bringing the cone into closer engagement. This will cause the balls to ride on the sharp edges of the grooves as shown at Fig. 401, B, which will result in rapid destruction of the entire bearing, because either a broken ball or some of the flaked particles of steel will get between the bearing parts. When adjustable bearings be

Fig. 402.-Wheel Removed from Motor Truck Front Axle to Show
Arrangement of Bearings on Steering Spindle.

come worn it is necessary to replace both worn cup and cone as well as entire new series of steel balls.

When it is necessary to replace a bearing the old one must be removed, and while a number of tools has been described that work very well on modern cars, some difficulty will be experienced

on those of early design because no provision was made for easy removal as is now the case. The easiest method of removing a bearing cone when it is forced on a wheel spindle and no opportunity is present for using a special puller is shown at Fig. 401, C. A sharp cold chisel is used, this being driven between the cone and the shoulder against which it is forced on alternate sides, first above, then below, and then on either side until the cone has been worked off of the wheel spindle. Similarly a ball or roller bearing cup that is a tight fit in a wheel hub may be driven out by careful application of a brass drift as shown at Fig. 401, F. The hammer blows should never be directed at any one point of the cup because if the pressure is applied at one point only it will cramp the cup in the hub and any further hammering after the cup is "cocked" will only serve to make it more difficult to remove. The method of removing a cone from a long shaft by a piece of pipe as at B, and by a gear puller as at Fig. 401, E, is generally understood by repairmen. If the cone resists either of these methods, it can be forced off under an arbor press.

Lubrication and Enclosure.-Ball bearings do not require the continual application of lubricants that is called for by plain bushings, and, to a lesser degree, by roller bearings, but this does not mean that lubrication can be neglected or done carelessly. The important point to observe is that none but pure mineral oils or greases be used, as any that show traces of acid or alkali, or that may become rancid from oxidization will cause etching and roughening of the highly finished surfaces of the balls and races. Lubricants best adapted range from light machinery oils, used in small high speed bearings, such as fitted in magnetos, lighting generators or starting motors, to the viscous grease utilized in those subjected to heavy loads and revolving at low speeds as wheel bearings or differential bearings. Wherever the bearing can be immersed in a bath of oil and properly protected from water and grit a lighter oil can be used, but when the bearings are housed where. dirt or water may get in, then the use of ample quantities of viscous lubricant, such as vaseline or other mineral grease that is free from acid prevents the foreign matter working in between the balls and races. Ball or roller bearings are generally enclosed in

such a manner that there will be no opportunity for dust, grit or water to enter, and if this function is properly performed the closure will also be tight enough to prevent escape of oil.

Importance of Proper Maintenance Emphasized.-Despite the extreme care taken in manufacture, bearings of the leading makes sometimes fail in service, and the motorist or average dealer, ever ready to condemn that which he does not fully understand, attrib

Fig. 403.-Wheel Removed from Full Floating Axle of Motor Truck to Show Method of Ball Bearing Installation.

utes the cause of failure to careless workmanship or the use of poor materials on the part of the producer, whereas the trouble is often due to conditions which are entirely within the user's control. A ball bearing must have a certain amount of running clearance, but in the leading types this is much less than in a plain bearing, it being common practice to allow a radial freedom never greater than .001-inch. In connection with this, in single row radial bearings an axial freedom or end play of the inner race relative to the

outer is allowed, this varying with the size of the bearing between the extremes of .0005-inch to .005-inch for new bearings. Thus a properly made and installed ball bearing will not deteriorate in the accepted sense of the term as applied to plain boxes; that is, there will be no reduction of diameter or increase in bore. If there is an excessive amount of axial or radial motion the cause is admittance of some abrasive between the components of the bearing

Bearings, etc.

or by overloading. As is true of any bearing, the amount of wear will depend upon the cutting power of the grit, the pressure the bearings are subjected to, and the amount of time the foreign matter is between the working surfaces.

There are places where a certain amount of dirt and metallic particles are always present. For example, many cases of trouble in rear axle and transmission case bearings have been definitely traced to the presence of minute particles of metal ground off from

the gears, or sand loosened from the interior of the gear case or rear axle housing castings. In sliding gears, especially when operated by an inexperienced person, there is a constant clashing of the pinions in changing speed, which tends to loosen particles of metal from the teeth. These fall into the lubricant, and are churned around and often find their way into the ball races. The

Fig. 405.-Chart Showing Drive Fits for Ball Bearings, etc. rapid failure of the bearing is the inevitable consequence. The importance of proper mounting has been so firmly impressed upon the automobile manufacturers that but little trouble is caused from improper installation in cars of reputable makes. Hence we are forced to consider the user in many cases when analyzing causes of bearing failure.

There is a condition that is beyond the control of the manufacturers of either the bearings or the mechanism to which they are fitted, and that is the use of impure oils, and carelessness in washing the running gear and other parts of automobiles. Many