Good God! You really need to know what you are doing before you get hurt. Machining involves knowing feeds and speeds and what tools to use for what material (application). Also work holding is vital before the piece becomes a unguided flying object and per Murphy's law will be going in your direction. There is a reason that a journeyman machinist has a certificate.
All CNC moves in absolute are tied to part program zero. Incremental moves are tied to the last position. Thus in incremental a X move of 5 inches called up twice will result in a move of 10 inches. X5.0 called up again in absolute would return the cutter to 5 inches from X zero. This is a very basic concept.
And yes. If your machine is in inch and you try doing metric stuff you will quickly run out of machine travel.
Sorry, just concerned for your well being.
George
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)