immediately after they have been cleaned and washed. If they are to be stored before remounting, coat them with clean high grade oil or petroleum and wrap in clean, oil-proof paper. Petroleum solvents are inflammable and must be used with caution because of the fire hazard involved. Carbon tetrachloride or similar solvents are sometimes used because they are non-inflammable, but their use is discouraged in cleaning bearings because they leave the bearing surfaces bone dry and subject to rust. Compressed air is sometimes used to blow out bearings, but it is not recommended unless the air is free from dirt and moisture. If used, the bearings must be held so as to prevent spinning which may cause scoring of the bearing surfaces by dirt. The ball bearings of horizontal machines only may, if desired, be cleaned without disassembling the motor, by the following method: Remove the filler and drain plugs and free the holes of any hardened grease. Flush a light oil heated to about 190°F through the housing while slowly rotating the shaft. Repeat until the oil comes out clean indicating that most of the old grease has been removed. In cases where the grease has become body oxidized, a preliminary flushing with a hot aqueous emulsion may be required, followed, if necessary, by flushing with a mixture of alcohol and light mineral solvent. should always be with hot light oil. The final flushing Relubricate in accordance with the recommendation given in the instructions for lubrication of ball bearings. BEARING WEAR A ball bearing is subject to negligible friction wear unless the lubricant becomes contaminated with abrasive material. Thus, if properly lubricated, a ball bearing will not wear gradually, and air-gap measurements are unnecessary. If ball bearings fail, they will do so ina 3-50