Abstract: An improved pump is provided for pumping non-lubricating fluids at extremely high pressure while reducing galling and wear on components such as pistons and cylinders. The reduction in component wear and galling is achieved by modifying the piston-cylinder combination to provide a pressure area and a centering area that is axially displaced from the pressure area of the piston-cylinder combination. The pressure area of the piston-cylinder combination is modified by reducing the diameter of the piston or increasing the inside diameter of the cylinder or both to provide a 0.1 percent to 2.5 percent increase in clearance at the pressure end of the piston-cylinder combination than is provided at a centering area. The advantages of the invention are further enhanced by employing a release area disposed intermediate the pressure area and the centering area of the piston-cylinder combination.