Twist drill

  • US 8,540,463 B2
  • Filed: 08/02/2006
  • Issued: 09/24/2013
  • Est. Priority Date: 08/02/2005
  • Status: Active Grant
First Claim
Patent Images

1. A twist drill havinga shank,an axis of rotation about which the twist drill rotates during use, anda cutting tip, the cutting tip having a cutting edge which has an inner cutting portion forming a point having a point angle in the range 128°

  • to 160°

    , and a radially outer cutting portion that is inclined in the opposite axial direction to the inner cutting portion at an angle of from 2°

    to 8°

    with respect to a plane normal to the axis of rotation, said cutting edge being continuous over the inner and outer cutting portions and the outer cutting portion and the inner cutting portion abutting each other, the outer cutting portion being angled, relative to the inner cutting portion, such that the outer cutting portion leads the inner cutting portion in the rotational direction of cutting, the angle between the inner cutting portion and the outer cutting portion being in the range of being greater than 160° and

    less than 180°

    ; and

    the twist drill includes a cylindrical land and the outer cutting portion extends to the outermost edge of the cylindrical land.

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