At the risk of being taken to have admitted to being a klutz, I'll say the the 4-12mm step drill is the best tool for this job, if your goal is to do it accurately, with next to no risk of chipping, while staying centered, not making an oversize hole, and at very low cost in tooling.
There is no advantage to making a 1/2" hole for an 15/32" jack. All that does is unnecessarily introduce play and weakness. 12mm is just a tiny bit more than 15/32". The step drill is single-fluted, which makes it stay perfectly centered in the existing pin hole. The small increments, along with single flute, make it nearly impossible for the bit to chatter or take out a chip. And you can get them cheaply--$6.59 with shipping on Ebay. This one will not be of the same quality is Irwin or Milwaukee, but if you are only going to do a guitar or two they are okay. And you don't need to tape or dowel the existing hole, because you are starting centered with the smaller bit diameters already inside the hole.
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Last edited by Howard Klepper; 04-26-2024 at 12:54 AM.
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