Grinding method for grinding a workpiece using a grinding wheel

A grinding method for grinding a workpiece using a grinding wheel that has a grinding layer on an outer periphery of a core of the grinding wheel, comprising:

• recording an outside diameter of the core, a first thickness that is a thickness of the grinding layer and a first time difference that is a time difference in arrival at an ultrasonic sensor between a reflected wave from a surface of the grinding layer having the first thickness and a reflected wave from a surface of the outer periphery of the core;
• recording a second time difference that is a time difference in arrival at the ultrasonic sensor between a reflected wave from a surface of the grinding layer having a second thickness that is a thickness of the grinding layer and a reflected wave from the surface of the outer periphery of the core;
• calculating a decrease in time difference, which is a difference between the first time difference and the second time difference;
• calculating a predetermined reduction amount by a product of a component sonic velocity, which is a sonic velocity in a component that constitutes the grinding layer, and the decrease in time difference;
• calculating the second thickness by subtracting the predetermined reduction amount from the first thickness;
• calculating an outside diameter of the grinding wheel based on a sum of double the second thickness and the outside diameter of the core;
• and
• controlling a grinding operation of the workpiece and a truing operation of the grinding wheel on the basis of the calculated outside diameter of the grinding wheel.