Hand-held power tools according to the protection of the electric shock can be divided into three categories Class I tools to prevent electric shock protection not only rely on the basic insulation, but also an additional safety measures, such as protective grounding, so that the conductive part can not be touched in the basic insulation damage will not become charged body. Class II tools to prevent electric shock protection not only rely on the basic insulation, but also includes additional security measures (but does not provide protective grounding or device-independent conditions), such as the use of double insulation or reinforced insulation. Its basic types are: â‘ Insulating material shell type, with a solid, substantially continuous insulation shell; â‘¡ Metal shell type, it has a basic continuous metal shell, all with double insulation, when the application of double insulation is not, then use Strengthen the insulation; â‘¢ insulation materials and metal shell combination type. Class III tools rely on safe extra-low voltage supply. The so-called security ultra-low voltage, refers to the phase line and the voltage between the ground does not exceed 42V, the safety isolation transformer. With the widespread use of hand-held power tools, the importance of electrical safety is even more prominent. The use of departments should be in accordance with national standards for hand-held electric tools to develop the appropriate safety practices. The content should include at least: the allowed range of use of the tool, the correct method of use, the procedure of operation, the part of the inspection site before use, the possible dangers in use and the corresponding protective measures, the storage and maintenance methods of tools, the operator should pay attention to Matters such as. In addition, the use, maintenance and repair personnel should also carry out safety technology education and training, pay attention to the inspection of hand-held power tools, the supervision of the use and maintenance, and the shockproof, dampproof and corrosion resistant. Before use, should choose the amount of hand-held power tools General workplace, class I tools should be used whenever possible. Class â… tools, should be equipped with leakage protector, isolation transformers and so on. In wet places should use â…¡ or â…¢ type of tools, such as the use of class â… tools, the operating current must be installed not more than 30μA, the action time of not more than 0.1s leakage protector. In boiler, metal container, pipeline operation, should use Class III tools, or with Class II leakage protection device, the leakage current protection device operating current is not greater than 15μA, action time is not greater than 0.1s. In special environments such as damp heat, rain and snow, the presence of explosive or corrosive gases and other operating environments, should be used with the appropriate level of protection and safety technology tools. Installation and use, Class III safety isolation transformer, Class II leakage protection device, â…¡, â…¢ type tool control box and power supply unit should be far away from the workplace. The power lead wire of the tool shall be made of tough rubber covered wire or plastic sheathed soft copper wire. There shall be no connector in the middle, and any length or disassembly shall not be allowed. Protective grounding resistance shall not be greater than 4Ω. Do not dismantle the protective cover of the running parts during the work, and replace the tool and abrasive tool to stop.