MIL-PRF-94/3M
TABLE II Shaft length. 1/
Length of shafts from mounting surface of resistors, (nominal)
Flatted
Slotted
Symbol
Bushings N and S
Bushings N and S
Bushings L and T
(inches ±0.313)
(inches ±0.313)
(inches ±0.313)
A
0.625
0.625
B
0.500
D
0.875
0.875
0.875
L
0.375
1/ For resistors with panel seals, the mounting surface shall be considered
the metal face of the panel seal when the seal is firmly seated against
the resistor body.
3.6 Mounting and locking nuts. The mounting nut shall be 0.078 inches thick and measure 0.313 inches across
the hexagonal flats. The locking nut shall be 0.157 inches thick and shall measure 0.313 inches across the
hexagonal flats. The thread size shall be 0.25-32 NEF-2B.
3.6.1 Internal tooth lockwasher. Internal tooth lockwasher of suitable size and when mounted, shall have a
maximum thickness of 0.045 inches.
3.6.2 Retainer rings. If retainer rings are used, they shall have a maximum thickness of 0.032 inches.
3.7 Power rating. The power rating shall be 0.5 watts for taper A resistors and 0.25 watts for taper C and F.
3.8 Torque.
3.8.1 Operating torque. The torque required to effect rotation shall be 0.50 ounce-inch minimum and 6 ounce-inch
maximum.
3.8.2 Stop torque. The torque applied to the operating shaft to the stops shall be 3 pound-inch.
3.8.3 Locking torque (as applicable). For the locking bushing type resistors, the locking nut shall be tightened with
a torque of 8 pound-inches. After the locking nut is tightened, the contact arm shall not move when a torque of 20
ounce-inches is applied to the shaft.
3.9 Total mechanical rotation. The total mechanical rotation without a switch shall be within the limits of 292
degrees and 298 degrees.
3.10 Thermal cycling. The resistance shall not change in excess of 4 percent.
3.11 Pure tin. The use of pure tin, as an underplate or final finish, is prohibited both internally and externally. Tin
content of resistor components and solder shall not exceed 97 percent, by mass. Tin shall be alloyed with a
minimum of 3 percent lead, by mass (see 6.3).
4. VERIFICATION
4.1 Sampling and inspection. Sampling and inspection shall be in accordance with MIL-PRF-94.
4.2 Dielectric withstanding voltage. In the dielectric withstanding voltage test, the applied potential shall be 750
volts rms at a atmospheric pressure, and 350 volts rms at reduced barometric pressure.
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