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【正文】 t 900HV, although in many mechanisms special races are not provided and the interacting surfaces are hardened to about 600 HV. It is not surprising that, owing to the high stresses involved, a predominant form of failure should be metal fatigue, and a good deal of work is currently in progress intended to improve the reliability of this type of bearing. Design can be 5 based on accepted values of life and it is general practice in the bearing industry to define the load capacity of the bearing as that value below which 90 percent of a batch will exceed a lift of anew million revolutions. Notwithstanding the fact that responsibility for the basic design of ball and roller bearings rests with the bearing manufacturer, the machine designer must form a correct appreciation of the duty to be performed by the bearing and be concerned not only with bearing selection but with the conditions for correct installation. The fit of the bearing races onto the shaft or onto the housings is of critical importance because of their bined effect on the internal clearance of the bearing as well as preserving the desired degree of interference fit. Inadequate interference can induce serious trouble from fretting corrosion. The inner race is frequently located axially by abutting against a shoulder. A radius at this point is essential for the avoidance of stress concentration and ball races are provides with a radius or chamfer to allow space for this . Where life is not the determining factor in design, it is usual to determine maximum loading by the amount to which a bearing will deflect under load. Thus the concept of “static loadcarrying capacity” is understood to mean the load that can be applied to a bearing, which is either stationary or subject to slight swiveling motions, without impairing its running qualities for subsequent rotational motion. This has been 6 determined by practical experience as the load which when applied to a bearing result in a total deformation of the rolling element and raceway at any point of contact not exceeding percent of the rollingelement diameter. This would correspond to a permanent
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