Abstract: A numerical control apparatus which controls a grinding machine that includes a work table for supporting a workpiece, a grinding wheel and a truing device for truing the grinding wheel. The workpiece has taper and non-taper portions to be ground. The numerical control apparatus includes first and second storage means for storing first and second truing programs which respectively define first and second relative movements between the truing device and the grinding wheel to form a taper grinding surface and a non-taper grinding surface on the grinding wheel. The numerical control apparatus executes the first truing program prior to grinding the taper portion of the workpiece and also executes the second truing program after grinding the taper portion.

Abstract: A method of grinding a rounded annular corner formed between a cylindrical portion of a workpiece and a shoulder portion adjacent to the cylindrical portion, an apex portion of a grinding wheel is first positioned at a starting point to be in contact with a surface of the rounded annular corner and is subsequently moved along the surface of the rounded annular corner from the starting point to a terminal point where the shoulder portion is ground by the grinding wheel. During the movement of the grinding wheel from the starting point to the terminal point, the surface of the rounded annular corner is ground by the apex portion of the grinding wheel. When moved to the terminal point, the apex portion of the grinding wheel is retracted radially outwardly from the terminal point to an escape point where the apex portion is spaced from the outer periphery of the shoulder portion.

Abstract: In a numerical control grinding machine, a workpiece with a taper portion to be ground is rotatably supported on a swivel table which is mounted on a traverse table to be pivotable about a pivot. For grinding the taper portion, the traverse table is moved to bring a reference end surface of a workpiece into engagement with a measuring device, and a numerical controller detects a deviation of the pivot from a corresponding position in the case of a workpiece model. The numerical controller is in advance given a reference table feed amount, a reference swivel pivot angle and a reference wheel feed amount through which the traverse table, the swivel table and the grinding wheel would be moved respectively after the reference end surface is brought into engagement with the measuring device, to precisely grind a corresponding taper portion of the workpiece model if the same were supported on the swivel table.