A Pretty Small Hole
The holes I want are 0.1mm, 0.15mm and 0.2mm. Of these I only had 0.2mm bits so I had a go with them. Several attempts in steel ended up with broken bits after about 2mm.
An attempt in aluminium was successful though, after I had used up all nmy 0.2mm bits and started into my 0.25mm bits.
I used a gcode program that was generated by a Tcl script, this program slowly drills into the material, with the occasional removal for chip clearance. I think the program is still a bit wrong, as I have broken a lot of bits with it.
Anyway, here's a 0.25mm hole in 2.3mm aluminium:
This is the hole being drilled: