Method of polishing uniform or free-form metal surfaces

A method of automatic finishing of a free-formed contoured metal or hard die surface, comprising:

• (a) providing a rotating brush with a central hub carried by a driving spindle for rotation about the hub axis;
• (b) providing said brush hub with a plurality of closely spaced, resilient and flexible free-standing nylon filament strands possessing abrasive polishing particles, said filaments having a uniform diameter in the range of 0.02-0.04 inches, each strand being secured at one end in the hub and having sufficient stiffness in a static condition to have its other end standing radially away therefrom to present an apparent curved surface of closely packed strand ends having their outer extremities in a touching relationship;
• and
• (c) rotatingly driving said hub and strands at a constant torque in the range of 40-60 newtons while dragging the ends of said strands across said die surface, while in contact with such surface to effect the desired degree of polishing, said hub being driven by an electric motor carried on a computer positioned assembly, and wherein a closed loop feedback central, in connection with the motor and assembly, causes the assembly to move in response to sensed torque of the brush for restoring the torque to a constant value, the attainment of constant torque being achieved by modulating the output torque of the electric motor spindle rotatingly driving said brush and by raising or lowering the brush relative to said surface.