SUPER FINE
V-1
NMC
Clear
Microwave windows, large transmitter capacitors, special high quality optics, air regulating diaphragms, Geiger-Muller counter windows, metalized resistance cards, bolometers.
INDICATOR OF COMPARATIVE VALUE 100
V-2
NMS
Clear& Slightly Stained
INDICATOR OF COMPARATIVE VALUE 65
CAPACITOR QUALITY
V-3
NMF
FAIR STAINED
Capacitors for radio transmitters and general electronic purposes. Mica has low power loss and high “Q” values.
INDICATOR OF COMPARATIVE VALUE 45
V-4
NMG
GOOD STAINED
Capacitors for radio receivers. “Q” is slightly lower. Excellent for all average applications in radio and electronic work.
INDICATOR OF COMPARATIVE VALUE 32
RADIO TUBE QUALITY
V-5
NMSA
STAINED A
High quality radio tube spacers, lowest quality for used for small capacitors
INDICATOR OF COMPARATIVE VALUE 14
V-6
NMSB
STAINED B
INDICATOR OF COMPARATIVE VALUE 12
CLEAR ELECTRIC
V-7
NMH
Heavy Stained
Thermostat insulators, lower quality tube spacers, fuse windows, neon electrodes, heating elements. Highest quality for needed for low voltage applications.
INDICATOR OF COMPARATIVE VALUE 10
SPOTTED ELECTRIC
V-8
NMDB
Black Dotted
Appliances, 110/220-volt insulation, transformer layer insulation.
INDICATOR OF COMPARATIVE VALUE 5
V-9
NMBS
Black Spotted
Dots and Spots are non-conductive; however, mica has a small amount of surface leakage.
INDICATOR OF COMPARATIVE VALUE 4
STAINED ELECTRIC
V-10
NMBS
Black Stained
Motors, appliances and resistors, Stains are conductive at high voltage and more surface leakage.
INDICATOR OF COMPARATIVE VALUE 3
ASTM and Federal Specifications may be used at any time as we are able to furnish certificate of compliance on any products fabricated. Following are some of the applicable specifications.
ASTM-D-351 – Visual Quality Mica
ASTM-D-748 – Mica for Fixed Capacitors
HH-I-536 – Visual Quality Mica
HH-I- 538 – Electrical Pasted Mica
Properties of Mica (MUSCOVITE, Compiled by the U.S. Bureau of Mines)
Mechanical
Density:
Gr./Cu. Cm ............................................................................................ 2.6-3.2
Lb./Cu. Ft. ............................................................................................. 160-200
Hardness, Mohs .................................................................................... 2.0-3.2
Cleavage ................................................................................................ Basal, Eminent
Crystal Structure .................................................................................. Monoclinic
Max Temperature with no decomposition .......................................... 400-500⁰C
Specific Heat(25⁰C) ............................................................................... .206-.209
Thermal conductivity perpendicular to cleavage:
Cal./Sq. Cm./Sec./Cm./⁰C ...................................................................... 16x10-⁴
B.T.U./ Sq. Ft./Hr./In. ⁰F ........................................................................... 4.6
Coefficient of expansion per ⁰C perpendicular to cleavage:
20⁰-100⁰C ................................................................................................ 15x10-⁶-- 25x10-⁶
100⁰-300⁰C .............................................................................................. 15x10-⁶ -- 25x10-⁶
300⁰-600⁰C ............................................................................................... 16x10-⁶ -- 36x10-⁶
Coefficient of expansion per ⁰C parallel to cleavage:
0⁰-200⁰C .................................................................................................... 8x10-⁶ -- 9x10-⁶
200⁰-500⁰C ................................................................................................ 10x10-⁶--12x10-⁶
Tensile Strength, P.S.I. ............................................................................... 37,000-43,000
Modulus of elasticity ................................................................................. 25x10⁶
Electrical
Dielectric Constant ................................................................................... 6.5-9
Dielectric Strength (highest Qualities 1-3 mils thick), Volts/Mil. ............. 6,000-3,000
Power Factor at 25⁰C (77⁰F) (highest qualities), percent:
60 cycles .................................................................................................... 0.08-0.09
1 megacycle ................................................................................................ 0.01-0.02
Resistivity, Ohm-Cm..................................................................................... 10¹²-10¹⁵
OPTICAL
Optic axial angle (2V) degrees.................................................................... 38-47
Orientation of optic plane to plane of symmetry .................................... Perpendicular
Indexes of refraction:
∂.................................................................................................................. 1.552-1.570
β.................................................................................................................. 1.582-1.607
ɤ.................................................................................................................. 1.588-1.611
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