Counter or Straight Bore
The bore type affects the positioning of the primary sealing lip and the O.D. sealability. A counter bore should be designed to control the position of the primary sealing lip. If the case has a nose gasket incorporated into the design, this gasket will provide additional O.D. sealing by forming a face seal. If the bore is straight, then a stopping mechanism needs to be included on the installation tool (See Installation Methods, page 64D) or a flanged case needs to be used.