Tiny deep holes in fidget parts are one of those jobs that looks simple until the bits start snapping. The maker needed very small holes, 5mm deep, in fidget parts, and the part had to be finished that same day. To make it harder, three drills had already broken in a single night before this run.
The setup is a CNC milling machine with a high-speed spindle. The metal workpiece sits in a precision vise mounted to an aluminum tooling plate, and a flexible segmented nozzle for coolant or air sits right near the cutting zone. Each hole is opened with a 1/16 end mill before the 1.6mm carbide drill goes in. One detail I find clever is the operation order: the drill cycle comes after the other cutting because of a tool length limitation with the end mill, and the maker kept the original order even after switching to a drill. The spindle pulls away at the end to show the finished fine feature and the 3D milled contours around it.
What stands out to me is the cutting strategy: peck drilling with the carbide drills, no coolant, just an air blast. Sample holes were drilled successfully before the part went into the cycle, and on the deadline day the maker took a conservative approach, which seems like a sensible call under time pressure.
The open question is that drilling the actual part still snapped the bits after the samples succeeded, and the exact cause was never confirmed, though the maker thinks the breakages were most likely their own fault.