To display the Retract and Plunge dialog, click the Retract/Plunge button in the Milling tab of a surface milling feature.
Z rapid plane — Enter the minimum safe distance in Z above your part.
Before performing a rapid move away from a feature, the tool retracts to the Z rapid plane setting for that feature. The rapid move to the next feature changes in Z height, that is, changes Z coordinates, if the next feature has a different Z rapid plane setting. So that when it arrives at the next feature it is at the Z rapid plane for that next feature.
This value is relative to the top of your stock in the current user coordinate system. Compare with Plunge clearance.
Plunge clearance is the distance above a feature at which the tool starts to feed. In the case of deep hole drilling, the drill retracts to this distance between pecks. Compare with Z Rapid Plane.