National/ Timken Seals Catalog - Norfolkbearings.com

SECTION 1-C TECHNICALSealing System Preparation And Seal InstallationBORE REQUIREMENTSMaintaining proper bore characteristics is important if the integrity of the sealing system is to remain intact. To provideproper fit of National Oil Seals, the dimensions relative to Bore Tolerance and seal Press Fit should be followed.Bore Tolerances and Seal Press FitThe Table below indicates recommended Bore Tolerances and seal Press Fit for both Metal and Rubber O.D. seals.Bore Bore Nominal Press Metal O.D. Nominal Press Rubber O.D.Diameter Tolerance Fit Metal O.D. Tolerance Fit Rubber O.D. ToleranceUp to 2.000 ± 0.001 0.005 ± 0.002 0.008 ± 0.0032.000 to 3.000 ± 0.001 0.005 +0.003 / -0.002 0.010 ± 0.0033.001 to 4.000 ± 0.0015 0.006 ± 0.003 0.011 ± 0.0034.001 to 5.000 ± 0.0015 0.006 ± 0.003 0.011 ± 0.0035.001 to 7.000 ± 0.0015 0.007 ± 0.003 0.012 ± 0.0047.001 to 12.000 ± 0.002 0.008 +0.004 / -0.003 0.013 ± 0.00412.001 to 20.000 ± 0.003 0.012 ± 0.005 0.015 ± 0.00520.001 to 40.000 ± 0.004 0.013 ± 0.005 0.018 ± 0.00640.001 to 60.000 ± 0.006 0.016 ± 0.006 0.020 ± 0.007Bore MaterialFerrous materials are commonly used for bore housings. The table above applies to these types of materials. However, ifother materials are used (i.e., aluminum or composites) higher rates of thermal expansion are usually involved andshould be considered.Bore FinishA finish of 125 microinches Ra (3.2 micrometers Ra) or smoother should be maintained to assure a leak free emvironment.If the bore is rougher than 125 microinches Ra (3.2 micrometers Ra) National Oil Seal offers an environmentally friendlywaterbase resinous coating on all of the O.D.’s of the metal cases. This coating process or material is termed Redicoat .BOREREDICOAT®OIL SEAL CASEBore ConfigurationThe lead corner of the seal bore should be chamfered for ease of seal installation. Rough corners or burrs can scratchthe seals outside diameter and cause potential leak paths..02 /.03 INCHTECHNICAL SECTIONREDICOAT IS A REGISTERED TRADEMARK OF FEDERAL-MOGUL CORP.XVII