【正文】 the bearing industry to define the load capacity of the bearing as that value below which 90 percent of a batch will exceed a life of one 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 withy bearing selection but with the conditions for correct installation.The fit of the bearing races onto the shaft or onto the housings is 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 provided 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 determined by practical experience as the load which when applied to bearing results 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 deformation of for a ball 25mm in diameter.The successful functioning of many bearings depends upon providing them with adequate protection against their environment, and in some circumstances the environment must be protected from lubricants or products of deterioration of the bearing surfaces. Achievement of the correct functioning of seals is an essential part of the bearing design. Moreover, seals which are appropriate bearing theory. Notwithstanding their importance, the amount of research effort that has been devoted to the understanding of the behavior of seals has been small when pared with that devoted to other aspects of bearing technology. The first is: bearing radial clearance is not adjustable spindle structure Before spindle bearing out the use of one pairs of cylindrical roller bearings and thrust ball bearing bination of both, the main use of double row cylindrical roller bearings under radial cutting force, the use of two ball bearings to bear axial thrust cutting force. After the general adoption of the spindle bearings out one pairs of cylindrical roller bearings or a ball bearing to the heart. Main advantages of this structure: the main axis of the processing and assembly of simple, low cost. One disadvantage: because the main axis of the radial bearing clearance can not be adjusted so poor precision spindle. Although the use of bearings and shaft diameter fit to eliminate the radial bearing clearance, but each bearing diameter and radial clearance is not a fixed value, so it is difficult to design and processing to the quasiaxialradial and bearings with bore tolerances. 2 disadvantage: it is very difficult to buy in the market of domestically produced or imported, C, D or P4, P5 class thrust ball bearings, machine tool manufacturing plant monly used alternative to the use of ordinary class bearings, which also affected the accuracy of the enhance spindle. Bearing radial clearance adjustable spindle structure do not apply to the general accuracy of the general machine tools, does not apply to require a higher accuracy of the spindle of machine tools. The second: the radial bearing clearance adjustable spindle structure Before the adoption of a spindle bearing P4 class of double row tapered hole cylindrical roller bearings and a P4class double row ball bearing thrust to the bination of heart. The use of the spindle hole of the double row tapered cylindrical roller bearings under radial cutting force, the use of double row ball bearing thrust to the heart to bear part of the axial and radial cutting force cutting force. Spindle bearings generally used after a P5 class of double row tapered hole cylindrical roller bearings. Double row tapered hole cylindrical roller bearings with inner ring and shaft are tapered 1:12, bearing lock nut with a round led a bearing in the axial displacement of the inner ring bearings and expansion, to reduce or eliminate Bearing radial clearance purposes. Main structure of such advantages: high precision spindle. At the front spindle diameter φ230mm noodle on the end measuring spindle Beat value of . Φ230mm cylindrical spindle at the front end on the radial axis measurement value of Beat . The second structure of the spindle of a precision spindle accuracy than the first about 50% improve. Main disadvantage of this structure: The principal axis of the more plicated process, the spindle assembly also has the experience necessary to make the workers to operate the spindle achieve the desired numerical accuracy.Ball bearings are used in almost every kind of machine and device with rotating parts. However, such bearings cannot be used indiscriminately without a careful study of the loads and operating conditions. In addition, the bearing must be provided with adequate mounting, lubrication, and sealing.A ball bearing usually consists of four parts: an inner ring, an outer ring, the balls, and the cage or separator. To increase the contact area and permit larger loads to be carried, the balls run in curvilinear grooves of the ball and a very slight amount of radial play must be provided. The bearing is thus permitted to adjust itself to small amounts of angular misalignment in the assembled shaft and mountin