Precautions for using Rockwell hardness tester

(1) Regularly inject a small amount of engine oil into the contact surface between the screw and the handwheel.
(2) Before using the hardness tester, the top surface of the screw and the top surface of the workbench should be wiped clean.
(3) Regularly check the accuracy of the hardness tester with a standard hardness block. Testing on the supporting surface is never allowed.
(4) When there are burrs on the supporting surface of the standard hard block, it should be polished with a whetstone. When testing at different positions, the hard block should be dragged on the workbench and should not be taken away from the workbench.