Patent ID: 8795028

Claim:
A spindle for a machine tool, said spindle being rotatable about an axis of rotation and comprising: an outer spindle portion; an inner spindle portion, with each of said outer spindle portion and said inner spindle portion being rotatable about said axis relative to one another; a first plurality of magnets arranged in a ring shape about an inside surface of said outer spindle portion and a second plurality of magnets arranged in a ring shape about an outside surface of said inner spindle portion, said first plurality and said second plurality being the same number, said first plurality of magnets and said second plurality of magnets facing one another, wherein the second plurality of magnets on said inner spindle portion are radially spaced from the first plurality of magnets on said outer spindle portion, said inner spindle portion being movable during operation of said spindle with respect to said outer spindle portion along said axis of rotation, wherein said inner spindle portion is axially movable over a predetermined amount via an inner element axially movable between defined stop positions, wherein said defined stop positions are positioned on one or more inner surfaces of a stationary housing arranged radially outward of said inner element, and wherein at least one of the inner surfaces includes a spring and/or piston for moving said inner element and inner spindle portion.