The Swiss Dr. Leeb first proposed a new hardness test method. The basic principle is that the impact body with a certain mass impacts the surface of the sample under a certain test force, and measures the impact velocity of the impact body at a distance of 1 mm from the surface of the sample. With the rebound speed, using the electromagnetic principle, the voltage is proportional to the speed. So which of the seven impact devices of the Leeb hardness tester are suitable for testing? The Leeb hardness value is expressed as the ratio of the rebound velocity of the impact body to the impact velocity. The impact device of the Leeb hardness tester has seven kinds of D, DC, D+15, C, G, E, and DL, respectively: D: Dimensions: f20*70mm, weight: 75g. General purpose, used for most Hardness measurement. DC: Dimensions: f20*86mm, weight: 50g. The impact device is short and is used primarily in very cramped areas such as holes or cylinders. D+15: Dimensions: f20*162mm, weight: 80g. The head is small and is used for surface hardness measurement of grooves or recesses. C: Dimensions: f20*141mm, weight: 75g. The impact energy is minimal, used to measure small light, thin parts and hardfacing layers. G: Dimensions: f30*254mm, weight: 250g. The impact energy is large and the measurement surface is required to be low. For forgings with large, heavy and rough surfaces. E: Dimensions: f20*162, weight 80g Indenter is synthetic diamond, used for the determination of extremely high hardness materials. DL: Dimensions: f20*202mm, Weight: 80g The head is finer and used for the measurement of the hardness of narrow grooves and gear faces.