Method and apparatus for forming grooves on a workpiece and for dressing a grindstone used in the groove formation

A method for dressing a grindstone used in a grinding apparatus by means of a rotary dresser having a dress groove, comprising:

• a first positioning process for relatively moving the grindstone in a first direction along the axis of the rotary dresser from a position in which the grindstone faces an inner surface of the dress groove, detecting a contact position reached the moment the grindstone touches one side edge of the dress groove, and stopping the movement;
• a second positioning process for moving the grindstone for a given distance in a second direction along the axis, the second positioning process directly following the first positioning process;
• and
• a dressing process for moving the grindstone toward the inner surface of the dress groove in a direction perpendicular to the axis, thereby bringing a distal end portion of the grindstone into contact with the inner surface of the dress groove, the dressing process directly following the second positioning process.