A cup grinding wheel assembly, comprising: - a support body within which a spindle is rotatably supported around an axis, - a cup grinding wheel having a cup-shaped body with an annular front machining surface wherein passages are formed in the cup-shaped body, leading to the annular front surface of the cup grinding wheel, which can be used to feed coolant into the area of contact between said annular front surface of the cup grinding wheel and the workpiece being machined, said grinding wheel assembly being characterized in that: - at least one circumferential continuous groove is formed in said annular front surface of the cup grinding wheel, extending with a wavy or zig-zag path, so as to be suitable for distributing coolant covering a predominant portion of the radial extension of the aforesaid annular front surface of the cup grinding wheel, - on one end of said spindle a circular disk flange is attached by means of screws, - the cup grinding wheel is attached to said circular disk flange, - the body of the cup grinding wheel has a central disc which is centered over said flange, a cylindrical portion protruding from a front face of the flange being received within a hole of said central disc of the cup grinding wheel body, - the body of the cup grinding wheel further includes a peripheral cylindrical wall extending axially from the disc both in a forward direction, to define said annular front surface, and in the opposite direction, with a wall portion which protrudes axially from the rear face of the central disc, defining a rear circular aperture concentric with the axis of the body of the cup grinding wheel, - the inner surface of said wall portion defines an inner circumferential channel, with a circular profile, designed to define a feed manifold for a coolant to be fed into the area of contact between the abrasive annular front surface of the cup grinding wheel and the workpiece, - said system further comprising at least one coolant dispenser comprising a dispenser body supported in a fixed position by the support body, said dispenser body having a distal portion protruding axially within the body of the cup grinding wheel through the rear circular aperture adjacent to the rear face of the central disc of the grinding wheel body, - within the body of said at least one coolant dispenser, at least one passage is formed having an outlet port facing radially outwards and facing the wall of said inner circumferential channel of the cup grinding wheel. - a support body within which a spindle is rotatably supported around an axis, - a cup grinding wheel having a cup-shaped body with an annular front machining surface wherein passages are formed in the cup-shaped body, leading to the annular front surface of the cup grinding wheel, which can be used to feed coolant into the area of contact between said annular front surface of the cup grinding wheel and the workpiece being machined, - at least one circumferential continuous groove is formed in said annular front surface of the cup grinding wheel, extending with a wavy or zig-zag path, so as to be suitable for distributing coolant covering a predominant portion of the radial extension of the aforesaid annular front surface of the cup grinding wheel, - on one end of said spindle a circular disk flange is attached by means of screws, - the cup grinding wheel is attached to said circular disk flange, - the body of the cup grinding wheel has a central disc which is centered over said flange, a cylindrical portion protruding from a front face of the flange being received within a hole of said central disc of the cup grinding wheel body, - the body of the cup grinding wheel further includes a peripheral cylindrical wall extending axially from the disc both in a forward direction, to define said annular front surface, and in the opposite direction, with a wall portion which protrudes axially from the rear face of the central disc, defining a rear circular aperture concentric with the axis of the body of the cup grinding wheel, - the inner surface of said wall portion defines an inner circumferential channel, with a circular profile, designed to define a feed manifold for a coolant to be fed into the area of contact between the abrasive annular front surface of the cup grinding wheel and the workpiece, - said system further comprising at least one coolant dispenser comprising a dispenser body supported in a fixed position by the support body, said dispenser body having a distal portion protruding axially within the body of the cup grinding wheel through the rear circular aperture adjacent to the rear face of the central disc of the grinding wheel body, - within the body of said at least one coolant dispenser, at least one passage is formed having an outlet port facing radially outwards and facing the wall of said inner circumferential channel of the cup grinding wheel.