INSTALLATION PRACTICES AND RETENTION METHODS
Press Fit Bearing Retention and Shaft Running Clearance
The standard method of sleeve bearing retention is a "press" or interference fit. The dimensional listing for thin wall Duralon bearings provides recommended housing bores that develop a press fit range of .0002" to .0022" on diameter.
The press fit range for heavy wall Duralon bearings is larger. Refer to the dimensional listing for recommended housing bores. To avoid shearing the bearing OD, the press fit should not exceed .008".
If the application will see large temperature variations, the differences in the coefficients of expansion of the bearing and the housing must be considered when determining the amount of interference fit required, especially if the housing is aluminum.
When determining shaft running clearance, one must take into account that the bearing bore diameter will be reduced an amount equal to the press fit between the bearing and housing. In other words, if your bearing press fit is .002”, your bearing ID will be reduced .002”. The following table lists recommended minimum shaft running clearances for catalog bearings.
| Recommended minimum shaft running clearances |
| Bore diameter (in.) |
Minimum diametral clearance (in.) |
| Up to .999 |
0.0005 |
| 1.000-1.999 |
0.001 |
| 2.000-2.999 |
0.002 |
| 3.000-3.999 |
0.003 |
| 4.000-4.999 |
0.004 |
| 5.000-5.999 |
0.005 |
| 6.000-6.999 |
0.006 |
| 7.000-7.999 |
0.007 |
| 8.000-8.999 |
0.008 |
| 9.000-9.999 |
0.009 |
| 10.000 |
0.010 |
| |
General bonding recommendations
Another popular bearing retention method is bonding the bearing into the housing. This method reduces the effect of tolerance buildup in the bearing ID after assembly, minimizing shaft and bearing clearance range. This method also improves concentricity between multiple bearings on one or more shafts. Epoxies give the highest bond shear strength. Any 2-part epoxy that will bond fiberglass to metal will work.
The housing I.D. and bearing O.D. must be free of contaminants - water, oil, grease, dirt, etc. When bonding, do not allow the ambient temperature to drop below 50°F and do not accelerate the curing process by heating the assembly up. Heat may cause the viscosity of the epoxy resin to drop, allowing it to run to one side of the bearing. This will reduce the bond strength. For proper bond thickness, allow .005" to .010" diametral clearance between the bearing O.D. and the housing I.D. Shafting can be used to align multiple bearings on one shaft while the adhesive cures.
Any bearing retention grade cyanoacrylate compound can also be used to retain Duralon bearings. Cyanoacrylates are used to enhance a light press fit or retain the bearing with a pure bond. Consult the adhesive supplier for the best recommendation to bond fiberglass to metal. The bearing OD may need to be primed prior to application of the cyanoacrylate to activate the bearing surface. The same primer used to prepare aluminum surfaces will usually work with Duralon bearings.
Consult Rexnord Engineering for special bearing retention or shaft clearance requirements. |
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