Macor
also Machinable Glass Ceramic, MGC
Macor is a machinable glass-ceramic developed by Corning, with about 55 % fluorophlogopite mica platelets dispersed in a borosilicate glass matrix; cracks deflect along the mica flakes, so it can be turned, milled, drilled and tapped with ordinary carbide tooling with no post-machining firing and no shrinkage.
Reference datasheet — Macor is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the As Fired condition
Macor tempers and conditions
Macor is supplied in one standard condition, As Fired. As Fired is the default FabDigit quotes; the values on this page are for it.
What is Macor?
Macor is a machinable glass-ceramic developed by Corning, with about 55 % fluorophlogopite mica platelets dispersed in a borosilicate glass matrix; cracks deflect along the mica flakes, so it can be turned, milled, drilled and tapped with ordinary carbide tooling with no post-machining firing and no shrinkage. It is fully non-porous, outgasses very little, insulates well and runs continuously at 800 °C with a 66.9 GPa modulus, which suits vacuum-chamber insulators, fixtures, probe holders and semiconductor and spacecraft parts. Limits are low strength and toughness (flexural strength about 94 MPa), moderate thermal shock resistance and high unit price, so it should not carry structural or impact loads; alumina is the alternative where strength outweighs machinability. Macor has a density of 2.52 g/cm³ (0.091 lb/in³), lighter than 81% of ceramic grades. Macor has a tensile strength of 34 MPa (4.93 ksi), weaker than 72% of ceramic grades. Elongation at break is 0% and the elastic modulus is 66.9 GPa (9.7 Msi).
What is Macor used for?
- Vacuum chamber feedthroughs and insulators
- Probe holders and test fixtures
- Semiconductor process fixtures
- High-voltage standoffs and spacers
- Spacecraft insulating components
- Aerospace radomes
- Welding torch nozzle insulators
Advantages
- Easy to machine — 60/100, better than 88% of ceramic grades
- Lightweight — 2.52 g/cm³ (0.091 lb/in³), better than 81% of ceramic grades
- Good corrosion resistance — 88/100, better than 77% of ceramic grades
Limitations
- Poor heat conductor — 1.5 W/m·K (0.844 BTU/hr·ft·°F), worse than 93% of ceramic grades
- Hard to polish — 55/100, worse than 85% of ceramic grades
- Low stiffness — 66.9 GPa (9.7 Msi), worse than 81% of ceramic grades
Macor properties
Typical room-temperature values for Macor-As Fired; bars are the position among ceramic grades.
Physical2
Macor has a density of 2.52 g/cm³ (0.091 lb/in³), lighter than 81% of ceramic grades.
Mechanical12
Macor has a tensile strength of 34 MPa (4.93 ksi), weaker than 72% of ceramic grades. Elongation at break is 0% and the elastic modulus is 66.9 GPa (9.7 Msi).
Thermal5
Macor is rated for continuous service to 800°C (1,472 °F). It conducts heat at 1.5 W/m·K (0.844 BTU/hr·ft·°F), worse than 93% of ceramic grades. Thermal expansion is 9.3 µm/m·K (5.17 µin/in·°F).
Electrical5
Macor is an electrical insulator with a dielectric strength of 40 kV/mm (1,016 V/mil) and a resistivity of 1×10¹⁴ Ω·m.
Chemical & Environmental2
Corrosion resistance is excellent (88/100), better than 77% of ceramic grades.
Sustainability3
Producing a kilogram of Macor takes about 70 MJ of energy and emits 5.5 kg of CO₂ — less than 71% of ceramic grades. Typical recycled content is 0%.
Manufacturability2
Macor's machinability is good (60/100, better than 88% of ceramic grades).
Common Calculations4
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the ceramic family
Yield strength against density for every ceramic grade FabDigit runs. Macor is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Macor
Is Macor easy to machine?
Machine dry with sharp carbide or diamond-coated tooling at moderate speed and light feed; holds ±0.013 mm and 0.5 µm Ra without any post-fire step — chip out at through-hole exits is the main risk.
Can Macor be welded?
Not weldable; join by metallizing and brazing, glass frit sealing, or high-temperature ceramic adhesive/mechanical clamping.
Can Macor be formed, bent or molded?
Supplied as ceramized rod/plate/block only — no plastic forming; net shape is obtained entirely by subtractive machining.
Macor chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| SiO2silica | 44 – 48 | 46 |
| MgO | 16 – 18 | 17 |
| Al2O3 | 15 – 17 | 16 |
| K2O | 9 – 11 | 10 |
| B2O3 | 6 – 8 | 7 |
| Ffluorine, forms fluorophlogopite mica crystals | 3 – 5 | 4 |
What surface finishes work on Macor?
Lap and polish with diamond or SiC media for flatness/sealing surfaces; can be metallized (Ti/Mo-Mn, sputtered Au/Cr) for electrodes and vacuum feedthroughs.
Equivalent designations
Standards and trade names that resolve to Macor in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Trade names
- Machinable Glass CeramicMGC
How much does Macor cost?
Macor is a high-cost ceramic ($$$$), pricier than about 98% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Macor — frequently asked
What is Macor used for?
Macor is typically used for vacuum chamber feedthroughs and insulators, probe holders and test fixtures, semiconductor process fixtures, high-voltage standoffs and spacers, spacecraft insulating components and aerospace radomes. In short: easily machined glass-ceramic.
What is the tensile strength of Macor?
Macor has a typical tensile strength of 34 MPa (4.93 ksi) — weaker than 72% of ceramic grades.
Is Macor easy to machine?
Reasonably — machinability is rated good (60/100, better than 88% of ceramic grades). Machine dry with sharp carbide or diamond-coated tooling at moderate speed and light feed; holds ±0.013 mm and 0.5 µm Ra without any post-fire step — chip out at through-hole exits is the main risk.
Can Macor be welded?
Not weldable; join by metallizing and brazing, glass frit sealing, or high-temperature ceramic adhesive/mechanical clamping.
What surface finishes work on Macor?
Lap and polish with diamond or SiC media for flatness/sealing surfaces; can be metallized (Ti/Mo-Mn, sputtered Au/Cr) for electrodes and vacuum feedthroughs.
Can Macor be formed, bent or molded?
Supplied as ceramized rod/plate/block only — no plastic forming; net shape is obtained entirely by subtractive machining.
What is the maximum service temperature of Macor?
Macor is rated for continuous use to about 800°C (1,472 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does Macor cost?
Macor is a high-cost ceramic ($$$$), pricier than about 98% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- MACOR Machinable Glass Ceramic — Product Information — Corning Incorporated (2012)
- Engineered Materials Handbook Vol. 4: Ceramics and Glasses — ASM International (1991)
- Glass-ceramic property data (mica glass-ceramics) — MatWeb / Ceramic supplier data sheets (2023)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.