Alumina ceramic is hard, brittle and electrically insulating, which is exactly why it is specified — and exactly why it cannot be machined like a metal. It is ground, not cut.
Alumina (aluminium oxide, Al2O3) is a technical ceramic with very high hardness, excellent wear resistance, high temperature capability and strong dielectric properties. Common grades run from 95% to 99.9% alumina content: 95-97% for general industrial parts, 99% and above for high-purity semiconductor, insulation and high-wear applications, where higher content improves dielectric strength, wear resistance and thermal behaviour. Because it has almost no plastic deformation, the material does not yield at the cutting edge — it fractures, which is what makes edge quality and fixturing the deciding factors.
Only diamond tooling removes alumina effectively. Cutting depths are small, feeds are controlled, and the process is closer to precision grinding than to milling.
Point loads and vibration cause chipping. Fixturing distributes force, and features are approached so edges are supported rather than broken out.
Alumina conducts heat poorly, so a sudden temperature change can crack a part that survived machining. Cooling is moderate and controlled, not aggressive.
Sharp internal corners concentrate stress. Small chamfers and radii are machined deliberately to protect the part in service.
Semiconductor process and plasma components, vacuum feedthroughs and insulators, electrical insulation and wear parts, medical and analytical equipment, aerospace components.