Twist drills

A twist drill having a longitudinal axis and a cutting tip;

• a plurality of flutes extending helically longitudinally of the drill and having leading and trailing front edges at said tip;
• a chisel edge at said tip of the drill;
• lands located between the flutes, said lands comprising primary lands extending helically of the drill and at least one secondary land associated with each primary land and extending helically of the drill in circumferentially spaced relation to the rear of its associated primary land, a cutting tip comprising major flanks, each formed by said leading and trailing front edges of adjacent flutes, adjacent land and adjacent chisel edge, each of the primary lands being relieved for a limited distance from its adjacent major flank to form a minor flank;
• the leading front edge of each flute and the intersection of the flute with the minor flank defining a drill cutting edge which extends into the periphery of each primary land at a smaller radius from said longitudinal axis than it extends into the periphery of the associated secondary land so that each secondary land forms a sizing flank for taking a skimming cut following the cut taken by its associated primary land.