Drill for use in drilling hard and brittle materials

A drill for use in drilling hard and brittle materials, comprising:

• a shank adapted for attachment to a shaft of a machine;
• and
• a drilling portion attached to one end of said shank and including a tapered primary cutting edge located adjacent to a center of rotation of the drill, a first secondary cutting surface extending from said primary cutting edge and having an angle of taper substantially identical to that of said primary cutting edge, and a second secondary cutting surface extending from said first secondary cutting surface and containing a line substantially parallel to a central axis of the drill;
• said primary cutting edge having a first abrasive grain layer, and said first and second secondary cutting surfaces both having a second abrasive grain layer,
• said first and second abrasive grain layers both having a binder made of a material selected from the group consisting of metal, resin and glass, and
• each abrasive grain in the first abrasive grain layer located on said primary cutting edge having a diameter greater than that of each abrasive grain in the second abrasive grain layer located on each of said first and secondary cutting surfaces.