Use a drill press, slow the cut down, and step-drill the hole bigger about 1/32" at a time. Use a good quality lubricant like Rapid Tap or Tap Magic, or plain old 30 weight motor oil if nothing else is available. A can of STP and a pound of unsalted lard makes some of the best general purpose cutting oil available. Mix the STP with the lard until you get a stiff liquid a little thicker than honey that clings to the drill bit when it's applied with a small paint brush. Mix half a cup or so at a time, and your supplies will last a few years. When the chips get hot on a heavy cut, that mix smells like bacon frying.
Jerry
