OIL SEALS
Oil seals prevent internal system fluids from leaking and keep external contamination from entering the system. Leakage and/ or contaminants paths occur between the shaft and the seal lip and between the seal and the housing. Oil seals need to seal both dynamically (on the shaft) and statically (on the outer diameter of the seal).
An oil seal normally consists of three basic components: the rubber sealing element, the metal insert (case) and the garter spring. The purpose of the sealing element is to stop the fluid from leaking between the shaft and housing. The metal insert will give rigidity and strength to the seal while it is being held in the bore or recessed groove. The garter spring will help make the rubber sealing element more effective.
Where hydrodynamic aids have been provided it should be remembered that a pressure deficit can be produced in the space between primary and secondary lips which will increase the radial force. This situation can be alleviated by providing breathing holes in the secondary lip. It should also be remembered that contaminants which have penetrated past the secondary lip will eventually cause damage in the couterface region. A build-up of heat can also occur between the two lips; this promotes premature wear.

ORDER REFERENCE CHART FOR OIL SEALS

Use the oil seal reference chart when ordering.
SEAL O.D. TOLERANCE - METRIC
Press-fit Allowance | |||
Bore Diameter (mm) | Metal Case | Rubber Covered Case | Permissible Eccentricity |
Up to 50 | +0.10 – +0.20 | +0.15 – +0.30 | 0.250 |
Over 50 to 80 | +0.13- +0.23 | +0.20- +0.35 | 0.350 |
Over 80 to 120 | +0.15- +0.25 | +0.20- +0.35 | 0.500 |
Over 120 to 180 | +0.18- +0.28 | +0.25- +0.45 | 0.650 |
Over 180 to 300 | +0.20- +0.30 | +0.25- +0.45 | 0.800 |
Over 300 to 500 | +0.23- +0.35 | +0.30- +0.55 | 1.000 |
HOUSING & SHAFT TOLERANCE - METRIC
House Tolerance | Shaft Tolerance | ||
Bore Diameter (mm) | Bore Tolerance | Shaft Diameter (mm) | Tolerance |
Over 6 to 10 | +0.022/-0.000 | Over 3 to 6 | 0/-0.075 |
Over 10 to 18 | +0.027/-0.000 | Over 6 to 10 | 0/-0.090 |
Over 18 to 30 | +0.033/-0.000 | Over 10 to 18 | 0/-0.110 |
Over 30 to 50 | +0.039/-0.000 | Over 18 to 30 | 0/-0.130 |
Over 50 to 80 | +0.046/-0.000 | Over 30 to 50 | 0/-0.160 |
Over 80 to 120 | +0.054/-0.000 | Over 50 to 80 | 0/-0.190 |
Over 120 to 180 | +0.063/-0.000 | Over 80 to 120 | 0/-0.220 |
Over 180 to 250 | +0.072/-0.000 | Over 120 to 180 | 0/-0.250 |
Over 250 to 315 | +0.081/-0.000 | Over 180 to 250 | 0/-0.290 |
Over 315 to 400 | +0.089/-0.000 | Over 250 to 315 | 0/-0.320 |
Over 400 to 500 | +0.097/-0.000 | Over 315 to 400 | 0/-0.360 |
HOUSING TOLERANCES - INCH
Diameter (in) | Tolerance |
Up to and including 4.000 | +/-0.003 |
4.001 to 6.000 | +/-0.004 |
6.001 to 10.000 | +/-0.005 |
10.0001 and larger | +/-0.006 |
SEAL O.D. TOLERANCE - INCH
Press-fit Allowance | Bore Tolerance | |||
Bore Diameter (in) | Metal Case | Rubber Case | Metal Case | Rubber Case |
Up to 1.000 | +0.004 | +0.006 | +/-0.002 | +/-0.003 |
1.001 to 2.000 | +0.004 | +0.007 | +/-0.002 | +/-0.003 |
2.001 to 3.000 | +0.004 | +0.008 | +/-0.002 | +/-0.003 |
3.001 to 4.000 | +0.005 | +0.010 | +/-0.002 | +/-0.004 |
4.001 to 6.000 | +0.005 | +0.010 | +0.003/-0.002 | +/-0.004 |
6.001 to 8.000 | +0.006 | +0.010 | +0.003/-0.002 | +/-0.004 |
8.001 to 10.000 | +0.008 | +0.010 | +0.004/-0.002 | +/-0.004 |
10.001 to 20.000 | +0.008 | +0.010 | +0.006/-0.002 | +/-0.004 |
20.001 to 40.000 | +0.008 | +0.010 | +0.008/-0.002 | +/-0.004 |