There are many varieties of machine tool parts, which can be divided into: shaft parts, gear parts, machine tool guide rails, etc. according to their structural characteristics, functions and load characteristics.

Material selection of machine tool shaft parts

The machine tool spindle is the most important shaft part in the machine tool. Different types of machine tools have different working conditions of the spindle. According to the size and type of the load on the spindle when it is working, it can be roughly divided into four categories: (1) Light-load spindle. The working load is small, the impact load is not large, and the wear of the journal is not serious, such as the spindle of a common lathe. This type of shaft is generally made of 45 steel, which has been quenched and tempered or normalized, and is strengthened by high-frequency surface quenching in the parts that require wear resistance. (2) Medium load spindle. Moderate load, serious wear and certain impact load, such as milling machine spindle. Generally made of alloy quenched and tempered steel, such as 40Cr steel, after quenching and tempering treatment, the wear-resistant parts are required to be surface quenched and strengthened. (3) Overload the spindle. The working load is large, and the wear and impact are serious, such as the spindle of the combined machine tool with a large working load. Generally made of 20CrMnTi steel, carburized and quenched. (4) High precision spindle. The working load of some machine tool spindles is not large, but the precision requirements are very high, and the deformation after heat treatment should be extremely small. Wear should be minimal during work, such as the spindle of a precision boring machine. Generally, it is made of 38CrMoAlA special nitrided steel. After quenching and tempering treatment, it is subjected to nitriding and dimensional stabilization treatment. In the past, spindles were almost entirely made of steel, and light-duty and medium-duty spindles are already available in ductile iron.

Material selection of machine tool gear parts

Machine tool gears are divided into three categories according to working conditions:

(1) Light load gear. The rotation speed is generally not high, and most of them are made of 45 steel, which has been normalized or quenched and tempered.

(2) Medium load gear. Generally made of 45 steel, after normalizing or quenching and tempering, high-frequency surface quenching is carried out to improve the bearing capacity and wear resistance of the gear. For large-sized gears, it is necessary to use alloy quenched and tempered steel such as 40Cr. Most of the gears in the transmission system and feed system of general machine tools belong to this category.

(3) Heavy duty gear. For some gears with large working loads, especially gears with high operating speeds and large impact loads, most of them are made of carburized steels such as 20Cr and 20CrMnTi. It is used after carburizing and quenching. For example: some important transmission gears in the gearbox, etc.

Selection of machine tool guide rails

The accuracy of the machine tool guideway has a great influence on the accuracy of the entire machine tool. It must be prevented from deformation and wear, so the guide rails of machine tools are usually made of gray cast iron, such as HT200 and HT350. Gray cast iron has good wear resistance under lubricated conditions, but has poor resistance to abrasive wear. In order to improve wear resistance, the surface of the guide rail can be quenched. ​