... other word.3,Gear shaft:The material is 45#steel,with furface carburization treatment for high strength and wear-resistance. 4 ... ,Spring:Adopts quality spring steel,with less than 1mm shortening afer 300,000times squeezing.At door ... produce door closing force to close the door. 5,Swing arm:The matetial is cold-rolled sheet,its main function is ...