[DonRotolo]

If the lines are more than 0.100 apart, you'll end up with grooves and not a surface.

One might use a 0.250 bit, separate the lines by .250 (maybe .249) and drop down .250.

Just remember that you need to consider what the bit can cut: At that outermost line, you've dropped down by an inch, right? Can your bit cut a whole inch at a time? If not, how might you address that issue?

This is one reason it is often better to learn how to use a manual mill before getting into a CNC mill. Understanding the milling process is critical.