A mandrel assembly comprising: an elongated mandrel shaft having a longitudinal axis, a proximal end structured to be coupled to a mandrel carrier, and a distal end; a hollow, elongated mandrel structured to be rotatably disposed about said mandrel shaft and structured to concentrically rotate about said mandrel shaft longitudinal axis; a bearing assembly disposed between said mandrel and said mandrel shaft at a single location adjacent said distal end of said mandrel shaft, whereby said bearing assembly rotatably couples said mandrel to said mandrel shaft and is the only coupling between said mandrel and said mandrel shaft; said bearing assembly including at least one ball bearing unit with an outer race, an inner race, and a plurality of ball bearings; said outer race being a torus-shaped body having an outer surface coupled to the mandrel and an inner surface including a bearing race which is an outer race groove of arcuate cross-sectional shape having a proximal edge and a distal edge and where the curvature of the outer race groove substantially corresponds with the curvature or radius of the ball bearings; said inner race being a torus-shaped body having an inner surface coupled to the mandrel shaft and an outer surface including a bearing race which is an inner race groove of arcuate cross-sectional shape having a proximal edge and a distal edge and where the curvature of the inner race groove substantially corresponds with the curvature or radius of the ball bearings; said inner race being disposed within said outer race and with each center substantially aligned, such that a gap is defined between the inner race outer surface and the outer race inner surface; said outer race groove and said inner race groove defining a passage that said ball bearings are disposed within, said passage being oversized to have a greater radial spacing than the diameter of the ball bearings; said ball bearing unit defining a virtual pivot point about which said mandrel pivots relative to said mandrel shaft, said virtual pivot point being disposed substantially on said mandrel shaft longitudinal axis and substantially at the center of the outer race and the inner race. an elongated mandrel shaft having a longitudinal axis, a proximal end structured to be coupled to a mandrel carrier, and a distal end; a hollow, elongated mandrel structured to be rotatably disposed about said mandrel shaft and structured to concentrically rotate about said mandrel shaft longitudinal axis; a bearing assembly disposed between said mandrel and said mandrel shaft at a single location adjacent said distal end of said mandrel shaft, whereby said bearing assembly rotatably couples said mandrel to said mandrel shaft and is the only coupling between said mandrel and said mandrel shaft; said bearing assembly including at least one ball bearing unit with an outer race, an inner race, and a plurality of ball bearings; said outer race being a torus-shaped body having an outer surface coupled to the mandrel and an inner surface including a bearing race which is an outer race groove of arcuate cross-sectional shape having a proximal edge and a distal edge and where the curvature of the outer race groove substantially corresponds with the curvature or radius of the ball bearings; said inner race being a torus-shaped body having an inner surface coupled to the mandrel shaft and an outer surface including a bearing race which is an inner race groove of arcuate cross-sectional shape having a proximal edge and a distal edge and where the curvature of the inner race groove substantially corresponds with the curvature or radius of the ball bearings; said inner race being disposed within said outer race and with each center substantially aligned, such that a gap is defined between the inner race outer surface and the outer race inner surface; said outer race groove and said inner race groove defining a passage that said ball bearings are disposed within, said passage being oversized to have a greater radial spacing than the diameter of the ball bearings; said ball bearing unit defining a virtual pivot point about which said mandrel pivots relative to said mandrel shaft, said virtual pivot point being disposed substantially on said mandrel shaft longitudinal axis and substantially at the center of the outer race and the inner race.