Patents Assigned to P.L. Robertson Manufacturing Co. Ltd.
  • Punch for making recessed screw
    Patent number: 3972083
    Abstract: A tapered punch for producing a recessed screw, the punch having an axially extending recess forming portion of symmetrical cross section and presenting in cross section 8 symmetrically disposed corners in 45.degree. spaced relation with any 4 alternate corners lying on the corners of one square and the remaining 4 alternate corners lying on the corners of another square in 45.degree. angular relation to the first mentioned square, and a method for cold forming the recess by evenly spreading flow of the metal.
    Type: Grant
    Filed: January 13, 1975
    Date of Patent: August 3, 1976
    Assignee: P.L. Robertson Manufacturing Co. Ltd.
    Inventor: Geoffrey Dreger