Tips for Using a Pearl Drilling Machine on Glass

Hi everyone,
I’m starting to drill small, clean holes in glass pieces (similar to what you’d do for beads/pendants), and I’ve been experimenting with a pearl drilling machine (the small vertical drill press style used in jewelry work). Here are a few practical notes that helped me get better results—hope this is useful, and I’d love your feedback too.

What seems to matter most
Diamond drill bits: Regular twist bits chip the glass easily. Small diamond core bits or diamond-coated bits work much better.
Water cooling: A constant drip or shallow water bath keeps the bit cool and reduces cracking.
Low speed + light pressure: Let the diamond do the cutting. Pushing hard increases heat and causes chips.
Start with a guide: A small template, tape, or a drilling guide helps prevent the bit from “skating” on the glass surface.
Support the back side: Placing the glass on a flat support (rubber pad/wood) reduces breakout when the bit exits.
My current workflow
I mark the hole, apply tape, start at a slight angle to “seat” the bit, then level out and drill slowly with water running. When I’m close to breaking through, I reduce pressure even more to avoid chipping on the back.

Do you prefer drilling halfway from each side to minimize breakout, or is one-pass drilling fine if the setup is stable? Also, any recommendations for reliable diamond bit brands for tiny holes (like 1–2 mm)?

Thanks in advance!
 
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