In the process of purchasing bearings, equipment maintenance personnel in many factories will have their own methods of inspecting bearings. Some will check the printed paper and seals of the packaging, some will observe the workmanship of the chamfer, and others will observe the polishing of the bearing end face and the cylindrical surface. In the process of sales, they even encountered scraping the cylindrical surface with nails to judge the quality of bearings. Although these methods cannot fundamentally distinguish the advantages and disadvantages of bearings, But at least it can reflect the process and fineness of the bearing manufacturer in production. If it can't even meet the basic appearance requirements, in this era of fierce product competition, it can only be classified as a kind of product that strives for the market by cheap, and there is no way to demand quality at all.
Others have their own set of inspection methods. For example, when choosing a small deep groove ball bearing, they will rotate the bearing by hand and let the bearing idle. The bearing quality is judged by the length of time. Generally, this situation will think that the longer the bearing rotates, the better the quality. This behavior is not difficult to understand, because the bearing itself is a rotating part. Of course, the easier it turns, the better. But is this inspection method really practical? Or is there any scientific basis?
First of all, we need to explain that a long idle time does not mean that the bearing quality must be good. Because there are many factors that affect the idling time of bearings, including bearing clearance, grease, preloading and other conditions. Moreover, there is a great difference in the idling duration between sealed and unsealed, contact seal and non-contact seal, so the quality of the bearing can not be judged by turning it by hand.
