When the hardness of the steel shot is greater, when cleaning the workpiece, its speed is very fast, but the consumption of the steel shot will also become very fast so that its service life will be shortened faster than the general time. So for the economic benefits from  workpiece cleaned up before are all can choose moderate hardness steel shot for processing work, correct selection of steel shot is the key to improve the work efficiency, steel shot high hardness, the workpiece cleaning effect is good, relative to the consumption of good, so, the use of steel shot, according to the workpiece material and hardness, to choose the appropriate steel shot, In this way, the service life of steel shot can be improved.