SPINDLE DEVICE FOR MACHINE TOOL

PROBLEM TO BE SOLVED: To provide a spindle device for a machine tool capable of obtaining a spindle characteristic that satisfies all of various types of machining.SOLUTION: Information regarding various types of machining is stored in an NC program, so that a preload mount applied to a rolling bearing can be controlled so as to be able to obtain the spindle characteristic satisfying all of the various types of machining by controlling a preload applying means based on the NC program. Thus, highly accurate machining is made possible. When a preload command value falls out of a preload range which is the controllable preload area, it can be compensated so as to fall within the preload range. In other words, the preload actually controlled is regulated within the range of preset predetermined preload so that rigidity of the rolling bearing is secured, and heat generation and rising of excess surface pressure of the rolling bearing can be prevented.