It is time to change the SG-250 Grindstone from my Tormek T-7 to exchange it for a new one. I have tried the wrench tap (harder and harder till it is wrench pounding) method described in the literature included with the new Grindstone and have had no success in removing the nut that holds the Grindstone to the shaft. I have made sure that my orientation is the same as shown in the illustration. I have treated it as a right hand thread nut as shown by the illustration in the instructions so that it has to be turned clockwise for removal of the nut. I have removed the Grindstone and shaft from the machine and see no evidence of rust. There is a small amount of a grayish deposit around the circumference of the outside washer inboard of the nut. Does anyone have suggestions on what I am doing wrong and how to get the nut off? I appreciate any help.