MIL-DTL-17060G(SH)
3.5.2.5.7 Frames and end shields. The diameter bolt circle for the clearance holes of the end bracket shall have
a tolerance not greater than 25 percent of the tolerance of the clearance holes. The angular position of these
clearance holes shall have the same tolerance as the tapped holes in the frame.
3.5.2.5.8 Covers, plates, and hoods. The use of flat covers, plates, and hoods should be avoided. Enclosures
shall be stiffened by the use of ribs, formed shaping, and similar measures. Natural frequencies of all major parts
shall be greater than 1.4 times the maximum frequency of exciting forces most likely to force them into vibration,
such as mechanical unbalance, magnetic effects, and fan blade effects.
3.5.2.5.9 Caution plate. A plate bearing the caution "LOW NOISE MOTOR - HANDLE WITH CARE" shall
3.5.2.5.10 Dynamic balance. Unless otherwise specified (see 6.2), the degree of balance shall be super-
precision as specified in table V.
3.5.2.5.11 Lubrication provisions. Except for motors with Type 111, Class 8 or Type 120 bearings, motors
shall be relubricable and shall not require disassembly for relubrication. Grease cups, pipes, and drains shall be used
when grease is a means of lubrication and relubrication of bearings is required. The grease cup shall not be mounted
on the motor and the threaded hole used to attach the grease cup shall be provided with a pipe plug or cap. Grease
inlet and drain passages shall be of minimum length and shall be cleanable without motor disassembly other than
removal of any grease pipes. Grease pipes shall be removable without motor disassembly. Grease pipes, where
used, shall be left on the motor; the end outermost from the motor shall be fitted with a pipe plug or cap. Pipe plugs
or caps shall be accessible without motor disassembly. The grease inlet shall be located on or above the horizontal
centerline of the bearing housing for horizontal motors and at any location convenient to the grease chambers above
the bearing for vertical motors. Grease outlets shall be located to afford maximum purging of grease during
regreasing operation.
3.5.2.5.12 Interchangeability. Bearing caps, bearing cap fasteners, end bells, end bell fasteners, air baffles,
removable fans and parts that affect lubrication that are physically interchangeable shall be functionally
interchangeable. The above parts that are physically reversible shall be functionally reversible.
3.5.2.5.13 Special bearings preload. When special preload requirements are specified (see 6.2 and B.2 of
Appendix B), the following shall be applicable:
a. Selective fitting of bearing preload washers and springs shall be prohibited. Preload washers and springs
shall meet the following (see 4.6.21):
(1) The preload washer or spring, after being fully compressed, shall be self-restoring to its original free
height.
(2) The preload washer or spring, when compressed to the nominal design compression, shall produce a
force within the range determined to be acceptable for the application.
b. Parts not normally replaced that affect the dimensional allowance in the bearing housing for the preload
washer or spring may be machined after initial assembly to achieve the appropriate allowance. It is acceptable for
additional material to be designed into a part to provide an allowance for the above machining. After machining, the
part shall be in accordance with the requirements of the affected part drawing.
3.5.2.6 Motors for low noise applications (surface ships only). Unless otherwise specified (see 6.2), motors for
low noise applications (see 6.6.14) on surface ships shall meet Service A requirements (see 3.5.2.1) and shall be as
3.5.2.6.1 Ball bearings. The requirements of 3.5.2.1.5 are applicable with the exception that ball bearings shall
be in accordance with MIL-B-17931.
3.5.2.6.2 Shafts. Keyways which extend up to the bearing seat shall be end milled. Keyways shall not extend
under the bearing more than absolutely necessary and under no circumstances under the ball track.
3.5.2.6.3 Dynamic balance. Unless otherwise specified (see 6.2), the degree of balance shall be super-precision
in accordance with table V.
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