Abstract: In a grinding method and apparatus, a machining portion of a workpiece is ground with a grinding wheel on a trial, and shape errors in respective rotational phases of the machining portion are measured after the trial grinding. Based on the shape errors, control data defining workpiece rotational speeds for respective rotational phases of the workpiece is prepared so that the workpiece rotational speed is made to be slow for a rotational phase in which the machining portion is undercut, but to be fast for another rotational phase in which the machining portion is overcut, and the machining portion of the workpiece is ground as the rotational speed of the workpiece is controlled in accordance with the control data.

Abstract: In a coolant supply apparatus for a grinding machine, a wheel unbalance prevention device is operated within the period from the switching to the closed state of a shut-off valve which is provided on a conduit connecting a coolant supply to a coolant nozzle, to the rotation stop of the grinding wheel and prevents the coolant remaining in a part of the conduit on the downstream side of the shut-off valve and in the coolant nozzle, from dropping on the grinding surface of the grinding wheel during the rotation stop of the grinding wheel. Thus, it can be prevented that the coolant locally penetrates into the grinding wheel to put the same out of balance.

Abstract: A bed 10 for machine tool includes a fluid channel 16 crossing the bed 10 and at least one reinforcement 30 bridging the fluid channel 16. Thus the machining accuracy of a workpiece becomes higher.

Abstract: In a grinding method and apparatus, a machining portion of a workpiece is ground with a grinding wheel on a trial, and shape errors in respective rotational phases of the machining portion are measured after the trial grinding. Based on the shape errors, control data defining workpiece rotational speeds for respective rotational phases of the workpiece is prepared so that the workpiece rotational speed is made to be slow for a rotational phase in which the machining portion is undercut, but to be fast for another rotational phase in which the machining portion is overcut, and the machining portion of the workpiece is ground as the rotational speed of the workpiece is controlled in accordance with the control data.

Abstract: A workpiece W and a grinding wheel G are relatively moved in Z and X-axis directions perpendicular to each other, the rotational axis of the grinding wheel is inclined relative to the X-axis, and the grinding wheel is composed of a taper section Ga having a generating line parallel to the Z-axis and a spherical section Gb connecting with the generating line at the maximum diameter portion of the taper section Ga. While performing a cam profile generating motion, the grinding wheel is controlled to perform a plunge grinding feed toward the workpiece in the X-axis direction to effect a plunge grinding on the cam of the workpiece and then, while performing the cam profile generating motion, is controlled to perform a traverse grinding feed in the Z-axis direction to effect a traverse grinding on the cam.

Abstract: A method for measuring the diameter and eccentricity of a crankpin of a crankshaft which is ground on a grinding machine. A reference plate is provided on a headstock, which is disposed on a table to support the crankshaft. A measurement apparatus having a probe is disposed on a wheel head. Through movements of the table and the wheel head, the probe is first brought into contact with a reference surface of the reference plate, and is then brought into contact with the outer circumferential surface of the crankpin at outermost and innermost points. The distances between the reference surface and the outermost and innermost points are measured, and the diameter and eccentricity of the crankpin are calculated on the basis of the measured distances and the position of the reference surface.

Abstract: On a grinding machine, a workpiece having eccentric cylindrical portions is rotated around the work spindle axis so that the eccentric cylindrical portions effects a planetary motion. A grinding wheel is reciprocated toward and away from the work spindle axis in synchronism with the planetary motion and is also fed toward the work spindle axis to grind the eccentric cylindrical portion into a target cylindrical profile. Upon completion of a part of the grinding operation, the eccentric cylindrical portion under machining is indexed to a predetermined angular position. A diameter measuring device is moved from its rest position to a measuring position to measure the diameter of the eccentric cylindrical portion.

Abstract: On a grinding machine, a workpiece having eccentric cylindrical portions is rotated around the work spindle axis so that the eccentric cylindrical portions effects a planetary motion. A grinding wheel is reciprocated toward and away from the work spindle axis in synchronism with the planetary motion and is also fed toward the work spindle axis to grind the eccentric cylindrical portion into a target cylindrical profile. Upon completion of a part of the grinding operation, the eccentric cylindrical portion under machining is indexed to a predetermined angular position. A diameter measuring device is moved from its rest position to a measuring position to measure the diameter of the eccentric cylindrical portion.

Abstract: A machining apparatus simultaneously machining at least two portions of one workpiece is disclosed. The machining apparatus includes a worktable unit for rotatably driving workpiece, at least two tool heads each of which supports a tool and moves forward to or away from the workpiece, at least two gauging units measuring a diameter of each portion, and control unit controlling motion of each wheel head individually. The control unit controls motions of the wheel heads in according to signals provided from the gauging units, wherein controls all of tool heads to execute a finish grinding process, controls one tool head corresponding to one portion whose diameter became a required value to back off, and controls all of tool heads to execute a spark-out process after diameters of all of the portions became each required value. Therefore, it can prevent that accuracy of one portion machined by one tool head is deteriorated by effect of machining by another wheel head.

Abstract: A method for measuring the diameter and eccentricity of a crankpin of a crankshaft which is ground on a grinding machine. A reference plate is provided on a headstock, which is disposed on a table to support the crankshaft. A measurement apparatus having a probe is disposed on a wheel head. Through movements of the table and the wheel head, the probe is first brought into contact with a reference surface of the reference plate, and is then brought into contact with the outer circumferential surface of the crankpin at outermost and innermost points. The distances between the reference surface and the outermost and innermost points are measured, and the diameter and eccentricity of the crankpin are calculated on the basis of the measured distances and the position of the reference surface.

Abstract: A grinding machine includes a spindle head for rotatably driving a crankshaft around a journal center as a rotational axis and, two wheel heads that support respective two grinding wheels and that advance and retract in a direction perpendicular to the rotational axis independently with each other. Two of plural pin portions of the rotating crankshaft are simultaneously ground by the respective two grinding wheels, in which rotational phases of the two pin portions are different from each other. Further, the rotational phases of the two pin portions are stored as a combination in a memory. The two pin portions are simultaneously ground in accordance with the combination by the respective two grinding wheels.

Abstract: A grinding wheel is for use in a grinding machine, and is attached on a wheel spindle of the grinding machine for simultaneously grinding at least two parts of a workpiece. The grinding wheel includes at least two wheel cores. Each of wheel cores has a disk-like shape. An abrasive layer is disposed on a circumferential surface of each of the wheel cores. A spacer portion is inseparably fixed on at least one of the wheel cores for keeping a space between the abrasive layers of the wheel cores. And a first labyrinth portion located on one of side surfaces of one of the wheel cores for forming a labyrinth seal with a second labyrinth portion arranged on the grinding machine. The number of separable parts of the grinding wheel are extremely decreased in consideration of imbalance of every part. The spacer portion is integral with at least one of the wheel cores.

Abstract: A wheel-head feed mechanism for a grinder comprising a base and a wheel head which is guided by a linear guide section provided on the base and rotatably supports a grinding wheel via a wheel spindle driven by a motor. The wheel-head feed mechanism includes feed screw mechanism composed of a screw shaft and a nut unit engaged with the screw shaft, the feed screw mechanism advancing and retracting the wheel head with respect to a workpiece, and servomotor for rotating one of the screw shaft and the nut unit. The screw shaft is offset from the linear guide section toward the wheel spindle. The nut unit includes a radial hydrostatic bearing section for supporting the root of a male thread of the screw shaft in the radial direction of the screw shaft by hydrostatic pressure, as well as a thrust hydrostatic bearing section for supporting the flanks of the male thread of the screw shaft in the axial direction of the screw shaft by hydrostatic pressure.

Abstract: A feed screw mechanism includes a nut having a female thread, and a feed screw shaft having a male thread screw-engaged with the female thread. A thrust pocket is formed along a flank of the female thread of the nut, and pressurized fluid is supplied thereto. A plurality of separated radial pockets are formed on the crest surface of the female thread of the nut, and pressurized fluid is supplied thereto. The thrust pocket is a continuous spiral groove formed along the flank of the female thread of the nut. This structure provides sufficient rigidity in both the radial and thrust directions while reducing the size of the feed screw mechanism.