MIL-DTL-25867D
3.3.2 Adjustment mechanism. If the gage is provided with a means for adjusting or
correcting the indications, it shall be simple to manipulate and designed so that adjustments can
be made without the use of special tools. The means of adjustment need not be outside the case.
3.3.3 Gage mechanism. The gage mechanism shall be comprised of units distinct from
the case. The gage shall be sufficiently rugged so that small distortions of the case will not
affect accuracy of the indication.
3.3.4 Case. The case dimensions shall be in accordance with MS24478. The case body
shall be made of nonferrous low-density metal, shall be uniform in texture, shall have a smooth
surface, and shall be manufactured to be rain tight.
3.3.4.1 Vent. The case shall be vented with a hole having a diameter of at least
0.0675 inch. If the hole is plugged, it shall be filled or closed with a permanent porous plug or
sealing device that will release or blow out if the pressure sensing element in the gage should
fail. There shall be no failure of the cover glass or any portion of the gage casing due to failure
of the internal sensing element.
3.3.5 Mounting nuts. When attached insert nuts are used, each mounting lug shall be fitted
with 0.138-32 UNC-2B self-locking insert nuts that shall be attached to prevent loosening under an
axial load of 25 pounds and to prevent turning under a torque of 10 inch-pounds.
3.3.6 Boss. The boss on the gage shall conform to AND10050. Flats shall be provided
on the side of the boss for a minimum distance of 3/8 inch to permit use of a wrench to tighten
the mating fittings.
3.3.7 Restrictor. The gage shall be provided with a restrictor orifice having an internal
diameter of 0.008 ± 0.0015 inch, a maximum length of 0.156 inch, and a minimum length of
0.0625 inch.
3.3.8 Overpressure stop. The gage shall be provided with an overpressure stop designed
to restrain the prime mover thereby limiting the pointer travel to a minimum of 0.062 inch
beyond the full scale graduation.
3.3.9 Pointer. A pointer shall be provided and shall have a width at the tip end of
0.017 inch ± 0.003 inch and an increasing taper of approximately 0.031 inch per inch or a width
of 0.031 inch ± 0.008 inch along its entire length. The length of the pointer shall be such that
the tip will extend into the scale a distance of one-third to two-thirds the length of the shortest
graduation.
3.3.9.1 Pointer finish. The visible portion of the pointer shall be finished with lusterless
white, color number 37875 of FED-STD-595.
3.3.10 Dial. The dial shall be constructed of metal and the dial configuration shall
conform to figure 1. The calibration arc for each type specified herein shall be a minimum of
55 degrees on a 0.75 inch radius with the pivot point located on the vertical center line,
0.406 inch below the horizontal centerline.
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