
With the continuous improvement of the performance requirements of mechanical products, slender shaft parts are widely used. With the rapid development of aerospace, advanced equipment manufacturing, petrochemical and other industries, higher requirements are put forward for processing slender shaft parts. The elongated shaft parts are easy to bend and deform due to their own structures.
Based on the premise of optimizing product processing quality, controlling production cost and improving production efficiency, reasonable solutions of CNC turning machining are set up for possible problems.
This article will elaborate on the issues encountered during the turning process of slender shaft parts, and combine them with their characteristics to propose optimized methods for their turning.
Problems in the Turning Process

Slender shaft parts are spindly with poor rigidity. Due to the impact of cutting force, its own gravity action, cutting heat action and other factors, slender shaft parts may be bent and deformed during CNC turning machining.
Easy to Bend and Vibrate
The rigidity of slender shaft parts is poor due to the large diameter. Affected by cutting force, gravity and other external forces, it is easy to vibrate and deform during the processing. This in turn affects the parts’ positioning and causes inaccuracy, which is hard to achieve the required processing quality.
High Cutting Temperature Causes Deformation
The metal cutting process of shaft parts will generate cutting heat, which will increase the temperature of the cutting system. Slender shaft parts also face this problem during the cutting process. Due to the cutting heat, the workpiece is prone to deformation. The processing of some slender shaft parts will lead to local elongation, affecting the chuck rotation. But the distance between the chuck and the center won’t change, which causes the axial size change of the slender shaft parts when heated.
Tool Wear Affects Machining Quality
Because of its large axial size and small feed, the cutting processes take a long time when turning slender shaft parts. It causes wear to the tool, which is relatively serious. The tool wear directly leads to processing errors of slender shaft parts.
Optimization of Turning Slender Shaft Parts

Here are some optimization solutions for turning slender shaft parts.
Improve the Clamping of the Workpiece
When the slender shaft parts are turned, the clamping method is mainly divided into two forms: clamping while pushing and simultaneous pushing. Among them, clamping while pushing is used more extensively, because it is advantageous in convenient clamping, strong reliability, and withstanding the axial cutting force. In order to avoid the workpiece moving under the axial cutting force, the axial limit support device should be used to improve the clamping.
Apply the Reasonable Turning Method
Reasonable turning can optimize the processing process. For example, adopt reverse feed to complete the processing task of slender shaft parts, which can effectively avoid workpiece bending and deformation. The principle of reverse feed is mainly that the tool moves from the spindle box to the machine tail for cutting, and the normal direction of cutting movement is the opposite. The movement direction of the turning is consistent with the force acting on the workpiece of the tail seat of the machine tool and the direction of the axial cutting force. It will cause more serious bending problems of the elongated shaft parts.
Normally when the cutting movement is reversed, the direction of the feed force generated points to the lathe tail. It is consistent with the direction of the elongation deformation of the workpiece affected by the cutting heat, and points to the center direction of the lathe tail. There are also certain requirements for the cutting amount in processing, and the feed rate should be maximum to avoid obvious parts’ vibration.
Adjust Suitable Tool Geometric Parameters and Cutting Parameters
To improve the production quality and optimize production efficiency, reasonable tool geometry parameters can be adjusted from changing the cutting force, reducing the workpiece vibration and deformation as well as decreasing the cutting heat.
When turning spindly shaft parts, increase the cutting edge angle of the tool to reduce the radial cutting force and thus reduce its bending degree. From reducing the cutting force and cutting temperature, set a large front angle. The edge inclination can be set between 3° and 10°, ensuring reasonable control of the chip flow.
In the CNC turning machining of slender shaft parts, the cutting amount is the main parameter. And control cutting amounts within the appropriate range, which helps to fully stimulate and utilize the performance of machines and tools. It further improves the production efficiency and quality of slender shaft parts. During the reverse feed turning, set a larger feed when roughing, which can effectively improve the axial tensile stress of the workpiece and avoid vibration. In the process of roughing to finishing, the feed and back engagement gradually decrease, and the cutting speed gradually increases.
Full Use of Auxiliary Devices

For elongated shaft parts with large axial size, the rigidity of the parts’ middle position is poor, and auxiliary devices such as follow rest need to be applied to ensure stability. The follow rest is a unique auxiliary device for turning, which is fixed on the machine tool through the machine saddle, usually with two support pliers. In the processing, moving with the rest and cutters can effectively increase the parts’ stiffness during radial cutting, and further alleviate the deformation to enhance the shape accuracy and surface roughness.
The gravity of the slender shaft parts will also cause the bend and deformation of workpieces in actual production. Therefore, the workpiece is usually separated from the support clamp instantaneously under the centrifugal force, which then causes vibration.
If the structure of follow rest is improved, set the follow rest to the form of three supporting pliers. So that the workpieces’ X axis and the Z axis are limited, leading to stable turning and reduced vibration. In summary, when turning slender shaft parts, the follow rest with 3 supports can be auxiliary.
Conclusion
For the production of slender shaft parts, turning is more widely used at present. Because of its own parts limitations, parts bending is a serious problem in CNC turning machining, which can not meet the product’s processing requirements. Reasonable clamping is the application of the required tool geometric parameters and cutting parameters, auxiliary devices, etc. It guarantees the processing requirements of slender shaft parts, and then achieves high quality of the following assembly products.