The technical requirements of metal machining are generally formulated according to the main function and working conditions of the shaft, usually the following:

(a) Surface roughness of precision parts

Generally, the surface roughness of the shaft diameter matched with the transmission is Ra2.5~0.63μm, and the surface roughness of the supporting shaft diameter matched with the bearing is Ra0.63~0.16μm.

(b) Precision of mutual position of precision parts

The position accuracy requirements of metal machining are mainly determined by the position and function of the shaft in the machine. It is usually necessary to ensure the coaxiality requirements of the shaft journal of the assembly transmission parts to the supporting shaft journal, otherwise it will affect the transmission accuracy of the transmission parts (gears, etc.) and produce noise. For ordinary precision shafts, the radial runout of the supporting journal with the shaft segment is generally 0.01~0.03mm, and high-precision shafts (such as the main shaft) are usually 0.001~0.005mm.

(c) Precision parts geometry accuracy

The geometric accuracy of shaft metal machining mainly refers to the roundness and cylindricity of shaft journal, outer cone, Morse cone hole, etc., and its tolerance should generally be limited within the range of dimensional tolerance. For the inner and outer circular surfaces with higher accuracy requirements, the allowable deviation should be marked on the drawing.

(d) Dimensional accuracy of non-standard parts processing

In order to determine the position of the shaft, the bearing journal usually requires higher dimensional accuracy (IT5~IT7). The size accuracy of the journal of the assembly transmission is generally low (IT6~IT9).

Precision parts centering CNC lathe (centring lathe/slitting lathe) is a kind of CNC machine tool mainly used in shaft and non-standard shaft precision machining, it has a qualitative leap in processing efficiency and processing accuracy than CNC lathe, due to the use of dual-axis arrangement tools, greatly reduce the processing cycle time, by shortening the tool exchange time between the row tool and the opposite tool table, Multiple tool table overlapping function, thread chip effective shaft moving overlapping function, direct spindle indexing function during secondary machining, to achieve the reduction of empty travel time. The chip cutter is always processed at the clamping part of the spindle and the workpiece, ensuring that the accuracy of the processing remains unchanged. At present, the machining diameter of the machine on the market is 42mm, which has great advantages in the precision shaft processing market. This series of machine tools can be equipped with automatic feeding device to achieve fully automated production of a single machine tool, reducing labor costs and product defect rate. Metal machining is suitable for mass production of precision shaft parts.