Processing Accuracy 1) Dimensional Accuracy The dimensional accuracy of shaft parts mainly refers to the shaft diameter dimension accuracy and shaft length dimension accuracy. According to the requirements of use, the accuracy of the main journal diameter dimension is usually IT6-IT9, and the precision journal can also reach IT5 level. The length of the shaft is usually specified as a nominal dimension, and the length of each step of the stepped shaft can be given a tolerance according to the requirements of use. 2) Geometric Accuracy Shaft parts are generally supported on bearings by two journals. These two journals are called support journals and are also the assembly standards for the shaft. In addition to the dimensional accuracy, the geometrical accuracy (circularity, cylindricity) of the support journal is generally required. For general-precision journals, geometrical errors should be limited to diameter tolerances. When requirements are high, allowable tolerance values should be specified on the part drawing. 3) Mutual Positional Accuracy The coaxiality of the fitting journals (shafts of the assembly transmission components) in the shaft-like components relative to the support journals is a common requirement for their mutual positional accuracy. Normally, the accuracy of an axis is generally 0.01-0.03 mm for the radial runout of the support journal and 0.001-0.005 mm for the high-precision axis. In addition, the mutual position accuracy also includes the coaxiality of the inner and outer cylindrical surfaces, the perpendicularity of the axial positioning end surface and the axis of the shaft, and the like.
the surface roughness According to the degree of mechanical precision, the level of speed, shaft parts surface roughness requirements are not the same. Under normal circumstances, the surface roughness Ra of the supporting journal is 0.63-0.16 μm; the surface roughness Ra of the fitting journal is 2.5-0.63 μ.