MIL-DTL-197L
TABLE I. Methods of unit preservation by size or type.
Open/closed bearings 1
Size or type
MIL-DTL-197 method
41B
Up to and including 1.1811 inches
or 30 millimeters (mm) (metric) outside diameter (OD) 2
44B
46B
52B
55B
20B
Over 1.1811 inches or 30 mm (metric)
but not exceeding 16 inches OD 2 3
40B
41B 4
Greater than 16 inches OD or 406 mm (metric)
49B
or greater than 10 pounds (lbs.)
32B
Plain bearings, self-aligning bearings, rod end bearings,
33B
sleeve bearings, and airframe bearings
Optional methods (see 3.3.1)
45B
54B
1
Cleaning and drying shall apply only to open, non-lubricated bearings.
2
Method 40B is required for bearings to MIL-B-17931.
3
Method 20B may be used for bearings with OD over 4.86 inches or over 123 mm.
4
No weight limit when used with supporting container (MIL-DTL-117, type I, heavy duty).
3.3.2 General preservation process. Unless otherwise specified (see 6.2), all bearings
shall be subject to a general preservation procedure. The details of that procedure are
determined by bearing type, closure, and contract or purchase order requirements. The general
procedure consists of the following steps: demagnetization, cleaning, drying, preservation,
lubrication, intimate bagging or wrapping, and unit packaging. These steps are not listed in
sequence and additional steps may be required.
3.3.3 Demagnetization, cleaning and drying. Prior to cleaning, the magnetization of
instrument precision ball bearings shall not exceed a pole strength of two gauss and the
magnetization of all other bearings shall not exceed a pole strength of five gauss. Bearings in
excess of the applicable value shall be demagnetized and retested. Bearings shall be cleaned and
dried according to type and closure and contract or purchase order requirements. Pre-lubricated
bearings shall not be subjected to the cleaning process. Processed bearings shall be free of any
chemical or particulate residue that will have detrimental effect on the life of the bearing.
3.3.4 Lubricants and preservative compounds. Lubrication of bearings and actual
lubricants used shall conform to government prime contract item description requirements. Any
resultant flow-down of item description requirements to a packaging facility shall include the
same item description information (see 3.1.4.1). When lubrication is not applicable, then a
contact preservative compound shall be applied in accordance with contract or purchase order
requirements. When the bearing item description does not specify a contact preservative
compound, then the preservative material shall be as specified in table II. Self-lubricating
bearings, as described within this document, shall not have lubricants or preservative compounds
applied.
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