Abstract: Perforating blades for perforating traveling webs of material such as paper in high speed apparatus are made from cold rolled steel which is hardened in a vacuum furnace to produce a scale free surface. The height to which the blades are ground is determined by measuring the average thickness of the blade and grinding the height of the blade to a dimension and tolerance in accordance with an equation which relates blade height to blade thickness. Thus the thickness of each blade can vary. With conventional knife rolls in which the blades form an angle of 45.degree. relative to a radial line of the knife roll, the sum of the height and thickness for each blade in the knife roll is equal.

Abstract: Perforating blades for perforating traveling webs of material such as paper in high speed apparatus are made from cold rolled steel which is hardened in a vacuum furnace to produce a scale free surface. The height to which the blades are ground is determined by measuring the average thickness of the blade and grinding the height of the blade to a dimension and tolerance in accordance with an equation which relates blade height to blade thickness. Thus the thickness of each blade can vary. With conventional knife rolls in which the blades form an angle of 45.degree. relative to a radial line of the knife roll, the sum of the height and thickness for each blade in the knife roll is equal.

Abstract: A cylindrical tube having eccentric inner and outer cylindrical surfaces is rotated in a lathe about the axis of its outer cylindrical surface. The thickness of the tube at a relatively small spot is measured by an ultrasonic thickness gauge whose sensing portion is moved relatively slowly along the length of the tube as it rotates to cover substantially the entire surface of the tube along a helical measurement path. A tool bit is mounted adjacent to the sensing portion of the ultrasonic thickness gauge for machining the tube as it rotates. The tool bit is moved toward and away from the center of the tube by a feed screw which is driven by a servo motor. The servo motor is controlled in accordance with the output of the thickness gauge to control the depth of the cut made by the tool bit in direct proportion to the measured thickness of the tube wall adjacent to the tool bit, thereby reducing the eccentricity of the tube.