My tungsten carbide drill bit wears out on the metal. No chips are collected. I heard that the metal is at least case hardened. So I am pondering weather to buy one of those diamond hole saw/bit. I am trying to finish the zerk fitting installation that was never there. Do these diamond hole bits work ? I am told I have to keep it flushing water to take out the loose metal at the same time while drilling. I just don't know. I do not want to waste money and time if it is not going to work. Any input would be great. This is a vertical down application.