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Frequently Asked Questions
How is machinable glass ceramic machined?
With conventional carbide tooling on standard lathes and mills - turning, drilling, tapping and milling all work without diamond tooling or specialist equipment. Parts are cut to final dimensions and used straight away, because there is no firing step afterwards and therefore no shrinkage allowance to calculate.
Why can it be machined when other ceramics cannot?
Its structure contains interlocked mica platelets dispersed through a glass matrix. As the tool passes, micro-cracks form and are immediately deflected and arrested at the platelet boundaries rather than running through the part. Material is removed as fine local fracture at the cutting edge instead of the workpiece splitting.
What temperature can it withstand?
Around 800 degrees Celsius continuously, with a higher short-term peak, which places it below alumina and the non-oxide ceramics but far above any polymer. It has low thermal conductivity, so it also serves as a thermal insulator and heat break as well as a structural part.
Is it suitable for vacuum applications?
Vacuum work is one of its principal uses. The material is non-porous and does not outgas, so it will not contaminate a chamber or prevent a system reaching pressure, and it can be machined into the complex feedthroughs, fixtures and insulating supports that vacuum equipment needs in small quantities.
What are its mechanical limitations?
It is substantially weaker and softer than alumina, zirconia, silicon carbide or silicon nitride, and it is not a wear-resistant material. It should not be specified for abrasive service, high mechanical load or impact. Its value is fabrication convenience combined with electrical and thermal performance, not strength.
Can it be metallised or joined?
It can be bonded with adhesives and epoxies, and joined to metals with careful attention to differential thermal expansion. It does not accept the standard metallising and brazing routes developed for alumina, so where a hermetic ceramic-to-metal seal is needed alumina remains the usual material.
When should I choose it over alumina?
When the part is a one-off, a prototype, or a complex shape in small numbers, and the duty is electrical insulation or thermal isolation rather than wear. The saving is in fabrication - no diamond grinding, no tooling lead time. For production quantities of a wear or high-temperature part, alumina is both cheaper and better.