To lessen machining allowance at low grinding-efficiency portions on the internal face of a cylinder in the process of honing, without extending the processing time.
In a pneumatic/hydraulic pressure converter unit 29 within a processing head 13, pneumatic pressure is converted into hydraulic pressure, and by a power unit 45, on which the hydraulic pressure works, a transfer unit 57 of an elastic deformation portion 43 shifts to such a direction as to form an orthogonal angle with an axis, jointly with a boring bar 59, which is equipped with a roughing blade 61 and a finishing blade 63. In a state in which hydraulic pressure is applied to the power unit 45 so that the blade 61 is protruded toward the inner face of a cylinder bore 67, the processing head 13 is transferred in an outward movement within the cylinder bore 67, and roughing is thereby carried out. After completion of roughing, application of hydraulic pressure is once lifted, and subsequently, as hydraulic pressure application is resumed and gradually increased, and as the blade 63 is transferred from the inner face of the cylinder bore to the inner-radius direction, the blade is moved through the return course within the cylinder bore 67, and the opening portion on the other side of the cylinder bore is finish-machined into a taper shape. After taper processing, finish machining is implemented, with the hydraulic pressure kept at a constant level.
SUZUKI MASAHISA
TAKASHIMA KAZUHIKO
NISSAN MOTOR