Radial oil seal

A feature of this seal is it’s short, but nevertheless, flexible lip and a stainless steel spring, on the shaft passage.This special design prevents the increase of the sealing lip contact pressure and consequently the frictional behavior. The seals are made for grease lubrication and can be used at peripheral speeds of up to 10 m/s even when housing without grease escape hole is used. The permissible angular misalignment for shaft diameter up to and including 100 mm is approximately 3°

The rubber material of the Oil Seal is much softer than the shaft, but due to friction between the shaft and the seal, it is possible for wear to occur on the contact surface of the shaft. The degree of wear depends on the structure of the shaft material. In general, the metal from which the shaft is made should have a homogeneous fine granulous structure and must have a minimum surface hardness of HRc 45. If the lubrication is doubtful, the medium is contaminated, dirt can enter from the outside and the speed of the shaft is more than 4 m/sec, the hardness of the shaft should be a minimum of HRc 55. In general, shafts of carbon steel or stainless steel are most suitable. Even more important than a correct interference fit of the Oil Seal is a perfectly smooth shaft in the region of the seal. The surface roughness of the shaft depends on the average profile depth Ra of the tool marks caused by the machining process.

For normal circumstances, the shaft in the region of the seal must have a surface roughness of approximately:

  • Ra = 0,4 – 0,8 mm
  • CLa = 8 tot 25 mm
  • Rz = 1,0 tot 4,0 mm and
  • Rmax ≤ 6,3 mm


To summarize, the surface of the shaft in the region of the seal should not have noticeable machining marks.

the oil seals are supplied in NBR (AS) or viton (SA) rubber,

Viton oil seals feature excellent resistance to petroleum products and solvents. They have good high temperature characteristics. They are suited for use with wide chemical exposure situations

The Radial AS seal can not be greased through the seal, the seal have to be used in combination of a CS seals or be used on places with clean water surrounding just to close and become a maintenance free bearing unit.


In some configurations, the bearing units from EXTREMEBEARING are pressure-tight! It is necessary that if you do the initial greasing, to keep the cap a little bit open. Otherwise, problems like in the picture can happen….

This bearing AS seals is damaged, because the cover is not loosened while greasing