Okuma Corporation

Okuma Machinery Works Ltd.

Takashi Nishimoto

Fumitoshi Terasaki

Yoshiichi Ichikawa

Kazuhisa Niwa

Takeo Shirakura

A tailstock control device supports an object to be machined by driving and controlling a servo motor which drives a driving system of a tailstock having a spring member in forward and backward directions, to cause a tailstock center connected to the tailstock to contact a center hole of the object to be machined. The tailstock control device comprises a limit torque value calculating unit which calculates, as a limit torque value (Tm), a drive torque value of the servo motor necessary for supporting the object to be machined, and a servo control unit which drives and controls the servo motor to attempt to move the tailstock at a tailstock movement velocity (Vs) which is set in advance, until an output torque value (Tr) of the servo motor reaches the limit torque value (Tm). The limit torque value (Tm) is calculated by subtracting, from the support thrust (Fa) necessary for supporting the object to be machined, an excessive thrust Fs which is calculated based on the tailstock movement velocity (Vs).

Tailstock control device

The present invention provides a method of machining a female screw groove in a workpiece whereby the spindle of an internal grinding wheel for machining the workpiece into a female screw is tilted relative to the screw's axis at an angle (&xgr;) smaller than the lead angle (&agr;) of the female screw. First, specifications of the female screw, data on the configuration of the thread groove, and the tilt angle are supplied to a program for calculating data on dressing of the grinding wheel wherein the locus of the groove on cross-sections normal to the axis of the grinding wheel and wheel dressing data are calculated. Second, the grinding wheel on the aforementioned spindle is shaped or dressed by simultaneous triaxial control of the rotation of the single point dresser about a b-axis, and the feed of the grinding wheel table along a z-axis and a cross slide along an x-axis based on the foregoing data. Thereupon, the female screw is machined with the dressed grinding wheel.

Method of machining a female screw and dressing a grinding wheel for female screw machining

A method of machining a member included a screw-shaped portion which is used when the member is ground at the screw-shaped portion by means of a machine tool, in particular, a grinder. A configuration of the tool that projects corresponding to the thread-groove configuration on a section normal to the axis of the screw-shaped portion to be machined is prepared. The axis of the tool is positioned in parallel with the axis of the screw-shaped portion to be machined, and the relevent surface of the screw-shaped portion is machined by moving the tool relative to the screw-shaped portion while their axes are being kept in parallel with each other. According to the present invention, the lead of a small-diameter, deep-grooved female screw-shaped portion may be able to be machined. In addition, an ordinary NC machine tool can be used to machine leads of screw-shaped portions simply by making changes in the NC program.

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Aichi, Japan

Takashi Nishimoto