This Instructable well help you drill a line or grid of holes with 1/400th of an inch (0.06mm) tolerances. Or so. The holes in this photo are 1/32" (0.8mm) across and 3/64" (1.2mm) apart, but the same technique can be used to drill even smaller or closer holes. And you can go bigger too, the same method will use to drill a grid of holes of just about any size.
It's not super difficult, but it does take the right equipment, attention to detail, and practice. I probably drilled 30-40 holes before I got the technique down well enough to get even spacing most of the time.
It's worth noting that this works best on soft material like plastic and wood. Harder materials like steel are a bit tricky since I don't center punch the holes which can cause the drill bit will to wander a bit.
Thanks to my brother Nick for giving me the nudge in the right direction
to figure this one out.