Those plugs can be quite difficult to remove. BEFORE you round it out & NOW you have to drill & tap. Do yourself a favor. Heat the plug/area up with a GOOD heat gun, propane/map gas or Oxy/Act. It DOES NOT need to be red hot just hot enough to be able to melt some wax, candle wax or whatever, & let it melt around the plug. As the metal cools the wax will wick it's way down the threads & you'll just about be able to remove it with your fingers. Try it, you'll like it & you will have learned something new you may just be able to use in another situation such as this. Tom T.
