For purchasing channels, you can choose wholesale manufacturers online and offline, you can contact manufacturers or agents for purchasing. For example, First Linkage is an online hardware wholesaler. He represents many brands, such as Bosch, Metabo, Makita, Dongcheng and Bogesima. Of course you can also go there. websites for reference.
Power Tools:
In 1895, the German company Fein manufactured the world's first direct current electric drill. The housing is made of cast iron and can drill 4mm holes in the steel plate. Then a three-phase electric drill with industrial frequency (50 Hz) appeared, but the motor speed did not exceed 3000 rpm. In 1914, electric tools driven by single-phase series motors appeared, and the motor speed reached more than 10,000 rpm. In 1927, a medium-frequency power tool with a frequencye power supply from 150 to 200 Hz appeared. It not only had the advantages of high speed of single-phase series motors, but also had the simple structure of three-phase industrial frequency motors. .