While the tendency is to think only of gears made of ferrous metals, we find in Dudley^16 the statement: “A wide variety of bronzes, aluminum alloys, zinc alloys, and nonmetallic plastics and laminates are used to make gears.”
Fortunately, well refined mineral oils have little action on most of the combinations. We say combinations because in many cases the nonferrous gear is driven by a steel pinion, but when the loads are light and the gears are small, both members may be of the nonferrous material.
Nonreactive oils should be used with nonferrous gears unless specific recommendations state otherwise. This is illustrated in the case of worm gears where the gear is normally made of bronze. The general recommendation for such units is a mineral oil containing tallow, although often such oils contain lead soaps and occasionally certain EP agents.
Synthetic fluids, both diesters and “Ucon fluids, have been used as lubricants with nonferrous or ferrous and nonferrous combinations of gears. Where a problem of lubricating an unusual combination of gear materials is encountered, the manufacturer of the gear set should be able to make a safe recommendation. However, lacking a suggestion, a well refined lubricating oil with no reactive additives present can generally be used with safety in the case of nonferrous gear sets.
