Allowable PV values is calculated and studied by the contact pressure P(MPa) and circumferential speed V(m/min) before using the oil-impregnated sintered bearing.

【Calculation method】

1. Calculation method of the contact pressure P ： P(Mpa)=Radial load (N)/{Bore diameter(mm)×Length(mm)}
2. Calculation method of the circumferential speed V ：　V(m/min)=Shaft diameter(mm)×π(circular constant)×Number of revolutions(min-1)×10-3
3. Calculation method of the PV value ：　PV value(Mpa･m/min)=P(Mpa)×V(m/min)

Generally recommended allowable PV values(Mpa･m/min)
Application	Allowable PV values
General-purpose machinery	100
Household appliances	50
Office electric appliances	50
Low noise and low wear applications	25
Especially low noise applications	20
Axial loaded applications	20

The life of the oil-impregnated sintered bearing is determined by the rate of consumption of the lubricating oil impregnated into the bearing.
Once 40% of the impregnated oil has been consumed, bearing performance deteriorates accordinaly.
In the case of a precisery small moter, severe noise and properties are required. So, the life is aimed by 30% of oil content.

Basic bearings’ lifetime