Can tools be diamond coated a second time?
sp3 does not coat tools that have already had a diamond coating for two reasons. The first is that the diamond deposition process alters the carbide at the surface, and the required surface preparation will be less predictable a second time. The second reason is the uncertainty of the integrity of the ground edges. Often a tool is run until the diamond film is worn through in one or more spots. The carbide substrate will wear very quickly once the diamond is gone, leaving a notch or groove in one or more spots on the tool. These defects are difficult or impossible to remove with further grinding.
