1. Dimensional Accuracy of Shaft Parts
Juniors are the main surfaces of shaft parts, affecting the shaft's rotational accuracy and working condition. The diameter accuracy of journals is typically IT6-9, depending on usage requirements, with precision journals reaching IT5.
2. Geometric Accuracy of Parts
The geometric accuracy (roundness, cylindricity) of journals should generally be limited to the diameter tolerance range. For higher geometric accuracy requirements, allowable tolerances can be specified separately on the part drawing.
3. Machining Position Accuracy
This mainly refers to the coaxiality of the mating journal of the assembling transmission component relative to the supporting journal of the assembling bearing. It is usually expressed as the radial runout of the mating journal relative to the supporting journal. Depending on usage requirements, high-precision shafts are specified as 0.001-0.005 mm, while general-precision shafts are specified as 0.01-0.03 mm. Other requirements include the coaxiality of inner and outer cylindrical surfaces and the perpendicularity of the axial positioning end face to the axis.
4. Surface Roughness of Shaft Parts
Depending on the working part of the surface, different surface roughness values may exist. For example, the surface roughness of the spindle support journal of a common machine tool is Ra0.16～0.63um, and the surface roughness of the mating journal is Ra0.63～2.5um. As the machine operating speed increases and the precision improves, the surface roughness requirements for shaft parts will become smaller and smaller.
