Step drill

Patent metadata

Field	Value
Publication number	US-9687915-B2
Application number	US-201414299163-A
Country	US
Kind code	B2
Filing date	Jun 9, 2014
Priority date	Jun 14, 2013
Publication date	Jun 27, 2017
Grant date	Jun 27, 2017

Abstract

A step drill bit has a cutting head defining a longitudinal axis and having a plurality of steps having different effective diameters. First and second cutting edges are formed in the cutting head. The first cutting edge and the second cutting edge are arranged such that the bit is asymmetric in a plane perpendicular to the longitudinal axis relative to a plane containing the longitudinal axis. A rubbing surface is formed on each step where the rubbing surface extends to approximately the effective diameter of that step such that the first cutting edge, second cutting edge and the rubbing surface forms three points of contact with the side wall of the hole being cut.

First claim

The invention claimed is:

1. A step drill bit comprising:
a cutting head defining a longitudinal axis;
a first flute and a second flute dividing the cutting head into a first land and a second land, each of the first land and the second land comprising a plurality of steps having different effective diameters;
each of the plurality of steps of the first land comprising;
a first cutting edge and a first trailing edge formed in the first land;

each of the plurality of steps in the second land comprising:
a second cutting edge and a second trailing edge formed in the second land;

a negative radial relief provided between at least one of the first cutting edge and the first trailing edge of the first land or the second cutting edge and the second trailing edge of the second land in at least two of the plurality of steps of the first land and the second land, wherein the negative radial relief increases a radius of the first land between the at least one of the first cutting edge and the first trailing edge and towards the first trailing edge or of the second land between the second cutting edge and the second trailing edge and towards the second trailing edge in at least two of the plurality of steps,
wherein the first cutting edge and the second cutting edge are arranged such that the bit is asymmetric in a plane perpendicular to the longitudinal axis relative to a plane containing the longitudinal axis.

2. The step drill bit of claim 1 , wherein the first land and the first flute create the first cutting edge and the second land and the second flute create the second cutting edge.

3. The step drill bit of claim 1 , wherein the first cutting edge and the second cutting edge are disposed at a center angle relative to one another of less than 180 degrees.

4. The step drill bit of claim 1 , wherein the first cutting edge is disposed at a center angle of between approximately 120 and 160 degrees relative to the second cutting edge.

5. The step drill bit of claim 1 , wherein the first cutting edge is disposed at a center angle of approximately 140 degrees relative to the second cutting edge.

6. The step drill bit of claim 1 , wherein the first land extends for a greater center angle than the second land.

7. The step drill bit of claim 6 , wherein the negative radial relief defines a rubbing surface and wherein the first cutting edge, the second cutting edge and the rubbing surface formed on each of the plurality of steps of at least one of the first land and the second land extend to approximately the effective diameter.

8. The step drill bit of claim 7 , wherein the rubbing surface is formed on at least one of the first trailing edge and the second trailing edge of each of the plurality of steps of at least one of the first land and the second land.

9. The step drill bit of claim 1 , wherein the plurality of steps of the first land and the second land are configured to create three points of contact between each of the plurality of steps of the first land and the second land and a side wall of a hole being cut.

10. The step drill bit of claim 1 , wherein the negative radial relief defines a rubbing surface and wherein the first cutting edge, the second cutting edge and the rubbing surface formed on each of the plurality of steps of at least one of the first land and the second land extend to approximately the effective diameter.

11. The step drill bit of claim 1 , wherein each of the plurality of steps of the first land and the second land comprises a positive radial relief extending from the first cutting edge and the second cutting edge a first arc length and each of the plurality of steps of the first land and the second land is formed with an axial relief extending from the first cutting edge and the second cutting edge a second arc length where the first arc length and the second arc length are different.

12. The step drill bit of claim 11 , wherein the first arc length is less than the second arc length.

13. The step drill bit of claim 11 , wherein at least one of the first arc length and the second arc length are different on at least two of the plurality of steps of the first land and the second land.

14. A step drill bit comprising:
a cutting head defining a longitudinal axis; and having a plurality of steps having different effective diameters, each of the plurality of steps comprising a first step cutting edge, a first step trailing edge, a second step cutting edge, and a second step trailing edge and a rubbing surface defined by a negative relief formed between at least one of the first step cutting edge and first step trailing edge or the second step cutting edge and second step trailing edge on each step, wherein the negative relief increases a radius of each respective step between the at least one of the first step cutting edge and the first step trailing edge and towards the first step trailing edge or between the second step cutting edge and the second step trailing edge and towards the second step trailing edge on each of the plurality of steps, and wherein the rubbing surface extends to approximately the effective diameter of that step.

15. The step drill bit of claim 14 , wherein the first step cutting edge is disposed at a center angle of between approximately 120 and 160 degrees relative to the second step cutting edge.

16. The step drill bit of claim 14 , wherein the cutting head comprises two flutes that define a first land and a second land, wherein the first land is larger than the second land, wherein the first step cutting edge is disposed along a first edge of the first land and the first step trailing edge is disposed along a second edge of the first land, wherein the second step cutting edge is disposed along a first edge of the second land and the second step trailing edge is disposed along a second edge of the second land, and wherein the rubbing surface is disposed on the first land.

17. The step drill bit of claim 16 , wherein the rubbing surface is located adjacent the first step trailing edge of the first land.

18. The step drill bit of claim 14 , wherein each of the plurality of steps comprises a positive radial relief extending from the first step cutting edge and the second step cutting edge a first center angle and each of the plurality of steps is formed with an axial relief extending from the first step cutting edge and the second step cutting edge a second center angle where the first center angle and the second center angle are different.

Assignees

• Irwin Ind Tool Co

Inventors

• Durfee Laverne R

Classifications

• B23B51/009 Primary

  Stepped drills · CPC title

• Y10T408/906

  Axially spaced · CPC title

• B23B2251/70

  Drills with vibration suppressing means · CPC title

• B23B2251/282

  Unequal spacing of cutting edges in the circumferential direction · CPC title