Step drill
AssigneeBlack & Decker Inc.
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.
Claims19
A step drill bit comprising:
- a cutting head defining a longitudinal axis;
- a point disposed along a leading end of the cutting head and configured to start a hole in a surface to be drilled;
- a first 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;
- a flute disposed between the first cutting edge and the first trailing edge of each of the plurality of steps;
- and
- a negative radial relief provided between the first cutting edge and the first trailing edge in at least two of the plurality of steps of the first land, wherein the negative radial relief increases a radius of the first land between the first cutting edge and the first trailing edge and towards the first trailing edge in the at least two of the plurality of steps.
A step drill bit comprising:
- a cutting head defining a longitudinal axis;
- and
- a plurality of steps, each of the plurality of steps having different effective diameters and comprising:
- a step cutting edge,
- a step trailing edge, and
- a rubbing surface defined by a negative relief formed between the step cutting edge and the step trailing edge on each step;
- and
- a flute extending generally along the longitudinal axis of the cutting head,
- wherein the flute defines the step cutting edge and the step trailing edge for each of the plurality of steps and
- wherein the negative relief increases a radius of each respective step between the step cutting edge and the step trailing edge and towards the step trailing edge on each of the plurality of steps.
A step drill bit comprising:
- a cutting head defining a longitudinal axis;
- a first 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;
- a first trailing edge;
- and
- a positive radial relief extending from adjacent the first cutting edge towards the first trailing edge;
- a flute extending generally along the longitudinal axis of the cutting head, wherein the flute defines the first cutting edge and the first trailing edge for each of the plurality of steps;
- and
- a negative radial relief provided between the positive radial relief and the first trailing edge in at least two of the plurality of steps of the first land, wherein the negative radial relief increases a radius of the first land between the first cutting edge and the first trailing edge and towards the first trailing edge in the at least two of the plurality of steps.
Dependencies are inferred from the claim text.