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.
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.
National standard of vibration acceleration (commonly known as Z-standard)
The standard was established earlier, to measure the vibration acceleration value of the bearing when rotating, to determine the quality of the bearing, divided into Z1, Z2, Z3 from low to high quality grade. At present, bearing manufacturers in China are still using the vibration acceleration value to measure the advantages and disadvantages of the bearing, it simply reflects the fatigue life of the bearing.
Vibration velocity standard (commonly known as V standard)
Because the original vibration acceleration standard has not been abolished, so the standard is issued by the ministry of machinery industry standards, is the reference to the European standards combined with the actual situation and needs of our country, to test the bearing vibration speed to determine the quality of the bearing grade (equivalent to the national standard). Divided into V, V1, V2, V3, V4 five quality levels. Various ball bearing quality classes from low to high V, V1, V2, V3, V4; Roll bearings (cylinder, cone) quality grade from low to high for V, V1, V2, V3 four quality grade.
It is used to detect the vibration b velocity of bearing at different frequency segments (low frequency, medium frequency and high frequency) to reflect the bearing quality. It can be generally analyzed whether the bearing has the geometric size problem (such as the steel ring ellipse), the quality problem of raceway/rolling body, the quality problem of the cage, compared with the vibration acceleration to investigate the bearing quality has made a significant improvement. At present, the domestic bearings exported to Europe, the Chinese military and the aerospace industry all carry out bearing quality inspection in accordance with this standard, and at the same time, the quality inspection of European imported bearings and the discrimination of counterfeit imported bearings provide a feasible means.
There are two parallel standards in the bearing quality detection, and the bearings with high quality grade of "z-standard" may not have good quality performance when tested with "v-standard", and there is no correspondence between the two. This in the bearing quality inspection is to pay special attention to.