Machining method of boring

Bore a hole

Boring is a machining method in which the prefabricated hole is enlarged with a cutting tool. The boring work can be carried out either on the boring machine or on the lathe.

1. Boring method

There are three different machining methods for boring. (1) Workpiece rotation, cutting tool for feed movement on the lathe boring mostly belongs to this boring mode. The characteristics of the process are: the axis line of the hole after processing is consistent with the rotation axis of the workpiece, the roundness of the hole mainly depends on the rotation accuracy of the machine tool spindle, and the axial geometry error of the hole mainly depends on the position accuracy of the tool feed direction relative to the rotation axis of the workpiece. This boring method is suitable for machining holes with coaxial requirements on the surface of the outer circle.

(2) Tool rotation, workpiece feed movement boring machine spindle drive boring tool rotation, table drive workpiece feed movement.

(3) The tool rotates and makes the feed movement using this boring method boring, the overhang length of the boring bar is changed, the force deformation of the boring bar is also changed, the aperture near the headstock is large, the aperture away from the headstock is small, forming a cone hole. In addition, with the increase of the overhang length of the boring bar, the bending deformation of the main shaft caused by its own weight also increases, and the axis of the machined hole will have a corresponding bending. This boring method is only suitable for machining short holes.

2. Diamond boring

Compared with general boring, diamond boring is characterized by a small amount of back cutting, small feed, high cutting speed, it can obtain a high processing accuracy (IT7 ~ IT6) and a very smooth surface (Ra is 0.4~ 0.05μm). Diamond boring was originally processed with diamond boring tools, and is now commonly processed with cemented carbide, CBN and artificial diamond tools. Mainly used for processing non-ferrous metal workpieces, can also be used for processing cast iron and steel parts.

The commonly used cutting parameters of diamond boring are: pre-boring of 0.2~0.6mm and final boring of 0.1mm; The feed rate is 0.01~0.14mm/r; The cutting speed is 100~250m/min when processing cast iron, 150~300m/min when processing steel, and 300~2000m/min when processing non-ferrous metals.

In order to ensure that the diamond boring machine can achieve high machining accuracy and surface quality, the machine tool (diamond boring machine) must have high geometric accuracy and stiffness, the main shaft of the machine tool supports the commonly used precision angular contact ball bearing or static pressure plain bearing, and the high-speed rotating parts must be accurately balanced; In addition, the movement of the feed mechanism must be very smooth to ensure that the table can do smooth low-speed feed movement.

The machining quality of diamond boring is good, the production efficiency is high, and it is widely used in the final processing of precision holes in a large number of mass production, such as the engine cylinder hole, the piston pin hole, the main shaft hole on the spindle box of the machine tool. However, it should be noted that when machining ferrous metal products with diamond boring, only the boring tool made of cemented carbide and CBN can be used, and the boring tool made of diamond can not be used, because the carbon atoms in diamond have a large affinity with the iron group elements, and the tool life is low.

3. Boring tool

Boring tool can be divided into single-edge boring tool and double-edge boring tool.

4. Boring process characteristics and application range

Compared with the drilling, expanding and reaming process, the bore size is not limited by the tool size, and the boring has a strong error correction ability, and the deviation error of the original hole axis can be corrected by multiple cutting, and the boring can maintain a higher position accuracy with the positioning surface.

Compared with the outer circle of the boring, due to the poor rigidity of the tool bar system, large deformation, poor heat dissipation and chip removal conditions, the hot deformation of the workpiece and the tool is relatively large, and the processing quality and production efficiency of the boring are not as high as the outer circle of the car.

In summary, it can be seen that the processing range of boring is wide, and holes of different sizes and different precision levels can be processed. For holes and hole systems with large aperture, high size and position accuracy requirements, boring is almost the only processing method. The machining accuracy of boring is IT9 ~ IT7. Boring can be carried out on the boring machine, lathe, milling machine and other machine tools, which has the advantages of flexibility and flexibility, and is widely used in production. In mass production, boring die is often used to improve boring efficiency.