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Macor® MGC
(Machinable Glass Ceramic) Specifications

904 West 6th Street, Shiner, Texas 77984 USA
Phone: 1-361-594-2941     Fax: 1-361-594-2349     E-Mail:


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Macor Material (c) Boedeker Plastics 2001 Macor® is a white, odorless, porcelain-like (in appearance) material composed of approximately 55% fluorophlogopite mica and 45% borosilicate glass. It contains the following compounds (in weight percent):
• Silicon ( Si O2 ) 46%   • Magnesium ( Mg O ) 17%   • Aluminum ( Al2O3 ) 16%   • Potassium ( K2O ) 10%   • Boron ( B2O3 ) 7%   • Fluorine ( F ) 4%  

Macor® Machinable Glass Ceramic is has a continuous use temperature of 800°C. Its coefficient of thermal expansion readily matches most metals and sealing glasses. It is nonwetting, exhibits zero porosity, and unlike ductile materials, won't deform. It is an excellent insulator at high voltages, various frequencies and high temperatures. And when properly baked out, it won't outgas in vacuum environments. Macor® is WHITE in color.

Macor® may be machined using standard metal working tools and operations, including lathes, drills, mills, and machining centers. Macor® machining tolerances are surprisingly tight, up to .0005". It can be machined to a surface finish of less than 20 µin. and polished to a smoothness of 0.5 µin.-AA finish.

High speed steel tools may be used, but carbide tools are recommended for longer wear. Water-soluble coolants which are recommended for glass or ceramics should be used, such as Cimstar-40 Pink. No post firing is required after machining. Recommended equipment, feeds and speeds include:
    • Grinding --- diamond, silicon-carbide or aluminum-oxide grinding wheel
    • Sawing --- 100 fpm band speed carbide grit, silicon-carbide or diamond wheel
    • Turning --- 30-50 sfm, .002-.005 ipr, .150” cut depth
    • Milling --- 20-35 sfm, .002 ipt, .150”-.200” cut depth
    • Drilling --- ¼” dia - 300 rpm, .005 ipr   /   ½” dia - 250 rpm, .007 ipr   /   1” dia - 100 rpm, .010 ipr

Macor® MGC can also be joined or sealed - both to itself and to other materials - in a number of ways: metalized parts can be soldered together and brazing has proven an effective method of joining the material to various metals; epoxy produces a strong joint, and sealing glass creates a vacuum tight seal. Even a straightforward mechanical joint is possible. It can be thick film metalized using metal inks, or thin film metalized by sputtering.

• Ultra High Vacuum Environments • Constant Vacuum Applications - microwave spacers, headers, windows • Aerospace Industry - retaining rings, radiation detectors • Nuclear-Related Experiments - reference cubes • Welding Nozzles • Fixtures, Electrodes, Burner Blocks • Medical Equipment

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ASTM or UL test Property Macor® MGC
D792 Density (lb/in³)
D570 Water Absorption, 24 hrs (%) 0.01
D695 Compressive Strength (psi) 50,000
D790 Flexural Strength (psi) 13,600
- Modulus of Elasticity (psi) 9,700,000
- Shear Modulus (psi) 3,700,000
- Poisson's Ratio 0.29
D785 Hardness, Rockwell A48
D696 Coefficient of Linear Thermal Expansion
(x 10-6 in./in./°F)
D648 Heat Deflection Temp (°F / °C)
at 264 psi

240 / 116
D3418 Melting Temperature (°F / °C) none
- Max Operating Temp (°F / °C) 1832 / 1000
C177 Thermal Conductivity
(x 10-4 cal/cm-sec-°C)

UL94 Flammability Rating none
D149 Dielectric Strength (V/mil) short time, 1/8" thick 1000
D150 Dielectric Constant at 1 KHz 6.03
D150 Dissipation Factor at 60 Hz -
D257 Volume Resistivity (ohm-cm)at 50% RH > 1016

NOTE: The information contained herein are typical values intended for reference and comparison purposes only. They should NOT be used as a basis for design specifications or quality control. Contact us for manufacturers' complete material property datasheets.
All values at 73°F (23°C) unless otherwise noted.
MACOR is a registered trademark of Corning Incorporated
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Boedeker Plastics, Inc.
904 West 6th Street, Shiner, Texas 77984 USA
USA TOLLFREE : 1-800-444-3485
Phone: 1-361-594-2941     Fax: 1-361-594-2349     E-Mail:

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