Annular tool for cutting holes in metal

A tool for cutting an annular hole in a rigid workpiece responsive to rotary motion and force between the tool and the workpiece, comprising in combination:

• a mounting shank, having
• a powering shaft, having first and second end portions with means for interconnection with a holding device, at the first end portion of the mounting shank, and
• a diametrically larger cylindrical shank arbor extending in axial alignment from the second end portion of the mounting shank, said cylindrical shank arbor having means for releasably fastening an annular cutter to the second end portion distal from the powering shaft;
• and
• a circularly annular cutter releasably fastened in axial alignment to the shank arbor and defining a medial channel and a plurality of spirally arrayed alternating similar flutes and similar lands on radially inner and outer surfaces, each of said flutes having
• an inner surface substantially coincident on a common circle concentric with the axis of the annular cutter,
• angulated sides extending outwardly from the inner surface of each flute and away from each other, and
• each land between adjacent flutes defining a cutting tooth at each axially outer end of each land side facing the direction of rotation of the annular cutter, each said cutting tooth being coplanar.

An annular tool for cutting a hole in a metallic workpiece responsive to rotary motion of the tool and force between the tool and the workpiece, comprising in combination:

• a mounting shank, having
• a powering shaft, having first and second end portions with means at the first end portion to releasably and irrotatably interconnect with a powering tool for rotation, and
• a diametrically larger, circularly cylindrical shank arbor carried by the powering shaft to extend in axial alignment from the second end of the powering shaft, said shank arbor having
• an annular fastening groove defined in the second end portion in axial alignment with the powering shaft to receive an end portion of a cylindrical cutter and at least one fastening screw extending in threaded engagement in a hole defined from the external peripheral surface of the shank arbor to the annular fastening groove, and
• a plurality of chip channels extending from the axially inner portion of the fastening groove radially outwardly through the shank arbor to allow the passage of cuttings through the chip channels and radially outwardly from the fastening groove;
• a circularly annular cutter, with end portions perpendicular to its axis, releasably fastened in the fastening groove defined in the shank arbor, said annular cutter defining a plurality of alternating similar flutes and similar lands on radially inner and outer surfaces, said flutes and lands extending in spiral orientation at an angle of up to seventy degrees to the axis of the annular cutter and each of said flutes
• on the radially inner surface of the annular cutter being defined between adjacent flutes on the radially outer surface of the annular cutter,
• on both radially inner and outer surfaces of the annular cutter having inner surfaces coincident on a common circle concentric with the axis of the annular cutter, and
• on both radially inner and outer surfaces of the annular cutter having angulated sides extending outwardly from the inner surface of each flute and away from each other at a smaller included angle to a radial line of the annular cutter extending through the angulated side of between ten and sixty degrees, and
• each of said lands between adjacent flutes
• defining a cutting tooth at each end of each land side facing the direction of rotation of the annular cutter,
• having end surfaces sloping axially inwardly at an angle of between five and thirty degrees, and
• having end surfaces sloping in a circumferential direction away from the forward edge defining a cutting tooth.