Seal and shaft compatibility is dependent on four conditions: shaft tolerance, lead-in chamfer, finish and hardness.  Proper consideration of these conditions will assist in providing optimal seal performance.

SHAFT HARDNESS is an important factor to prevent excessive wear, deformation, scratches or nicks, and to allow for easy machining for proper roughness.  Under normal conditions, the seal contact area of the shaft should be Rockwell C45 minimum.

SHAFT SURFACE ROUGHNESS is very important as this greatly influences the amount of lip wear.  The recommended roughness is as follows:

- Rotating 10 to 20 µ inch R_a (.25 µM to .50 µM R_a): R_max = 31 - 126 µ inch (0.8 - 3.2 µM)

- Reciprocating 5 to 10 µ inch R_a (.13 µM to .25 µM R_a) The method of achieving this finish should not be overlooked.

PLUNGE GRINDING is recommended for rotating shaft applications.  For reciprocating applications, centerless grinding is acceptable.  Rotating shaft applications require a surface with no machine lead, as machine lead may actually pump fluid from under the seal lip.  Also, hard chrome plating is suggested for any cast iron or stainless steel shafts for rotating applications and for steel shafts with reciprocating applications.

A SHAFT CHAMFER is suggested to assist in the installation process.  Without a proper chamfer, the seal lip may be damaged or distorted resulting in a dislodged garter spring.

SHAFT TOLERANCE recommendations for general applications are listed below.  The tolerance range should be decreased for high speed or pressure applications.

Table 6

Recommended Shaft Chamfer

Recommended Shaft Tolerance