Glass, hard ceramic, porcelain, and stone are exactly the materials that destroy ordinary bits — an HSS or carbide tip skates, chips the surface, or cracks the piece before it ever bites. For fine, delicate work on those materials, you need diamond. The Proxxon No. 28230 is a micro-fine, diamond-coated bit built for precisely that: drilling, grinding, shaping, and engraving the hardest, most brittle surfaces, cleanly.
Its spherical diamond-coated tip abrades rather than punches, so it works into glass, ceramic, porcelain, and stone up to granite hardness without the chipping and cracking that ruin detail pieces. At just 1.2mm it's made for precision — tile and glass repair, mosaic, jewelry, lapidary, and any job that calls for a tiny, controlled cut in hard material. The 2.35mm (3/32") shank is the standard size for rotary and micro tools, so it drops straight into Proxxon MICROMOT collets and other rotary tools.
Like any diamond bit on brittle material, it rewards patience: run it around 2,000 RPM with water or coolant on a drill press, and it cuts clean and lasts. It comes as a 2-pack so you have a spare for the next job. This bit is also one of the diamond consumables in the Proxxon-DiStar Cut & Polish Essentials Kit.
Pro tip: Let the diamond do the work — light pressure, ~2,000 RPM, and a steady drip of water. Forcing a brittle material is how you crack it; ease the tip in, keep it cool, and back off at breakthrough. A drill press gives you the control a fine bit like this needs.
