wipe clean those portions of the housing around the filler and drain plugs. Remove the drain plug and free the drain hole of any hardened grease which may have accumulated, With the machine running, add new grease through the filler hole until it starts to come out of the drain. Before replacing the drain plug, let the machine run for ten to twenty minutes to expel any excess grease. The filler and drain plugs should be thoroughly cleaned before they are replaced. CLEANING BALL BEARINGS At such times as the machine is disassembled for general overhauling, the housing may be cleaned of old oil or grease by washing with carbon tetrachloride. Open-type bearings may be cleaned by placing them in wire basket suspended in a container of clean, cold petroleum solvent or kerosene and permitting them to soak for several hours. In stubborn cases, agitation in a hot oil bath may prove more expedient. Use a light transformer, spindle, automotive flushing, or motor oil not heavier than SAE-10 heated to about 220°F. In very bad cases, the bearings may be boiled in an emulsifying solution of grinding or cutting compounds diluted with water. In such cases, the bearings must be thor- oughly drained and spun until all moisture has evaporated, then immediately washed in clean petroleum solvent or kerosene by revolving them slowly by hand and gradually working up to spinning speed. Care should be taken that all solid particles are removed, by a brush if necessary, before turning or spinning the bearing. After the bearings have been thoroughly cleaned, spin them in clean, new light o11 until the solvent has been completely removed. Relubricate the bearings 3-49