Which type of oil seal, either covered seal or metal O.D. seal, is recommended depends upon the material of housing. The following are our recommendations.:
Housing material fit for metal cased seals - steel and cast iron.

When applied to housing material of high thermal expansion, such as aluminum or other soft alloys, at temperature raising condition, metal cased seals occasionally back out of the bore due to expansion clearness. On the other hand, if we use rubber covered seals instead of metal cased ones, the clearness will vanish because of the higher thermal expansion rate of rubber itself.

BORE CHAMFER

To assist in installation of seals, a bore chamfer is necessary. If the bore chamfer is improper or not existing, it will distort the seal case and require more assembly force.

SURFACE ROUGHNESS

Excessively rough bore finishes may allow paths for fluid to leak between seal O.D. and bore. Following is recommended maximum roughness.

SHAFT TOLERANCE
The tolerance range should be decreased for high speed or pressure applications.