I used a Black & Decker variable speed drill & a plain ol' metal drill-bit.Cooling was by dipping the drill-bit in a cap full of engine oil.Fair enough,it took a half-hour to drill the hole out,but that was nothing compared to my first foray into drilling ss with a Dremel-clone & its 22 watt motor...that was 3 hours lying on the floor in agony(my spines fucked)just to enlarge one hole(I wanted two)swearing at the shitty clones feebleness.To drill a completely new hole in my ss caps,I just tape over the cap(cheap rolls of plastic insulation tape)to build a layer of tape,mark the spot I want the hole & start drilling.A little care until the drill-bit has cut into the metal before applying any kind of force & a couple minutes once the hole is completed,with the Dremel+grindstone to remove any burrs & thats it,job done.Then a total scrub/wash/boil in soapy water removes any oil residue & the result is..clouds of vapour without needing a hoover pipe up my butt.