Patent ID: 8550189

Claim:
A chuck assembly for supporting a bit, the bit having a head and a shank connected to the head, a plurality of radially-outwardly extending bit splines being spaced about an outer circumference of a portion of the shank, the chuck assembly comprising: a chuck having a body defining a bore extending along an axis between a first end and a second end, the chuck receiving the shank of the bit through the first end such that the bit is supportable by the chuck, the chuck including a plurality of radially-inwardly extending chuck splines formed in the bore proximate the second end, the chuck splines being spaced about an inner circumference of the bore, adjacent ones of the chuck splines being separated by a groove, a chuck spline maximum inner diameter being defined between grooves on opposite sides of the axis, a first portion of the bore being defined between the chuck splines and the first end, the first portion of the bore having a minimum inner diameter greater than the chuck spline maximum inner diameter, a support ring recess being defined in the bore axially between the chuck splines and the first end; a support ring positionable in the support ring recess, the support ring, when positioned in the support ring recess, having a support surface facing toward the chuck splines and a support ring inner diameter, the support ring inner diameter being less than the minimum inner diameter of the first portion of the bore; and a drive pin positionable circumferentially between one of the chuck splines and an associated one of the bit splines, the drive pin being operable to transmit rotational torque from the one of the chuck splines to the associated one of the bit splines, the drive pin having an axial end surface at least partially engageable with the support surface of the support ring to limit axial movement of the drive pin toward the first end.