The working principle of the Leeb hardness tester is that the ratio of the rebound speed to the impact speed is converted into a digital signal by an electromagnetic induction coil to reflect the hardness value. When the workpiece is impacted, the elastic modulus changes due to the small workpiece or the workpiece is not stable, which may result in failure to display or low hardness. It proves that the elasticity has been lost, and the rebound force is absorbed by the workpiece. It mainly occurs on measuring hollow parts, thin plates and softer metal materials. Several methods for reducing the error are provided below: 1. For hollow materials such as pipes, try not to hit the cross surface, impact the end face, or add support in the pipe wall. Difficult but effective. Measuring curved surface diameter 20mm-100mm need to choose curved support ring; 2. For thin plate thickness should be more than 5mm (5mm below the workpiece, try not to choose the Leeb hardness tester), the measurement should be evenly spread on the back of the measurement butter in the platform and compact The coupling pushes the intermediate air out and is not movable. Do not apply too much butter; 3. Ensure the smoothness of metal materials, should be less than 7um in RA, the better the surface finish, so the hardness value is higher. 4. The solid core cylinder ensures the stability of the workpiece, and the small cylinder is the best. Add V-shaped table; 5. When measuring Brinell hardness, efforts should be made to improve the surface roughness, weight and coupling of the workpiece. If the surface roughness is poor and it is difficult to handle, in the case of a large workpiece, it is preferable to select a G-type impact device.