When a bearing operates under load, heat is generated internally as a result of rolling, sliding and fluid friction. As the bearing speed increases, the temperature of bearing also increases. If the speed goes too high, bearing temperature would exceed certain limits, the efficiency of the lubricant would fall drastically and the bearing will no longer operate in a stable manner.

In order to control temperature rise at high speed, HCH technology center successively did experiments and research on dozens of grease that are provided by world famous oil manufacturers, finally decided a few of imported grease that are most suitable for electric power tools characteristics and requirements. Their com- prehensive performance at high speed is very good, especially for lower temperature rise and better life performance. General people only measure the temperature of bearing outside diameter, which is unscientific. As shown below, bearing surface temperature is only 40°C, while the bearing internal and grease temperature has reached 130°C. HCH has taken the lead to treat bearing inside maximum temperature as a measure of the temperature indicator.