It could burn your house if the lightning strikes.