Abstract: A method and apparatus for enlarging a bore in a work piece including means for sealing the bore, a source of hydraulic fluid and a hydraulic pressure amplifier for introducing the fluid into the cylindrical bore and amplifying the pressure of the fluid to a value exceeding the yield strength of the work piece, thereby forcing the walls of the bore to yield until the bore reaches a predetermined diameter. The hydraulic amplifier means includes a plurality of series connected cylinders of increasing diameter so that the fluid acting on each cylinder is multiplied by the pressure of the preceding cylinder.

Abstract: A hydraulic power system having a plurality of variable displacement pumps for supplying pressurized fluid for manipulation of an implement includes a control system operative to automatically adjust pump displacement to the output horsepower of a prime mover driving the pumps of the system. The control system includes underspeed valve means responsive to a deviation in the speed of the prime mover from a predetermined normal speed and a selectable second speed to transmit a fluid pressure signal to a servocontrol means for adjusting the displacement of the pumps. The control system includes a valve for selectively conditioning the control system to cause the underspeed valve to respond to a deviation of the selected engine speed and an indicator for indicating the conditioning of the control system.