I once had to tap some water line holes in hardened (Rc. 56-58) H-13 with a 1/4 pipe tap. Even with a pipe tap reamer two taps per hole was the norm. The best stuff I could find to do this work was called Anchorlube. After I started using the Anchorlube I could get one or two holes per tap. Probably not necessary for regular tapping but great for hard stuff. Mike New
