Cutting tool is, needless to say, the major participant in cutting and so we can get much information about the present cutting condition in operation with sensors attached to it. Moreover, we can improve cutting condition by processing tool itself like reforming tool shape, adding some device to it and so on. Water flow in a pipe through tool shank can have such functions as above. One of such functions of it is cooling effect. Examined here is this effect, changing water velocity and water temperature.