A dynamic stiffness simulator which can set reliably both the static and dynamic stiffnesses between wheel and workpiece in wide range was designed. Utilizing this simulator, the effects of the stiffness upon the sparkout time and stability limit of chatter vibration are clarified experimentally. That is, the minimum amount of static stiffness, which is required to give the proper interval of sparkout grinding under the condition as to utilize the specified motor power fully, is experimentally obtained. Secondly, the minimum amount of dynamic stiffness, with particular interest in damping ratio, which is enough to make the operation free from any chatter vibration, is decided experimentally under the above condition. From these test results, the propriety of stiffness determination method developed in the previous paper is evaluated to be practical.