Abstract: A method of the invention detects a machining load acting on a tool during a machining process, estimates abrasion amount of the tool based on the machining load and a tool abrasion characteristic registered in advance in a memory, and changes automatically tool position compensation amount based on the tool abrasion. The estimating computation of tool abrasion amount is performed by, for example, obtaining in advance a tool abrasion coefficient based on tool abrasion amount per unit time when a main spindle load current value is taken as a reference machining current value, and integrating for a machining time the product of a ratio of a main spindle load current value during an actual machining process to the reference current value and said tool abrasion coefficient.

Abstract: In a position control system, the positional deviation between the position of the control point of the controlled object and the target position is corrected in accordance with the change of the relative positional relationship between mechanically related control axes. The control axes include a main shaft stand and a main shaft. The main shaft stand is supported by a column so that it can move in a vertical direction and is driven by the rotation of a screw shaft. The main shaft is provided on the main shaft stand so that the main shaft stand can move in a horizontal direction. The positional deviation of the main shaft from the target position in the vertical direction is calculated in accordance with the horizontal position of the main shaft with respect to the main shaft stand at the time of the position control. The position of the main shaft from the target position in the vertical direction is corrected based on the positional deviation.

Abstract: A tool T is mounted to the tip of the rotatable main shaft S, and at least the rotation angle of the main shaft S is controlled so that the edge of the tool T is always maintained at the right angle against the direction of the tool movement on the machining program locus, when a work W is machined with the edge T.sub.A of the tool T in the state that the edge T.sub.A of the tool T is offset from the rotation center S.sub.0 of the main shaft S.

Abstract: Disclosed is an NC machine tool apparatus including an NC machine having at least one spindle to which a tool or a sensing device is attached, and a drive mechanism for driving the spindle, and a control unit for driving the spindle through the drive mechanism. The control unit is provided with an NC work program producing means for measuring a machining locus of a workpiece held in the NC machine by the sensing device attached to the spindle in accordance with a source work program which defines a measurement of the machining locus of the workpiece and a method of producing an NC work program, and producing the NC work program on the basis of the measured data and the source work program.

Abstract: A complete-circle operation of a machine tool controlled by an NC-device. Even if the NC-device gives operation commands for respective shafts of the machine tool on the basis of a control locus which is to be a complete circle, the actual operation locus of the machine tool is not a complete circle because the machine tool generates errors due to various causes such as thermal deformation, machine accuracy, etc. If the errors are corrected individually to improve the accuracy, the complexity of the processing cannot be avoided. It is assumed that the operation locus of the machine tool which is controlled for a complete circle becomes an ellipse due to errors involved. A simple process corrects the ellipse such that it is converted to a complete circle.