In last months Driving Old Cars, we began this three-part series on ball bearings, covering parts, types, and bearing removal This month, we will cover cleaning, inspection, and mounting.
When bearings are brought in to be cleaned, do not allow anyone to pick them up and spin them, as in Figure 1. A bearing which would otherwise be in entirely serviceable condition after cleaning, might be seriously damaged at this point by such practice. The importance of this lies in the fact that scratches that can be caused by spinning before cleaning may not be felt during inspection and the life of the bearings might be shortened by such injury.
Do not let dirt and oil accumulate in the place where bearings are laid previous to washing. Wipe this place frequently, then fairly clean used bearings cannot become laden with gritty oil from other bearings, as was the case in Figure 2.
Do not pile too many bearings at a time in basket for washing, Figure 3. Residue from very dirty bearings might wash down into other bearings below, thus requiring a longer time to wash than if fewer were cleaned at a time. Double row bearings usually require more time for washing and need more thorough flushing because of the greater width and number of places from which old lubricant or residue must be dislodged.
Bearings with seals or shields on both sides, Figure 4, should not be washed, but should be wiped reasonably clean on the outside and sent by themselves to inspection. The reason for this is that a large proportion of such bearings are clean enough inside when removed to be reused, but if immersed in a tank of cleaning fluid, dirt might be washed in and the fluid could not wholly be removed from the bearings.
Place bearings in a wire basket so there is plenty of space for cleaner to reach all parts and immerse in a cleaning solvent. The tank should have a screened false bottom to prevent settlings from being stirred up into the bearings.
Agitate the basket frequently until grease, oil or sludge is thoroughly loosened and can be flushed out.
Bearings that contain especially heavy carbon deposits or hardened grease should be put in a basket by themselves and soaked in a separate container of solvent. Be sure to use a carbon-softening fluid approved for bearing use.
Using a spray gun with air filter and clean solvent, flush each bearing as in Figure 7, until all dirt or residue is removed. Turn one of the races slowly while flushing to help dislodge dirt from around the balls and separator pockets.
With dry, filtered air, blow the solvent out of the bearings, being careful not to spin them by force of air. Since dry bearings rust quickly, lubricate them by dipping bearings in clean light spindle oil. Rotate them a few times, and after draining off the excess oil, place them in a covered container for inspection.
Most ball bearings fail from preventable causes. The bearing inspector can soon acquire a good knowledge of the causes behind the failures and can use this data to apply corrective measures at parts assembly to avoid repetition of the troubles.
Follow a regular system for inspection. Look for bearings with obvious or visual damage first. Discard bearings that show any of the following:
1. Rusted balls or raceways. Usually caused by water passing worn or defective seals or by condensation inside the housing (Figure 9)
2. Fractured ring. Forcing a cocked bearing on or off a shaft will do this, as will too heavy a press fit (Figure 10)
3. Worn, galled or abraded surfaces. Can be caused by too loose a fit, or bearing locked by dirt and turning on shaft or in housing (Figure 11)
4. Broken or bent shields, seals or separator. Usually caused by improper uses of tools during mounting or
removal (Figure 12)
5. Badly discolored balls and races. Usually due to inadequate supply of lubricant (Figure 13). Moderate
discoloration of balls and ball track is not a cause for discard.
Single row radial bearings, Figure 14, normally have a certain amount of looseness or endplay, which is easily felt when dismounted.
Single row angular contact bearings, Figure 15, are very loose when unmounted and this greater looseness should not be mistaken for wear.
Double row angular contact bearings, Figure 16, are usually made to zero or minus endplay and should have no endplay that can be distinguished by hand feel.
Bearings rotated by hand for internal inspection should be under enough axial pressure to bring balls and raceways firmly into contact. In case of single row angular contact bearing, pressure must always be applied on the thrust faces.
Bearings should be rejected for the following reasons:
1. General feeling of roughness which remains unchanged by thorough cleaning, indicating damage to raceways or balls, such as indenting by dirt or pitting by corrosion.
2. Catchy or rough feeling at one or more points which repeated flushing will not remove and which may be a spalled or fatigued spot as in Figure 17. Thorough flushing is necessary to be sure it is not caused by dirt.
3. Excessive looseness or endplay, indicating lapping by dirt or abrasive in lubricant as in Figure 18. If in doubt check against endplay feel of identical new bearing. Races and balls are dull gray when lapped by dirt.
4. Any looseness or endplay which can be detected by hand feel is a cause for rejection only in the case of double row angular contact bearings.
It's worth searching to find the right lubricant. We usually get our 90-weight and 140-weight gear oils at Napa. The multi-viscosity oils, in my opinion, just don t provide the same protection for our old car bearings that the straight weight mineral oils do. Enjoy your cars,see you next month with bearing mounting and front wheel bearings.
Keep 'em driving!