They go even smaller than 0.1mm. McMaster-Carr sells a 0.051mm drill bit for $25: https://www.mcmaster.com/8904A11/ https://www.mcmaster.com/8904A11/ That's th

They go even smaller than 0.1mm. McMaster-Carr sells a 0.051mm drill bit for $25: https://www.mcmaster.com/8904A11/ https://www.mcmaster.com/8904A11/ That's the absolutely small I could find, though I suspect specialty vendors have even smaller ones. You can find MMC's other micro drill bits here: https://www.mcmaster.com/micro-drill-bits/ https://www.mcmaster.com/micro-drill-bits/ My only experience with these was in school where we used 0.25mm micro end mills (like a drill bit that cut sideways) to cut our own PCBs. A small desktop micro CNC would just cut the traces out of a blank copper clad board. That's when I learned how easily these bits can break, so even though they're not that expensive you go through them very quickly.