@John_E , I see you answered your own question. Definitely something like an end mill or a reamer (with a flat rather than conical or bull-nosed end) is preferable. Barring that, take a cheap drill bit of the appropriate diameter and grind off the tip, and then even up and sharpen the end edge of the flutes (DIY end mill for soft materials). I’ve done this for delrin and acrylic. It may work for wood and a soft metal as well (don’t know, this latter assumption is just conjecture).
Anyhoo, I wouldn’t recommend using the abrasive bits for plastic, because they tend to heat the plastic up, make it go gummy and stringy… in the worst case singe/burn.