Abstract: A roller bearing comprising an inner and an outer ring in concentrical arrangement, a series of roller elements being arranged in the space between said rings and being in contact with raceways provided in said rings. The bearing is characterized in that said raceways are provided with parallel grooves, each one of said grooves being arranged in the plane of rotation of said rings and extending along the entire envelope surface, and in mutual correspondence to said inner and outer rings and being arranged for mating interaction with protruding flanges of said roller elements corresponding to said grooves, said protruding flanges extending along the entire envelope surface of said roller elements.

Abstract: The tool-holding spindle assembly, particularly for a grinding machine, comprises means for supporting the shaft of the spindle and a power drive, for example an electric motor for rotating the spindle. The support means comprise at least one electromagnetic radial bearing controlled by a radial detector, having an annular armature mounted on the shaft of the spindle and a fixed armature surrounding this annular armature, an electromagnetic axial bearing having a disc-shaped armature mounted on the shaft of the spindle and a fixed armature, a chain for controlling the radial and/or axial position of the spindle, said chain being connected on the one hand to at least one detector of the radial and/or axial position of the spindle, and on the other hand to excitation coils of the armatures of each magnetic bearing, and means for selectively modifying the signal generated by said at least one position detector.