[CitizenOfDreams]

Though the .8mm ( and especially the .4mm ) look so thin and fragile. It just seems that there's no way they are going to handle 300mm/sec. Have you ever tried a sub-1mm bit?

I only use a 1.8mm chip breaker for routing PCBs. For smaller holes I use drilling (a set of carbide drill bits sized from 0.3mm to 2.0mm).