The journals are the assembly reference of the shaft, and their accuracy and surface quality are generally required to be high. The technical requirements are generally formulated according to the main functions and working conditions of the shaft, and usually have the following items:
1. Dimensional accuracy: The journals that play a supporting role usually require high dimensional accuracy (IT5~IT7) in order to determine the position of the shaft. The dimensional accuracy of journals for assembled transmission parts is generally required to be lower (IT6~IT9).
2. Geometric shape accuracy: the geometric shape accuracy of shaft parts mainly refers to the roundness, cylindricity, etc. of the journal, external taper surface, Morse taper hole, etc., which should generally be limited to the tolerance within the dimensional tolerance. For high accuracy requirements of the internal and external circular surfaces, should be marked on the drawing its allowable deviation.
3. Mutual position accuracy: the position accuracy requirements of shaft parts are mainly determined by the position and function of the shaft in the machinery. Usually should ensure that the assembly transmission parts of the journal support journal coaxial requirements, otherwise it will affect the transmission accuracy of the transmission parts (gears, etc.), and generate noise. The radial runout of the supporting journals of the mating shaft section is generally 0.01~0.03mm for ordinary precision shafts, and 0.001~0.005mm for high precision shafts (such as spindles).
The heat treatment process of precision parts:
1. by heat treatment, HRC50 ~ 55.
2. low carbon steel: 45 or 40Cr parts carry out induction quenching, 350 ~ 370 ℃ quenching, HRC40 ~ 45.
3. Nitriding deep layer 0.3mm.
4. Carry out continuous high-temperature tempering treatment.
