Deep groove ball bearing hole system, minus tolerance is why? - bearing knowledge

From the deep groove ball bearings because this several days to buy a few bearing 6204. Rolling bearing branch of the following is the centripetal bearing, centripetal bearings include deep groove ball bearings or centripetal ball bearings. Base hole of the bearing inner hole size is minus tolerance. The following two paragraphs or taken from mechanical design manual: to prevent the bearing inner ring and shaft, outer ring and shell holes produce should not have the relative sliding when the machine is running, must choose the right fit. Usually axis and the inner ring with proper fit is to prevent shaft and the inner ring relative sliding of the most simple and effective method. Especially for thin wall ring bearing, using appropriate tight fit can make the bearing ring in sports uniform stress, and give full play to the bearing capacity. But with the bearing and can't be too tight, due to the elastic expansion of inner ring and outer ring contraction makes bearing radial clearance, reduce or even eliminate thus affect the normal operation. Bearing and shaft diameter d, base hole system, but the tolerance zone located below the zero line, the upper deviation is 0, compared with the general base hole system, in conjunction with the same name are more likely to get more close cooperation. Diameter D cooperate with shell hole of shaft basis, its tolerance zone is the same as general shaft basis, located below the zero line, the deviation is 0, but compared with the general tolerance system, its tolerance zone are not identical. Bearings with holes compared with shaft are loose. Add black is a complete sentence, can think the minus tolerance bearing base hole system is in order to obtain a close cooperation, in conjunction with the same name which cooperate with unapt too tight influence bearing function. So that can be achieved in the clearance fit with the same name or transition fit arrival interval, can reach the interference fit in the transition fit with the same name and not much interference in and affect the bearing operation. We seldom useful to figure 1 common rolling bearing the same name with the interference fit, generally in the clearance or interference of the same name with have a certain amount of interference. Same centripetal ball bearings of the tolerance zone is different from the general base hole system, the purpose is to fit for tight fit and not too tight. Ordinary level 0 bearings are usually not marking on bearings. Figure one for same with the bearing outer ring and the hole is also USES the basic shaft system, the basic shaft system and general, the deviation is 0, but the level 0 bearing tolerance zone is different from the general tolerance zone. As shown in figure 2, the level 0 6204 bearing outer ring size is 47, his lower deviation is 0. 009, relative to the smaller figure 3 h7, fit clearance is so small, also is the largest gap clearance fit quantity is small, which is with the same name will be tight. Figure 2 in figure 3