Step drill
AssigneeIrwin Industrial Tool Company
InventorLaVerne R. Durfee
Life of this patent
Estimating the term…
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.
Claims18
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.
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.
Dependencies are inferred from the claim text.