Use layout die to stain the aluminum. Center punch the center of the hole location. Use a compass with a metal point installed to scribe a circle the size of the gauge hole onto the metal. Center punch all along the scribed circle. Make the punches about 1/4" apart. Drill a series of 3/16 ,or so , holes all around the circumference of the circle. Stay inside the punched line and make the holes almost touch each other. Use a small and sharp chisel to cut between the holes until the center falls out. File to the line with a half round file. Slow but cheap. You can make large holes in frames with this method.
I have to agree on the circle cutter in a drill press. I used one to make the filler hole, 4" I think, in my plastic fuel tank. Caught and darn near broke my hand. Lesson learned, eventhough I knew I should have used a drill press in the first place!
I have Hougen annular hole cutters and they do an incredible job. The only problem with them is if you only have a couple holes to cut they are way to expensive to buy. I agree with the hole saws but they really should be pretty good ones. Easy and fast with a hole saw Rod
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