Macor® is a machinable glass ceramic known for its ability to withstand high temperatures while maintaining tight tolerances. Developed by Corning Glass Company, Macor® offers a balance between the properties of true ceramics and the ease of machining. This solid white mica glass ceramic is composed of approximately 46% silica, 17% MgO, 16% Al2O3, 10% K2O, 7% B2O3, and 4% F.

Much like fused quartz, Macor® remains stable at temperatures up to nearly 1000°C, exhibiting very low thermal expansion and minimal thermal or electrical conductivity, outperforming most high-performance plastics. It is non-porous, has good technical strength, and does not outgas at high temperatures. Its standout feature is its machinability using conventional HSS single point cutting tools, though carbide tools are recommended for longer tool life.

Machining Macor® generates hard drilling chips and grinding swarf, which can cause abrasion to machine ways over time. High volumes of coolant are recommended during machining. The ability to machine this “ceramic” material with conventional tools allows engineers to quickly fabricate development prototypes in-house.

For some applications, Macor® may be sufficient for final production. However, for higher hardness at elevated temperatures, materials like Aluminum Oxide, Silicon Carbide, or Zirconia are preferable. Corning produces Macor® in sizes up to 12 inches in maximum dimension. Stocking distributors offer standard raw material sizes in plates, bars, and rods within this limitation.

Macor® is valuable for cutting-edge applications in aerospace, semiconductor, medical, and laboratory fields. Its stability is ideal for fixtures, and its non-gassing property makes it suitable for ultra-high vacuum environments.