Step drill bit
A drill bit includes a shank, a transition portion, and a body portion defining a plurality of axially stacked, progressively sized steps. The steps include a first step and a terminal step coupled to the transition portion. The first step defines two tip flutes each disposed at a tip flute angle. The body portion defines two body flutes each extending from the first step to the transition portion and disposed at a body flute angle different from the tip flute angle. The drill bit includes a bit tip disposed at the distal end of the body portion and having a chisel edge, a first chisel surface on one side of the chisel edge, and a second chisel surface on an opposite side of the chisel edge. The first chisel surface defines a first relief angle. The second chisel surface defines a second relief angle different from the first relief angle.
1. A drill bit comprising:
a shank extending along a bit axis;
a transition portion coupled to the shank;
a body portion having a distal end and defining a plurality of axially stacked, progressively sized steps including a first step at the distal end and a terminal step coupled to the transition portion, the first step defining two tip flutes each disposed at a tip flute angle from the bit axis, the body portion further defining two body flutes each extending from the first step to the transition portion and disposed at a body flute angle different from the tip flute angle; and
a bit tip disposed at the distal end of the body portion and having a chisel edge intersecting the bit axis, a first chisel surface being on one side of the chisel edge, and a second chisel surface being on an opposite side of the chisel edge, the first chisel surface defining a first relief angle, and the second chisel surface defining a second relief angle that is different from the first relief angle;
wherein each tip flute extends to the first chisel surface or the second chisel surface to define at least part of an edge of the first chisel surface or the second chisel surface;
wherein the body flute angle of each body flute is formed as a compound angle defined by a first body flute angle and a second body flute angle, where the first body flute angle is measured between a centerline of each body flute and the bit axis in a first plane, and the second body flute angle is measured between the centerline of each body flute and the bit axis in a second plane that is orthogonal to the first plane;
wherein the first body flute angle is between approximately 4.5 degrees and approximately 5.5 degrees, and wherein the second body flute angle is between approximately 1 degree and approximately 3 degrees.
2. The drill bit of claim 1 , wherein the second relief angle is approximately twice as large as the first relief angle.
3. The drill bit of claim 1 , wherein the first relief angle is between approximately 10 degrees and approximately 20 degrees with respect to a reference axis that is perpendicular to the bit axis, and wherein the second relief angle is between approximately 25 degrees and approximately 35 degrees with respect to the reference axis.
4. The drill bit of claim 1 , wherein each tip flute has a u-shaped cross section as viewed along the bit axis.
5. The drill bit of claim 4 , wherein each tip flute extends through approximately a quarter-circle.
6. The drill bit of claim 1 , wherein the tip flute angle of each tip flute is formed as a compound angle defined by a first tip flute angle and a second tip flute angle, where the first tip flute angle is measured between a centerline of each tip flute and the bit axis in a first plane, and the second tip flute angle is measured between the centerline of each tip flute and the bit axis in a second plane that is orthogonal to the first plane.
7. The drill bit of claim 1 , wherein the bit tip has a primary tip angle measured through the bit axis from the first chisel surface to the second chisel surface that is between approximately 130 degrees and approximately 140 degrees.
8. A drill bit comprising:
a shank extending along a bit axis;
a transition portion coupled to the shank;
a body portion having a distal end and defining a plurality of axially stacked, progressively sized steps including a first step at the distal end and a terminal step coupled to the transition portion, the first step defining two tip flutes each disposed at a tip flute angle from the bit axis, the body portion further defining two body flutes each extending from the first step to the transition portion and disposed at a body flute angle different from the tip flute angle; and
a bit tip disposed at the distal end of the body portion and having a chisel edge intersecting the bit axis, a first chisel surface being on one side of the chisel edge, and a second chisel surface being on an opposite side of the chisel edge, the first chisel surface defining a first relief angle, and the second chisel surface defining a second relief angle that is different from the first relief angle;
wherein each tip flute extends to the first chisel surface or the second chisel surface to define at least part of an edge of the first chisel surface or the second chisel surface;
wherein the tip flute angle of each tip flute is formed as a compound angle defined by a first tip flute angle and a second tip flute angle, where the first tip flute angle is measured between a centerline of each tip flute and the bit axis in a first plane, and the second tip flute angle is measured between the centerline of each tip flute and the bit axis in a second plane that is orthogonal to the first plane;
wherein the first tip flute angle is between approximately 36 degrees and approximately 46 degrees, and wherein the second flute tip angle is between approximately 10 degrees and approximately 20 degrees.
9. The drill bit of claim 8 , wherein the second relief angle is approximately twice as large as the first relief angle.
10. The drill bit of claim 8 , wherein the first relief angle is between approximately 10 degrees and approximately 20 degrees with respect to a reference axis that is perpendicular to the bit axis, and wherein the second relief angle is between approximately 25 degrees and approximately 35 degrees with respect to the reference axis.
11. The drill bit of claim 8 , wherein each tip flute has a u-shaped cross section as viewed along the bit axis.
12. The drill bit of claim 11 , wherein each tip flute extends through approximately a quarter-circle.
13. The drill bit of claim 8 , wherein the bit tip has a primary tip angle measured through the bit axis from the first chisel surface to the second chisel surface that is between approximately 130 degrees and approximately 140 degrees.
14. A drill bit comprising:
a shank extending along a bit axis;
a transition portion coupled to the shank;
a body portion having a distal end and defining a plurality of axially stacked, progressively sized steps including a first step at the distal end and a terminal step coupled to the transition portion, the first step defining two tip flutes each disposed at a tip flute angle from the bit axis, the body portion further defining two body flutes each extending from the first step to the transition portion and disposed at a body flute angle different from the tip flute angle; and
a bit tip disposed at the distal end of the body portion and having a chisel edge intersecting the bit axis, a first chisel surface being on one side of the chisel edge, and a second chisel surface being on an opposite side of the chisel edge, the first chisel surface defining a first relief angle, and the second chisel surface defining a second relief angle that is different from the first relief angle;
wherein each tip flute extends to the first chisel surface or the second chisel surface to define at least part of an edge of the first chisel surface or the second chisel surface;
wherein the tip flute angle of each tip flute is formed as a compound angle defined by a first tip flute angle and a second tip flute angle, where the first tip flute angle is measured between a centerline of each tip flute and the bit axis in a first plane, and the second tip flute angle is measured between the centerline of each tip flute and the bit axis in a second plane that is orthogonal to the first plane;
wherein the first tip flute angle is between approximately 54 degrees and approximately 64 degrees, and wherein the second tip flute angle is between approximately 10 degrees and approximately 20 degrees.
15. The drill bit of claim 14 , wherein the second relief angle is approximately twice as large as the first relief angle.
16. The drill bit of claim 14 , wherein the first relief angle is between approximately 10 degrees and approximately 20 degrees with respect to a reference axis that is perpendicular to the bit axis, and wherein the second relief angle is between approximately 25 degrees and approximately 35 degrees with respect to the reference axis.
17. The drill bit of claim 14 , wherein each tip flute has a u-shaped cross section as viewed along the bit axis.
18. The drill bit of claim 17 , wherein each tip flute extends through approximately a quarter-circle.
19. The drill bit of claim 14 , wherein the bit tip has a primary tip angle measured through the bit axis from the first chisel surface to the second chisel surface that is between approximately 130 degrees and approximately 140 degrees.