The main purpose of bearing lubrication is to form a lubricating oil film on the friction surface between the ferrule,the rolling element and the cage to reduce the friction and wear of the bearing and prevent sintering,thereby prolonging the service life of the bearing.In addition,the lubricant also acts to prevent bearing corrosion,reduce vibration noise,cool down,and prevent foreign matter from entering.

　　First,grease lubrication

　　Grease lubrication is the most common lubrication method for bearings because of its ease of use and simple maintenance.

　　The most commonly used grease for rolling bearings is lithium-based grease with mineral oil as the base oil.The grease has good adhesion and good lubrication in a wide temperature range and speed range.The applicable temperature range is-30°C~+110°C.For high-speed precision spindle bearings,synthetic bismuth grease or calcium-based grease based on synthetic double-fat lubricating oil can also be used.The consistency should be 2nd.

　　Grease-lubricated bearings must be advanced in the early stage of work.After running,excessive grease is forced into the bearing raceway to evenly distribute the grease inside the bearing,and the heat balance temperature is guaranteed to be the lowest when the bearing is working normally.

　　The normal running step is to gradually increase the speed in stages,and each stage must wait until the temperature of the bearing is stable before moving to the next stage.If the stage is too much or the limit speed of the bearing is high,the running time will be longer.The running can start from 20%to 25%of the limit speed.When the steady temperature is reached,increase the speed until the limit speed of the bearing is reached and the temperature is stable.It is important to note that during the running-in process,the temperature of the bearing should be monitored at all times and,if possible,the temperature of the outer ring of the bearing can be monitored directly.When the temperature exceeds 60°C,stop it.When the temperature drops by about 10°C,restart at the same speed until the end of the run.

　　Second,oil lubrication

　　When grease lubrication cannot meet the requirements of high speed performance of the machine,oil lubrication can be used.The most commonly used oil lubrication for machine tool spindle bearings is oil mist lubrication,oil and gas lubrication,and fuel injection lubrication.

　　1,oil mist lubrication

　　(1)Advantages:Due to the continuous injection of new lubricating oil,oil deterioration does not occur;dust and cutting fluid are not easily invaded.

　　(2)Disadvantages:Oil mist pollutes the environment;oil flow rate depends on the viscosity and temperature of the oil,and it is difficult to control the small flow rate;it is difficult to determine the actual oil supply.

　　2,oil and gas lubrication

　　(1)Advantages:The optimal oil quantity can be controlled,the bearing heat is low;the cooling effect is good,the temperature rise is low;the dust and the cutting fluid are not easy to invade;and the environment is hardly polluted.

　　(2)Disadvantages:The cost of the lubricating device is slightly higher;the actual oil supply of the bearing is still difficult to determine.

　　3,injection lubrication

　　(1)Advantages:Due to the large flow,dust and cutting fluid will not enter the bearing and will not burn the bearing;the fuel will take away heat and the bearing temperature rise can be controlled.

　　(2)Disadvantages:large friction loss;due to oil leakage,the spindle should not be installed vertically;the lubrication device is costly.