Make dang sure you are center when drilling, or she will be off balance, and vibrate like a siv, or WORSE!
If that area is not flat enough to mark with a punch, VERY GENTLY, grind it down smooth with a rasp, or grinder. Use oil when drilling, and drill slowly, so heat does not build up in that area ( very important ) heat may cause metal fatigue.
Star out with a very small bit, and work your way up, less heat, less work, and the bits stay sharper! Also, as you increase bit size, decrease RPM when drilling. Good luck, Stiemmy.
Edited by stiemmy, June 24, 2014 - 08:21 PM.