精度 TOLERANCE
轴承的精度包括尺寸精度和旋转精度,尺寸精度是将轴承安装于轴或轴承箱时所要求的项目,它包括内径、外径、宽度、倒角尺寸公差或允许值。几何精度包括内径偏差、平均内径差、外径偏差、平均外径差、套圈端面平行差的允许值。旋转精度是规定旋转时振摆的，包括内圈及外圈径向摆动和轴向摆动，内圈侧摆及外径面垂直度公差范围。
轴承的精度等级从普通级0级到6级、5级、4级及2级，依次增高，下表1是中国GB307规定的精度等级与其他标准的比较。
Bearing tolerance includes dimensional tolerance and revolving tolerance, Dimensional tolerance is a request when bearings are mounted on shafts or in housings. It includes bore/outerside diameter deviation from basic, inner ring/outer ring width deviation in single radial plane. Revolving tolerance includes radial and axial runout of assembled bearing inner ring and outer ring, inner ring reference fcace runout with bore and outside cylindrical surface runout with outer reference face.
Tolerance class ranges from common class 0 to 6,5,4 and 2, from low to high, Table 1 below is the tolerance class stipulated in China GB307 and its comparison with some other standards.

部分国家轴承精度等级对照表 COMPARISON OF TOLERANCE CLASS

游隙 CLEARANCE
轴承的游隙是指轴承在未安装于轴或轴承箱之前的状态下，固定内圈或外圈的一方，使未固定的套圈做径向或轴向移动时套圈的移动量。根据移动方向，可分为径向游隙和轴向游隙。
Bearing clearance means the value of displacement of the unfixed ring when it moves against the fixed ring in radial or axial direction before the bearing is mouted on a shaft or in a housing. According to the movement direction, it falls into radial clearance and axial clearance.

单列深沟球轴承的径向游隙 RADIAL CLEARANCE

振动 VIBRATION
轴承振动是指轴承零件随时间而变化的弹性变形及除轴承功能所必需的运动以外的其它一切偏离理论位置的运动,它分为振动速度(dB)和振动速度(μm/S)。振动动加速度分Ｚ、Ｚ１、Ｚ２和Ｚ３三级考核，其中Ｚ级为基本级，Ｚ１、Ｚ２和Ｚ３依次表示轴承振动水平有低到高，具体要求见表３。具体要求见表４。由于振动速度测量更能显现轴承的加工水平和体现轴承的内在质量，因而最为通用。
我们公司在对轴承振动速度值控制的同时，按电机轴承的要求，对轴承运转异声也实施严格的监控。
Bearing vibration means bearing components’ elastic deformation that varies with time and all other movement that deviates from a theoretic position except that necessary to bearing functions. It has two modes-acceleration(dB)and velocity(μm/S), Vibration acceleration is examined according to Z, Z4, Z2, and Z3 values. Grade Z is fundamental, Z1, Z2&Z3 successively indicate the vibration level ranges fron low to high. For detailed requirements, see Table3. Simlary, viaration velocity is examined as per V, V1, V2&V3. Grade V is fundamental, V1, V2&V3 successively indicate the vibration level ranges from low to high. For details, see Table4. Generally, velocity examination is better than acceleration examination in that it can more reflect bearings’ manufacturing level and bearings’ inherent quality.
While our company keeps control of vibration velocity values, we also carry out vigorous control on abnormal noise from running bearings in test according to requirements of electric motor quality bearings.

单个轴承振动加速度极限值　VIBRATION(ACCELERATION) LIMITES FOR SINGLE BEARING dB

单个轴承振动速度极限值 VIBRATION (VELOCITY)LIMTES FOR SINGLE BEARING μm/s