Twist drill for advanced materials

A method of drilling a composite material containing fibres, wherein the method includes the step of drilling the composite material with a twist drill comprising:

• a shank;
• a drill body;
• a drill tip including a pilot, a cutting edge, a primary facet extending behind the cutting edge and a secondary facet extending behind the primary facet along a length of the drill tip, wherein a relief angle of the primary facet is 5° to 40° and a relief angle of the secondary facet is 10° to 40°;
• a progressive transition portion between the pilot and the drill body, the progressive transition portion being at least a double chamfer having a first chamfer portion extending from and behind the pilot and a second chamfer portion extending from and behind the first chamfer portion, the first chamfer having a first chamfer portion angle of 12° to 18° and the second chamfer having a second chamfer portion angle of 5° to 15°;
• and
• at least one flute extending from the drill tip to the drill body, wherein a helix angle of the flute decreases from a start helix angle at the drill tip to a finish helix angle in the drill body.