A custom attachment for a milling machine enables drilling with 0.1 mm drill bits — a task nearly impossible with standard equipment due to runout tolerances approaching half the bit's diameter. The mechanism uses a collet-driven secondary spindle, a runout-compensating chuck, a lever with counterweight for low-force control, and a dial indicator for depth feedback. Most parts are machined from steel or brass, with a titanium handle for reduced weight. After resolving a runout issue traced to a damaged collet locating pin, the device successfully drilled a 0.1 mm hole 1.8 mm deep and six 0.1 mm holes in the end of a thin steel wire — with imperfections only visible under a scanning electron microscope.
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