A step drill bit includes a shank and a body having a proximal end adjacent the shank and a distal end opposite the proximal end. The body defines a plurality of axially stacked, progressively sized steps including a first step at the distal end, a terminal step at the proximal end, and a plurality of intermediate steps having incrementally increasing diameters disposed between the first and terminal steps. The step drill bit also includes a plurality of cutting edges each disposed along one of the plurality of steps. Each edge defines a helix angle and a radial rake angle. The radial rake angle and the helix angle of the cutting edge at the terminal step is greater than the radial rake angle and the helix angle of the cutting edge at the first step.

A step drill bit includes a shank and a body having a proximal end adjacent the shank and a distal end opposite the proximal end. The body defines a plurality of axially stacked, progressively sized steps including a first step at the distal end, a terminal step at the proximal end, and a plurality of intermediate steps having incrementally increasing diameters disposed between the first and terminal steps. The step drill bit also includes a plurality of cutting edges each disposed along one of the plurality of steps. Each edge defines a helix angle and a radial rake angle. The radial rake angle and the helix angle of the cutting edge at the terminal step is greater than the radial rake angle and the helix angle of the cutting edge at the first step.

A rotary cutting tool includes a tool body including a chip flute portion having a plurality of helical chip flutes separated by lobes. In one aspect, a tunable vibration absorber assembly is disposed within a cavity formed in the chip flute portion. In another aspect, the tunable vibration absorber assembly is disposed within a cavity of a replaceable cutting head. In each aspect, the tunable vibration absorber assembly includes at least two tunable absorber masses, a resilient material between the one or more absorber masses and the cavity, and one or more connecting members for preventing relative angular displacement of the one or more tunable absorber masses. The at least two tunable absorber masses are suspended only by the resilient material, thereby enabling the tunable vibration absorber assembly to be tuned to a desired frequency for suppressing torsional vibration of the rotary cutting tool during a cutting operation.

A rotary cutting tool includes a tool body including a chip flute portion having a plurality of helical chip flutes separated by lobes. In one aspect, a tunable vibration absorber assembly is disposed within a cavity formed in the chip flute portion. In another aspect, the tunable vibration absorber assembly is disposed within a cavity of a replaceable cutting head. In each aspect, the tunable vibration absorber assembly includes at least two tunable absorber masses, a resilient material between the one or more absorber masses and the cavity, and one or more connecting members for preventing relative angular displacement of the one or more tunable absorber masses. The at least two tunable absorber masses are suspended only by the resilient material, thereby enabling the tunable vibration absorber assembly to be tuned to a desired frequency for suppressing torsional vibration of the rotary cutting tool during a cutting operation.

When forming a first preliminary flute on a PCD layer of a columnar body, electrical discharge machining is performed by setting the electrode orientation so that the first twist angle is α. Next, when forming a second preliminary flute on a substrate of the columnar body and a round bar, the grinding process is performed by setting the grinding orientation and direction for a diamond whetstone so that a second twist angle is larger than the first twist angle.

When forming a first preliminary flute on a PCD layer of a columnar body, electrical discharge machining is performed by setting the electrode orientation so that the first twist angle is α. Next, when forming a second preliminary flute on a substrate of the columnar body and a round bar, the grinding process is performed by setting the grinding orientation and direction for a diamond whetstone so that a second twist angle is larger than the first twist angle.

A rotary cutting tool with enhanced bump-off capability is disclosed. The cutting tool includes a tool shank having a pocket. A replaceable cutting head is at least partially disposed within the pocket of the tool shank with an interference fit. A coupling pin assembly is at least partially received within a bore of the tool shank. The coupling pin assembly comprises a sleeve member and a coupling pin at least partially disposed within the sleeve member. The sleeve member includes an upper portion and a lower portion having a non-circular cross-sectional shape with a bump-off surface. An actuation screw contacts the coupling pin assembly and causes the replaceable cutting head to move relative to the tool shank. The bump-off surface of the lower portion of the sleeve member extends radially outward with respect to the coupling pin by a distance, D, thereby providing enhanced bump-off capability.

A rotary cutting tool with enhanced bump-off capability is disclosed. The cutting tool includes a tool shank having a pocket. A replaceable cutting head is at least partially disposed within the pocket of the tool shank with an interference fit. A coupling pin assembly is at least partially received within a bore of the tool shank. The coupling pin assembly comprises a sleeve member and a coupling pin at least partially disposed within the sleeve member. The sleeve member includes an upper portion and a lower portion having a non-circular cross-sectional shape with a bump-off surface. An actuation screw contacts the coupling pin assembly and causes the replaceable cutting head to move relative to the tool shank. The bump-off surface of the lower portion of the sleeve member extends radially outward with respect to the coupling pin by a distance, D, thereby providing enhanced bump-off capability.

Methods and apparatus for forming an aperture in a composite component are provided. For example, a method for forming an aperture in a ceramic matrix composite (CMC) component comprises, based on a final dimension of the aperture, selecting a tool having a tool size and a cutting surface; selecting an angle at which to cut the component with the tool; cutting a back surface of the component with the tool, the cutting surface positioned at the angle; repositioning the tool relative to the component; and cutting the aperture through to its final dimension. The tool may be a core drill with a diameter within a range of 60% to 90% of the aperture final dimension. The angle may be within a range of 10° to 60° with respect to the back surface. The aperture may be cut through to its final dimension from a front surface of the component.

Methods and apparatus for forming an aperture in a composite component are provided. For example, a method for forming an aperture in a ceramic matrix composite (CMC) component comprises, based on a final dimension of the aperture, selecting a tool having a tool size and a cutting surface; selecting an angle at which to cut the component with the tool; cutting a back surface of the component with the tool, the cutting surface positioned at the angle; repositioning the tool relative to the component; and cutting the aperture through to its final dimension. The tool may be a core drill with a diameter within a range of 60% to 90% of the aperture final dimension. The angle may be within a range of 10° to 60° with respect to the back surface. The aperture may be cut through to its final dimension from a front surface of the component.