Standards of second-hand ball mill 
Ball mill main wear standards: 
1, bearing abrasion is greater than a third of its thickness. 
2, small gear surface erosion rate should not be greater than 30% of the tooth thickness, big ring gear tooth surface wear is greater than 25% of the tooth thickness, can use inverted face, grinding to 1/2 should be scrapped. 
3, the distortion deformation of gear ring flange should not be greater than 7.5 mm. 
4, hollow shaft surface groove, flecked or internal circular surface worn through to the hollow shaft deformation, cracks, and so on and so forth should be replaced.