Turning Processing Method

1. Rough turning is the most economical and effective method for rough machining of external cylindrical parts. Since the purpose of rough turning is mainly to quickly cut off excess metal from the blank, improving productivity is its main task.
Rough turning usually uses the largest possible back cutting amount and feed rate to improve productivity. In order to ensure the necessary tool life, the cutting speed is usually low. During rough turning, the turning tool should select a larger main deflection angle to reduce the back force and prevent the bending deformation and vibration of the workpiece; select a smaller rake angle, back angle and negative blade inclination angle to enhance the strength of the cutting part of the turning tool. The machining accuracy that can be achieved by rough turning is IT12~ITll, and the surface roughness Ra is 50~12.5μm.
2. Finish turning The main task of finishing turning is to ensure the machining accuracy and surface quality required by the parts. Finish turning of external cylindrical surfaces is generally processed with a smaller back cutting amount and feed rate and a higher cutting speed. When machining the outer circle of large shaft parts, wide-blade turning tools are often used for low-speed finishing. When finishing, the turning tool should use a larger rake angle, back angle and positive tool inclination angle to improve the surface quality. Finishing can be used as the final processing of high-precision external circles or as a pre-processing for fine processing. The processing accuracy of finishing can reach IT8~IT6 level, and the surface roughness Ra can reach 1.6~0.8μm.
3. Fine turning The characteristics of fine turning are: the back cutting amount and feed amount are extremely small, and the cutting speed is as high as 150~2000m/min. Fine turning generally uses superhard material tools such as cubic boron nitride (CBN) and diamond for processing. The machine tool used must also be a high-precision or precision machine tool with a high-speed spindle rotation and high rigidity. The processing accuracy and surface roughness of fine turning are roughly equivalent to those of ordinary external cylindrical grinding. The processing accuracy can reach above IT6, and the surface roughness Ra can reach 0.4~0.005μm. It is mostly used for precision machining of nonferrous metal workpieces with poor grinding performance. For workpieces such as aluminum and aluminum alloys that are easy to clog the pores of the grinding wheel, fine turning is more effective. When machining large precision outer cylindrical surfaces, fine turning can replace grinding.