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| MIL-C-18087A(SH)
(b) Compressive stress of load-baring surfaces including washers at
the upper limit of installation torque shall not exceed 100
percent of ultimate compressive strength of the material.
3.4.6.7 Fastener deterioration. In order to prevent deterioration due to
corrosion, bolts, nuts, studs, pins, springs, screws, cap screws. and other
fastenings or fittings shall be of corrosion resisting material, or of a material
treated in a manner to render it resistant to corrosion. Where threaded surfaces
or close fitting surfaces may require disassembly in service, an antiseize com-
pound in accordance with MIL-A-907 shall be used. Cadmium and zinc plating are
prohibited. Substitute with QQ-S-365, MIL-C-26074, or MIL-C-83488.
3.4.7 Flanges, hubs and sleeves.
3.4.7.1 Centering. Flange connections shall be provided with a rabbet or
fitted bolts or dowels for centering. Rabbets shall be machined to achieve a
loose diametral fit not greater than 0.001 inch total or 0.001 inch per foot of
diameter, whichever is larger. Fitted bolts or dowels used in place of the rabbet
fit shall maintain equal or better concentricity at the locating diameter. Dowels
shall be positively secured and not rely on friction alone to prevent them from
coming out.
3.4.7.2 Counterboring. Flanges for main gear clutches and clutches
operating above 2200 r/rein shall be counterbored to shroud bolt head and nuts.
3.4.7.3 Hub and sleeve interface. For positive drive clutches (types V and
VI), a hub and sleeve interface shall be utilized that results in a gear-type
coupling constructed to transmit 120 percent full power torque (see 3 3.1).
Unless otherwise specified (see 6.2), hub and sleeve material shall be in accord-
ance with table I (see 3.2).
Teeth used shall be of the involute or
3.4.7.4 Hub and sleeve tooth form
modified involute form. The teeth shall accommodate the misalignment requirements
(see 6 2). When crowned teeth are required, tooth crown radius shall be
determined.
3.4.7.5 Wear margin. Hubs and sleeves for positive drive clutches (types V
and VI) shall be designed so that replacement due to wear is not required until
backlash is at least equal to design backlash plus 50 percent of case thickness
for surface-hardened teeth.
3.4.7.6 Sleeve pitch diameter concentricity. For positive drive clutches
(types V and VI) hubs used with main reduction gear assemblies, and for operating
speeds above 2200 r/rein, the pitch diameter of sleeve teeth shall be concentric
with the locating diameter within O 001 inch per foot of diameter.
3.4.7.7 Hub tooth concentricity. For positive drive clutches (types V and
VI) with toothed hubs used with main reduction gear assemblies, and for all
clutches operating above 2200 r/min, the pitch diameter of the hub teeth shall be
concentric with the bore diameter within 0.001 inch for diameters up to 12
inches, and 0.001 inch per foot for diameters over 12 inches.
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