MIL-DTL-13931J
18264. If the tests indicate the material to be satisfactory for use, it shall be consumed within six months
from date of completion of tests; otherwise the unused material shall be re-tested similarly.
3.4.6
Assembly.
3.4.6.1 Preparation for assembly. All parts shall be free of metal chips, dirt and other foreign material,
and shall be properly lubricated at the time of assembly.
3.4.6.2 Fitting. All parts shall assemble readily; however, some force may be necessary due to "FREE
STATE VARIATION" permitted on drawings. Parts to be fastened together by rivets, bolts, welding or
similar means, shall fit each other properly before assembly and shall not be drawn or drifted to a fit by
bolts, rivets or other means of strain. With the exception of surfaces where uniform contact or bearing is
specified, parts shall not be filed, scraped or otherwise altered to obtain proper fitting. If metal removing
operations are required during assembly, all parts contaminated with metal chips or foreign matter shall
be cleaned, refinished (if necessary), re-lubricated and reassembled.
3.4.6.3 Reduction of chamber and tube diameters. When hoops are specified for cannon tube assembly,
reduction of the chamber and bore across diameters due to heat shrinkage of the hoop shall be limited to
.002 inch. This reduction shall apply for the length of each hoop plus any transition zones.
3.4.6.4 Functioning. Assembled items shall function smoothly without interference. Any defects in
operation due to defective parts or incorrect assembly shall be corrected by the supplier.
3.4.6.4.1 Obturator surfaces. The surfaces of obturator pads and the metal surfaces against which the
pad seats shall be free from oil and grease. When metallic-ring breech seals are prescribed, the sealing
surfaces and mating seats shall be free from any foreign matter.
3.4.6.4.2 Bearing of obturator parts. When the breech is closed each outer split ring shall have 360
degrees of contact with the seating surface in the tube, with not less than 80 percent of the seating area of
each ring in contact with the tube. Metallic-ring breech seals shall have 360 degrees of contact with the
mating seating surfaces.
3.4.6.5
Lubrication.
3.4.6.5.1 Mating surfaces. All contact surfaces of metal parts, except surfaces on which freedom from
lubricant is specified and bearing surfaces for hot rivets or fused joints, shall be coated immediately
before assembly with a film of preservative lubricating oil conforming to MIL-PRF-3150.
3.4.6.5.2 Threaded joints. Threaded joints larger than one inch diameter shall be coated to fill the thread
clearance with grease conforming to MIL-PRF-81322. This requirement shall apply to the mating
threads of the following:
a.
Breech ring and breech bushing.
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