Stepped rotary broaches and methods and systems employing same

A stepped rotary broach comprising:

• a support portion configured to allow for the stepped rotary broach to be supported by a toolholder;
• and
• a contact portion integrally formed with or coupled to the support portion,
• wherein the contact portion includes a face and an axially-extending surface, and extends between the face and the support portion, the support portion extending between the contact portion and a distal end of the stepped rotary broach,
• wherein the axially-extending surface includes a first contact surface and a plurality of step formations, wherein each of the step formations extends between the face and a respective location along the axially-extending surface at which the respective step formation adjoins a respective portion of the first contact surface,
• wherein each of the step formations includes respective first and second steps that each include a respective first surface region extending in a respective first direction about a central axis of the stepped rotary broach, and
• wherein the respective first surface regions of the respective first and second steps of the respective step formations are respectively positioned either closer to or farther from the central axis of the stepped rotary broach than are the respective portions of the respective first contact surface that respectively adjoin the respective step formations.

A machining method employing a stepped rotary broach comprising:

• mounting the stepped rotary broach on a toolholder in a manner such that a central axis of the stepped rotary broach is skewed relative to a rotational axis of the toolholder,
• wherein the stepped rotary broach includes a support portion and a contact portion integrally formed with or coupled to the support portion,
• wherein the contact portion includes a face and a periphery, and extends between the face and the support portion, the support portion extending between the contact portion and a distal end of the stepped rotary broach,
• wherein the periphery includes an outer surface and a plurality of step formations, wherein each of the step formations extends between the face and a respective location along the periphery at which the respective step formation adjoins a respective portion of the outer surface,
• wherein each of the step formations includes a respective first step including a respective first surface region extending in a respective first direction about the central axis of the stepped rotary broach, and
• wherein the respective first surface regions of the respective first steps are respectively positioned more closely to the central axis of the stepped rotary broach than are the respective portions of the respective outer surface that respectively adjoin the respective step formations;
• causing the toolholder to be activated so as to rotate the stepped rotary broach about the rotational axis;
• initially moving the toolholder toward a workpiece having a pilot hole until the stepped rotary broach initially contacts the workpiece, the stepped rotary broach experiencing one or more wobbling movements relative to the workpiece due to the central axis being skewed relative to the rotational axis;
• and
• further moving the toolholder toward the workpiece so that the stepped rotary broach proceeds into the pilot hole and the step formations cut away at the workpiece due to the one or more wobbling movements so that the pilot hole is modified to become an enlarged orifice.