*indicates optionalG90 O.D./I.D. Turning Cycle:  Rapid,  Feed,  Programmed path,  Cut allowance,  Finish allowance,  Start position,  Target.
G90 is used for simple turning, however, multiple passes are possible by specifying the X locations of additional passes.
Straight turning cuts are made by specifying X, Z and F. By adding an I value, a taper cut is made. The amount of taper is referenced from the target. That is, I is added to the value of X at the target.
Any of the four ZX quadrants can be programmed using U, W, X, and Z; the taper is positive or negative. The following figure gives a few examples of the values required for machining in each of the four quadrants.G90- G92 Address Relationships