be machined with equal accuracy and should be just enough smaller than the bearing bore so that inner race will be an easy push fit on the shaft. It is customary to always restrain the bearing inner race from movement by means of a clamp nut or its equivalent. These are depended on to force the inner race firmly against a shoulder or tubular spacing member on the shaft, as outlined at Fig. 245.

Q. How are anti-friction bearing outer races secured?

A. If a bearing is to resist end thrust as well as radial load it is customary to clamp the outer race between a threaded closure member and a shoulder in the housing as shown at Fig. 245. The closure member, however, does not bear against the bearing outer race but a space of about .01 inch is allowed between the bearing outer race and shoulders on clamp nut and housing. An outer race is invariably a free push fit in the housing. If the bearing is to be subjected to only a radial load it is not necessary to clamp the bearing outer race.

Q. Why is it desirable to clamp bearing inner race to shaft? A. The bearing inner races are clamped firmly to the shaft in order to prevent creeping of the inner race on the shaft under heavy loads as this would tend to wear the shaft and the bearing would not be held in place as firmly as it should be if the cone once started to turn around.

Q. When narrow single row bearings are to be housed in soft metal, what is a desirable precaution to take?

A. In order to prevent the narrow outer races, which are of hard steel, from peening the soft aluminum alloy of a gear case, for example, it is customary to house the outer races in a member of pressed steel, cast bronze or malleable iron which is firmly pressed into the soft metal case and which takes all the strain imposed on heavily loaded bearings.

Q. What is the best method of installing radial bearings when two are used on a shaft subjected to thrust?

A. Only one of the bearings should be employed to resist the +hrust load and this should have both inner and outer races clamped.

The other bearing which is depended on to take only radial loads has a "floating" outer race but a clamped inner member.

Q. In assembling adjustable ball or roller bearings what precaution is necessary?

A. It is imperative that the parts of the bearing be adjusted to a nicety. The adjusting nut should be screwed up only to such

Fig. 245.-Method of Mounting Ball Bearing Subjected to Radial and Thrust Loads.

a point that absolutely all the lost motion or radial play is taken from the member supported and yet that member should be free to revolve without friction. If the bearings are tightened up unduly they will wedge and bind and wear out quickly. If they are not adjusted tightly enough the balls or rolls will be subjected to a series of hammer-like blows whenever the bearing is operated and this will also produce rapid depreciation of the bearing.