HOUSINGS

Steel and cast iron provide good surfaces for both rubber covered and metal O.D. seals.  For soft alloy (aluminum) bores, rubber covered O.D. seals provide better sealing capability.  In aluminum or other soft alloy bores, metal thermal expansionn of the soft alloy.  Rubber, having a higher coefficient of thermal expansion than carbon steel, will tighten in the bores as temperature rises.  Plastic or nylon are not recommended because they typically expand at a high rate causing a major problem for metal O.D. seals.  If plastic is to be used, rubber O.D. seals are recommended.

BORE CHAMFER

A bore chamfer is necessary to assist in installation of the seal.  To the right is the recommended configuration for the chamfer.

Proper chamfer angle and depth minimizes cocking of lack of squareness of the seal to the shaft, distortion of the seal cases, and reduces assembly force.

Recommended Bore Chamfer

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

The rubber O.D. seal is capable of functioning with a rougher finish.