Lubricants used.in connection with Timken bearings must be of two distinct kinds, in that they have two distinct duties to perform, namely :-(1) They must protect the bearing. (2) They must lubricate the bearing.

When a bearing is functioning at comparatively slow speeds as in the road wheels of motor vehicles, the actual lubricating value of the lubricant is of secondary consideration, its main purpose being to protect the bearing from moisture and grit.

When, however, a bearing is being used in conjunction with gears as in the differential housing or the transmission, the lubricant must then, in addition to providing protection against moisture and grit, provide lubrication for the gearing, and on account of the higher speed, more perfect lubrication for the bearing than is necessary in road wheels.

Road Wheel Lubrication

As has been stated, the main purpose of a lubricant in road wheels is to protect the bearing surfaces from the effects of moisture and grit, and this is best obtained by filling the hub entirely with a medium body grease which is free from acid and moisture, and which is of such a consistency that in service the grease will flow to the working parts of the bearing.

Smearing of the rollers of the bearing is generally insufficient in that moisture and grit are not prevented from entering the hubs, should the enclosure be in any way defective.

When re-lubricating road wheel bearings, which should not be necessary more often than twice a year, the old grease should be removed, the bearings and hubs thoroughly cleaned, and the dust washer replaced if badly worn. The hub cap, as well as the hub, should be filled with grease owing to the tendency in front wheels for the grease to work towards the outer end of the hub.

Rear-Axle And Transmission Lubrication

The lubricant of the differential and pinion, and in the same way of the transmission must, as has been seen, provide effective lubrication for the gears and the bearings. On account of the high speed, grease is entirely unsuitable for this, and experience shows that a mineral oil of rather high viscosity, which is free from acid, gives the best results. Graphites should be avoided owing to their tendency to clog the passages leading to the bearings.

When re-lubricating rear axles and transmission, all old oil should be drained away and the housing thoroughly washed out with paraffin. Fresh lubricant should then be introduced up to the level designated by the oil filler plug in the housing. Such lubrication is necessary about twice a year and for ease of starting a rather lighter lubricant should be used in the winter than in the summer.

These tapered roller bearings are applicable for very many industrial machine purposes, but space does not permit dealing with such here, the above, however, describes the general principle and design.