The basic LPB tool is a ball, wheel or other similar tip that is supported in a spherical hydrostatic bearing.  The tool can be held in any CNC machine or by industrial robots, depending on the application.  The machine tool coolant is used to pressurize the bearing with a continuous flow of fluid to support the ball.  The ball does not contact the mechanical bearing seat, even under load.  The ball is loaded at a normal state to the surface of a component with a hydraulic cylinder that is in the body of the tool. LPB can be performed in conjunction with chip forming machining operations in the same CNC machining tool.
The ball rolls across the surface of a component in a pattern defined in the CNC code, as in any machining operation.  The tool path and normal pressure applied are designed to create a distribution of compressive residual stress.  The form of the distribution is designed to counter applied stresses and optimize fatigue and stress corrosion performance.  Since there is no shear being applied to the ball, it is free to roll in any direction.  As the ball rolls over the component, the pressure from the ball causes plastic deformation to occur in the surface of the material under the ball.  Since the bulk of the material constrains the deformed area, the deformed zone is left in compression after the ball passes.