Abstract: This invention aims at avoiding interference of a blade when a plurality of grooves of a diffraction grating element are formed. In order to achieve this object, in a method of working a diffraction optical grating element shape on a working target surface, a main spindle for rotatably supporting a cutting blade is provided on X-, Y-, and Z-coordinate axes of the working target surface, and an angle of an edge of the cutting blade mounted on the main spindle performs working to have an inclination with such an angle that interference with a planned working position at an outer peripheral portion of a curved surface of the diffraction optical grating element is avoided.

Abstract: An internal flash removal unit which radially cuts flash while it is still hot and relatively soft. A drive motor and reduction gearbox mounted in a housing drive a tooling plate rotatably mounted on the housing. A cutting assembly is mounted on an arm which is pivotally mounted on the tooling plate. A hydraulic actuator causes the arm to move outward and place the cutting assembly into cutting position as rotation of the tooling plate begins.

Abstract: Apparatus for underfiling curvelinear vanes of cast centrifugal impellers. Such vanes are cast with generally uniform thickness along their length; it is desirable to have the vanes taper in thickness such that the radially outward portions are thinner than the roots; also this provides a desired curve to each side of the blades.