Sintered porous bearing specimens of bronze having various permeabilities were made using atomized prealloyed powders through compacting, sintering and sizing processes. In order to study relations between the sliding noise and the viscosity of lubricating oil, the specimens were impregnated with base oils having various viscosities, which have no additives yet. Then, to study relations between the sliding noise and the kinds of lubricating oil, the specimens were impregnated with various commercial lubricating oils; for example, spindle oils, mobil oils and turbine oils etc. After the oil-impregnation, the sliding noise was measured with a testing apparatus, which was composed of a driving equipment and a sound analyzing equipment.
The results obtained were as follows; With the decrease of permeability from about 60 x 10^-3 darcy to (2-6) × 10^-3 darcy and with the increase of viscosity of base oil, the sliding noise in either case decreased gradually. However, the difference in sliding noise among various kinds of commercial lubricating oils could not be recognized clearly, excepting the effect of viscosity. That is, only the effect of viscosity of lubricating oils was thought to be remarkable to the sliding noise.
As a result, the cause will be able to be explained by considering both effects of the permeability of bearings and the viscosity of lubricating oils upon the mechanism of self-lubrication of sintered porous bearings.