Lathe shaft parts are the main parts in mechanical equipment, which usually play the role of supporting transmission and transmitting torque.
1. Structural forms of shaft parts The structural forms of shaft parts can be divided into optical shafts, stepped shafts and spline shafts, etc. They are generally composed of cylindrical surfaces, steps, end faces, chamfers, arcs and grooves. What they do is:
1) Cylindrical surfaces are generally used to support transmission parts (such as gears, sheaves, etc.) and transmit torque, etc.
2) Steps and end faces are generally used to determine the axial position of the parts installed on the shaft.
3) The function of chamfering is to facilitate the assembly of other parts on the one hand, and to remove the sharp corner burrs of the parts to prevent hand injury. Therefore, except for special requirements, the sharp corners of the parts should generally be chamfered.
4) The arc can eliminate stress concentration, improve the strength of the shaft, and avoid defects such as cracks in the heat treatment process of the shaft.
2. The technical requirements of shaft parts are the technical requirements of shaft parts, and the lathe mainly includes machining accuracy, surface quality and heat treatment requirements.
(1) Dimensional accuracy mainly includes the dimensional accuracy of diameter and length, especially the dimensional accuracy of diameter.
The diameter of the shaft is an important datum plane for parts assembly. Only when a considerable dimensional accuracy is achieved can the installation accuracy of the mechanical assembly be guaranteed.
(2) Shape accuracy includes roundness, straightness, flatness and cylindricity.
(3) Position accuracy includes coaxiality, circular runout, perpendicularity and parallelism.
(4) Surface roughness In order to ensure the technical requirements of machining accuracy, the surface quality of the machined surface must be improved. When turning medium carbon steel materials on an ordinary lathe, the surface roughness value is R. The lathe generally can reach 1_ 6run. Under special conditions, when turning precision threads, thread plug gauges, and thread ring gauges, the surface roughness value ruler. Up to 0.4pm or more.
(5) Shafts with important heat treatment requirements should generally be heat treated.
1) Normalize or deal with fire. Lathe normalizing or annealing treatment can refine the grains inside the steel, eliminate the internal stress caused by the original or after forging and casting, reduce the hardness of the material, and improve the cutting performance. Lathe normalizing or annealing is usually carried out before cutting or after rough turning.
2) Quenching and tempering treatment. Lathe quenching and tempering can not only obtain good comprehensive mechanical properties, reduce the deformation of subsequent processing, but also improve the cutting performance and improve the smoothness of the machined surface. It is a commonly used heat treatment process for shaft parts. Quenching and tempering treatment is generally arranged after roughing and before semi-finishing.
3) Surface quenching treatment. The surface quenching treatment of the lathe is to improve the hardness, wear resistance and fatigue strength of the steel working surface, and the core still maintains good toughness, that is, the performance state of external hard and internal toughness. There are two commonly used methods: one is to harden the carburized layer with a depth of 0.5 and 2.5 mm on the surface of the parts of low carbon steel or low alloy steel; the other is to harden the medium carbon steel or medium carbon alloy structural steel. The surface of the parts is hardened by induction heating. Surface hardening is generally arranged after semi-finishing and before finishing.