Usually the periodic table having a  metal cutting wheel  luster, plasticity, good electrical and thermal conductivity of the chemical elements known metals. In the periodic table , there are 80 kinds of metal elements , other elements known as non-metallic . The classification is based on the history of metal formed on the industrial classification , this classification method, while not strictly scientific proof , it has not been used to the modern .
The most prominent feature is the metal of their tendency to lose electrons easily . Therefore, from a chemical point of view , the metal is easily formed in the solution of the chemical elements of positive ions , which combine with water to form the oxide hydroxide to form the corresponding acid instead . Metal between the difference in the chemical mainly in the electronic sequence , many chemical reactions , especially the oxidation -reduction reaction to determine the sign of the electrode potential and its magnitude .
From the physical point of view , since the metal atoms are contained in the outer layers or easily intensification of free electrons, and thus has a series of metallic ( metallic) .
In nature, most metals exist as compounds , few metals such as gold , platinum, silver, bismuth free state exists. Most of the metal oxide and sulphide minerals . Other existing forms of chlorides, sulfates, carbonates and silicates . The link between the metal is a metal key , so feel free to change position can re- create the link , which is a good reason for metallic stretch . Metal elements in the compound usually only noticeable price . The best ductility metal is gold (Au), good electrical conductivity at room temperature followed by silver (Ag), copper (Cu), aluminum (Al) , etc.

Cutting means with a metal cutting wheel  ( including cutting tools , grinding tools and abrasives ) of the blank or workpiece cut the excess material layer of a chip , provided to the workpiece geometry, dimensions and surface quality of the processing methods. Landlord wants to know is not the classification of cutting metal machining There are many classification methods . Common are the following three kinds . According to technical characteristics distinguish machining process characteristics depend on the structure of the cutting tool and the workpiece and the cutting tool relative movement form . Characterized by technology , machining can be divided into : turning, milling, drilling , boring , reaming , planing , slotting , broaching , sawing, grinding , grinding , honing , super finishing , polishing, gear processing, worm gear machining, threading , ultra- precision machining, fitter and scraping and so on. By removal rate and accuracy can be divided into : ① roughing : with a large depth of cut , the knife once or a few times to go from the workpiece cut most or all allowances , such as roughing , rough planing , rough milling , drilling and sawing , rough machining precision , high efficiency and low, generally used as pre- processing , and sometimes also for final processing . ② Semi-finishing : generally used as an intermediate between roughing and finishing step , but the workpiece demanding accuracy and surface roughness of the site, can be used as final machining . ③ finishing : cutting with a fine way to make the machined surface to achieve high accuracy and surface quality, such as fine cars, fine planing , precision reaming, grinding and so on. Finishing is the final process generally .