Step drill bit

A step drill bit comprising:

• a shank extending along a bit axis;
• a body having a proximal end adjacent the shank and a distal end opposite the proximal end, the body defining a plurality of axially stacked, progressively sized steps including a first step at the distal end, a terminal step at the proximal end, and a plurality of intermediate steps disposed between the first and terminal steps;
• a flute in the body, the flute defining an elongated groove that extends from the distal end to the proximal end;
• and
• a plurality of cutting edges formed in the body, each cutting edge disposed along one of the plurality of steps, each cutting edge defining a helix angle and a radial rake angle;
• wherein the helix angle of the cutting edge at the terminal step is greater than the helix angle of the cutting edge at the first step;
• wherein the radial rake angle of the cutting edge at the terminal step is greater than the radial rake angle of the cutting edge at the first step;
• and
• wherein the radial rake angle of the cutting edge at each of the plurality of intermediate steps incrementally increases from the first step to the terminal step.

A step drill bit comprising:

• a shank extending along a bit axis;
• a body having a proximal end adjacent the shank and a distal end opposite the proximal end, the body defining a plurality of axially stacked, progressively sized steps including a first step at the distal end, a terminal step at the proximal end, and a plurality of intermediate steps disposed between the first and terminal steps;
• at least one flute in the body, each flute defining an elongated groove that extends from the distal end to the proximal end;
• and
• a plurality of cutting edges formed in the body, each cutting edge disposed along one of the plurality of steps, each cutting edge defining a helix angle and a radial rake angle;
• wherein the helix angle of the cutting edge at the terminal step increases by at least 70 percent relative to the helix angle of the cutting edge at the first step;
• wherein the radial rake angle of the cutting edge at the terminal step increases by at least 40 percent relative to the radial rake angle of the cutting edge at the first step;
• and
• wherein the radial rake angle of the cutting edge at each of the plurality of intermediate steps incrementally increases from the first step to the terminal step.