The Rockwell hardness tester is also called Rockwell hardness machine. The Rockwell hardness standard of China is 150 kg. The hardness of the C scale is the diamond cone with the apex angle of 120 degrees. The test load is a certain value. The hardness tester is used to test the hardness of sheet metal, thin-walled pipe, case hardened steel and small parts. Because of the small test force, the indentation is also small, especially the surface Rockwell hardness test has smaller indentation, for most workpieces. The use of no influence can directly test the finished workpiece. The initial test force is used, so that the slight unevenness of the sample surface has less influence on the hardness value. Therefore, the instrument is very suitable for use in the factory and is suitable for batch processing. Finished or semi-finished workpieces are tested piece by piece. This test method has low requirements for measurement operations and is easy for non-professionals to master. Rockwell hardness test uses 3 kinds of indenters, 6 kinds of test force, according to the material of metal material, hardness range and size, there are 15 rulers to choose from, which can be tested from very soft to very hard. The metal material has a wide range of applications. Rockwell hardness testers have been widely used in industrial production, and become the main means to verify product quality and determine reasonable processing technology. It can test various black and non-ferrous metals and test the hardness of hardened steel, case hardened steel, annealed steel, tempered steel, various thickness plates, cemented carbide materials, powder metallurgy materials, and thermal spray coatings. When the measured object HB is greater than 450, the Brinell hardness test cannot be used instead of the Rockwell hardness measurement. The Rockwell hardness tester uses a diamond cone with a apex angle of 120° or a steel ball with a diameter of 1.59 and 3.18 mm. The probe is pressed into the surface of the material to be tested under a certain load, and the hardness of the material is determined from the depth of the indentation. According to the hardness of the test material, it is expressed in three different scales: HRA: is the hardness obtained by using 60kg load and diamond cone presser, and is used for extremely hard materials such as cemented carbide. HRB: It is a hardened steel ball with a load of 100kg and a diameter of 1.58mm. The hardness is used for materials with lower hardness such as annealed steel and cast iron. HRC: is the hardness obtained by using a 150kg load and a diamond cone indenter for materials with high hardness (such as hardened steel).