Method of manufacturing ground product and cup grinding stone

A method of grinding a workpiece having an initial polygonal shape to a final cylindrical shape after grinding, the method comprising the steps of:

• (a) providing a cup grinding stone including a side grinding stone portion provided on a side surface of the cup grinding stone and a bottom grinding stone portion provided on a bottom surface of the cup grinding stone, a boundary between the side grinding stone portion and the bottom grinding stone portion is rounded, and the bottom grinding stone portion is annularly provided along an outer periphery of the bottom surface,
• (b) disposing the cup grinding stone such that a rotational central axis of the cup grinding stone is parallel and offset from a state where the central axis of the cup grinding stone is orthogonal to and intersects a central axis of the workpiece, and the central axis of the cup grinding stone is offset at an offset distance such that an imaginary line segment extends across the bottom grinding stone portion when the central axis of the workpiece is projected onto the bottom grinding stone portion of the cup grinding stone, and such that a length of the imaginary line segment is in a range from Lmax/2 to Lmax, wherein Lmax is the length of the imaginary line segment that extends across the bottom grinding stone portion when the central axis of the cup grinding stone is offset at a tangent offset distance such that the imaginary line segment forms a tangent with an inner periphery surface of the bottom grinding stone portion;
• and
• (c) axially rotating the cup grinding stone offset at the offset distance so that the cup grinding stone grinds an outer peripheral surface of the workpiece while the workpiece is axially rotating in a direction toward the offset direction of the offset distance of the central axis of the cup grinding stone and moving the workpiece in the axial direction of the workpiece, such that the side grinding stone portion rough-grinds the outer peripheral surface of the workpiece and the bottom grinding stone portion finish-grinds the outer peripheral surface of the workpiece to obtain the final cylindrical shape after grinding.