MACOR® Machinable Glass Ceramic Sheet

MACOR® consists of interlocking plate-like mica crystals in a glassy matrix. These crystals stop microscopic fractures at the tool tip from spreading through the material, allowing it to be machined in a controlled way. During machining, the tool pulverises the surface into a fine powder of crystals and glass — and because the crystals are so small, the machined surface finish is good. Its characteristics differ from metals and plastics, so it is worth spending a little time on simple trial cuts (drilling, turning, milling) to learn how the material behaves before machining a finished component.

Tungsten carbide tools are highly recommended. High speed steel tools can be used, but ceramic-tipped tools are not advised. Watch for the warning signs of a dull tool: if the tool squeaks, if the MACOR® surface turns greyish through tool wear, or if too much force is needed, stop and sharpen the tool. As a general rule, machine at lower speeds, keep the workpiece cool, and take smaller depths of cut until you are confident with the material — it is usually the required surface finish that controls machining speed.

No. Unlike conventional ceramics, MACOR® requires no post-machining firing, sintering, or heat treatment of any kind. Once machining is complete, the component simply needs to be cleaned and it is ready for use. This is what allows precision ceramic parts to be produced entirely in a standard machine shop, without ceramic-specific processing equipment or the dimensional uncertainty that firing introduces.

Yes. Although MACOR® is a high-temperature material, the best machining results come from keeping both the material and the tool cool. Water-soluble cutting fluids improve the cutting action, trap and wash away machining debris, and protect your machine tools. If the fluid is recirculated, use a settling tank — the powder generated during machining is somewhat abrasive, so cleanliness and machine maintenance deserve extra attention.

Use a carbide grit blade at a band speed of around 30 m/min, or a diamond or silicon carbide cut-off wheel. Keep the cut cool with water-soluble coolant and support the sheet evenly to avoid shock loading — MACOR® is a brittle material, so physical shock should always be avoided.

With carbide-tipped tools, suggested turning speeds are around 600 rpm for 5–10 mm diameter work, reducing to around 400 rpm at 25 mm diameter. Feed rates of 20–30 mm/min work well, with a depth of cut of 2–4 mm for roughing and under 1 mm for finishing. Side and back rake angles and end and side relief angles should be around 5°, with a side cutting edge angle of 15°–45° and a nose radius larger than 0.8 mm. Thread cutting is also possible at low spindle speeds, with a typical cutting depth of 0.025–0.040 mm per pass.

Typical head speeds are 1,000–1,500 rpm with a chip load of 0.05 mm per tooth, and depths of cut as for turning (2–4 mm roughing, under 1 mm finishing). Use climb milling — it prevents material being pulled off the edge of the workpiece, which is the most common cause of edge chipping when milling MACOR®.

For holes up to about 5 mm diameter, a spindle speed of 1,000–1,500 rpm and a feed rate of 20–30 mm/min is effective. Relieve the drill flutes constantly — especially on small-diameter holes — and check drill sharpness every 25–50 holes. Use a slow feed at the start and finish of each hole, and to prevent breakout when drilling through-thickness, either use a backing plate or chamfer the hole entrance and exit before drilling through. MACOR® can also be ultrasonically drilled where very fine or unconventional hole geometries are required.

Yes. Make the clearance hole one size larger than recommended for metal (typically 0.1–0.2 mm larger) and chamfer both ends of the hole to prevent chipping. A 4-flute tap is preferable to a 2-flute tap. Run the tap slowly and in the same direction throughout — turning the tap back and forth can cause chipping — and flush with water or coolant to remove dust. Where threads will see repeated assembly, wire thread inserts can be used with MACOR®.

Diamond grinding wheels give the best results, although silicon carbide and alumina wheels can also be used — always with water cooling. For polishing, start with a 400 grit silicon carbide before moving to alumina or cerium oxide powders for the final finish. A polished MACOR® surface also improves arc resistance in high-voltage insulation applications.

MACOR® is not resilient, so when machining small or delicate pieces make sure the clamping load is uniformly distributed — use soft jaws where possible. Avoid physical shock at every stage: in workholding, in tool engagement, and in handling between operations. Gentle, even support and controlled cutting forces are the foundation of successful MACOR® machining.

MACOR® has a continuous use temperature of 800 °C and a maximum no-load (peak) temperature of 1,000 °C. Unlike high-temperature plastics, it will not creep or deform under sustained thermal load, maintaining its structural integrity, dimensional stability, and electrical insulation performance throughout — making it reliable in furnaces, high-temperature processing equipment, and thermal break applications.

Yes. MACOR® has zero porosity and does not outgas, making it fully compatible with high-vacuum and ultra-high-vacuum environments. It can be hermetically sealed, joined, and metallised, which supports its use in vacuum feedthroughs, coil supports, and sealed assemblies. Its coefficient of thermal expansion is readily matched to most metals and sealing glasses, reducing thermally induced stress at joints and interfaces.

Choose MACOR® when in-house machinability, electrical insulation, and vacuum compatibility are the priorities. If you need significantly higher thermal conductivity in a machinable ceramic, Shapal® Hi-M Soft or BNP-2 aluminium nitride are the natural alternatives. If you need greater hardness, wear resistance, or higher temperature capability — and can accept conventional ceramic processing rather than in-house machining — alumina (Al₂O₃) is the obvious choice. We stock all of these and can advise on the best fit for your application.

MACOR® sheet is available in thicknesses from 0.5 mm to 35 mm and widths and lengths from 25 mm to 150 mm, with no minimum order quantity. If you'd rather receive a finished component than machine the sheet yourself, our in-house machining service can cut, mill, drill, tap, and grind MACOR® to your drawing — including micromachined features. Larger blanks, slabs, rods, and bars, as well as fully custom configurations, are available — please contact us.