The main function of shaft parts is to support other rotating parts to rotate and transfer torque, and at the same time through the bearing and machine frame connection, is one of the important parts of the machine.

Shaft parts are rotating parts, its length is greater than the diameter, usually by the outer cylindrical surface, conical surface, inner hole, threads and the corresponding end of the composition. Shafts often also have splines, keyways, transverse holes, grooves and so on. According to the function and structural shape, there are various types of shafts, such as bare shafts, hollow shafts, half shafts, stepped shafts, spline shafts, crankshafts, camshafts, etc., which play the roles of support, guidance and isolation.

1. View expression

(1) shaft parts are mainly rotary body, generally in the lathe, grinder processing, commonly used in a basic view of the expression, the axis is placed horizontally, and will be placed on the right small head, easy to process when looking at the map.

(2) In the shaft of the single keyway is best towards the front to draw the full shape.

(3) For the structure of the shaft holes, keyways, etc., generally with a partial section view or sectional representation. In addition to clearly expressing the shape of the structure, it is also convenient to label the dimensional and form tolerances of the structure.

(4) retreat groove, rounded corners and other small structures with local enlargement of the expression.

2. Dimensional labeling

① The main datum in the length direction is the main end face (shoulder) of the mounting. The ends of the shaft are generally used as a measuring reference, and the axis is generally used as a radial reference.

② The main dimensions should be noted first, and the remaining multiple length dimensions are noted in the order of turning process. Most of the local structures on the shaft are located near the shoulder.

③ In order to make the labeled dimensions clear, easy to see, it is appropriate to separate the internal and external dimensions of the sectional view labeling, turning, milling, drilling and other different processes of the size of the separate labeling.

(4) For the chamfering, chamfering, backing groove, grinding wheel crossing groove, keyway, center hole and other structures on the shaft, the dimensions should be marked after consulting the relevant technical data.

3. Materials of shaft parts

① Shaft parts commonly used materials are 35, 45, 50 high-quality carbon structural steel, 45 steel is the most widely used, generally tempered, hardness of 230 ~ 260HBS.

② less important or less loaded shaft can be Q255, Q275 and other carbon structural steel.

③ large force, high strength requirements of the shaft, you can use 40Cr steel tempering treatment, hardness to 230 ~ 240HBS or hardened to 35 ~ 42HRC.

④ If it is a high-speed, heavy-duty conditions of the work of the shaft parts, the choice of 20Cr, 20CrMnTi, 20Mn2B and other alloy structural steel or 38CrMoAIA advanced high-quality alloy structural steel. These steels by carburizing quenching or nitriding treatment, not only the surface hardness, and its core strength is greatly improved, with better wear resistance, impact toughness and fatigue strength performance.

⑤ Ductile cast iron, high-strength cast iron due to the casting performance is good, but also has the vibration damping performance, commonly used in the manufacture of complex shape and structure of the shaft. In particular, China's rare earth magnesium ductile iron, good impact toughness, but also has a friction absorption, small sensitivity to stress concentration, etc., has been applied to automobiles, tractors, machine tools on the important shaft parts.

⑥ not after the final heat treatment to obtain high hardness of the screw, generally available tensile strength of not less than 600MPa 45 and 50 medium carbon steel. Precision machine tool screw can be used in carbon tool steel T10, T12 manufacturing. After the final heat treatment to obtain high hardness of the screw, with CrWMn or CrMn steel manufacturing, can ensure that the hardness of 50 ~ 56HRC.

4. Technical requirements of shaft parts

① Dimensional accuracy

The dimensional accuracy of the main journal diameter is generally IT6-IT9 level, and IT5 level for precision. For stepped shafts, the length of each step should be determined according to the requirements of the use of tolerance, or according to the requirements of the assembly dimensional chain to allocate the tolerance.

② Geometric Precision

Shafts are usually supported on bearings by two journals, which are the assembly reference of the shaft. The geometrical accuracy (roundness, cylindricity) of the supporting journals should generally be required. The general accuracy of the journal geometry and shape tolerance, should be limited to the diameter tolerance, that is, according to the inclusive requirements in the diameter tolerance labeled E, such as higher requirements, and then mark the allowable tolerance value (that is, after the size tolerance note E, and then add a box to mark the shape of the tolerance value).

③ Mutual positional accuracy

Shaft parts with the journal (assembly drive journal), relative to the support journal of the coaxiality of its mutual positional accuracy of the general requirements. For reasons of ease of measurement, radial runout is commonly used. The radial runout of the support journal is generally 0.01～0.03mm for ordinary precision shafts, and 0.001～0.005mm for high-precision shafts, in addition to the perpendicularity between the axial positioning end face and the centerline of the shaft.

④ Surface roughness

In general, the surface roughness of the support journal for Ra0.16 ~ 0.63um, with the surface roughness of the journal for Ra0.63 ~ 2.5um. For general-purpose parts, typical parts, the above items are generally available in the corresponding tables and information.