A Comprehensive Analysis of the Processing Technology of Ordinary Lathes

In the modern mechanical manufacturing system, the ordinary lathe is one of the most widely used basic processing equipment, accounting for approximately 65% of the total number of lathes. With its extremely strong versatility and flexibility, it has become an indispensable core equipment in various mechanical processing and maintenance scenarios. From simple shaft parts to complex thread and forming surface processing, ordinary lathes can stably complete production tasks with their mature technological systems.

Ⅰ. Core Structure and Process Foundation of Ordinary Lathes

The core components of a conventional lathe consist of the headstock, feed box, slide box, tool rest, tailstock, smooth screw, lead screw and bed. The precise fit of each component is the prerequisite for ensuring machining accuracy. As the core power unit, the spindle box provides different speeds for the spindle through an internal speed-changing mechanism, directly determining the smoothness of the workpiece's rotation and being a key link that affects the final processing quality. The slide box converts the rotational motion of the smooth screw and lead screw into the linear feed of the tool rest, respectively achieving the functions of ordinary tool feed and thread turning. Combined with the multi-layer movable tool rest, it can complete multi-dimensional cutting in the longitudinal, transverse and oblique directions. The tailstock can not only install the center support for long workpieces, but also carry drill bits, reamers and other hole processing tools, expanding the processing boundaries of the lathe.

From the perspective of process principles, the core logic of ordinary lathe processing is "the main rotational motion of the workpiece + the linear feed motion of the tool", and the cutting of various rotary body surfaces is completed through the cooperation of the two. This processing mode has three natural advantages: First, it is extremely easy to ensure the coaxiality of each processing surface of the workpiece. One clamping can complete the processing of multiple outer circles and inner holes, avoiding positional errors caused by multiple clamping. Second, the cutting process is continuous and stable. Apart from intermittent surface processing, there will be no impact of the cutting teeth repeatedly entering and exiting as in milling, allowing for the use of larger cutting parameters to enhance efficiency. Thirdly, the structure of the turning tool is simple, with low difficulty in manufacturing, grinding and installation. The tool Angle can be flexibly adjusted according to different materials, and it has extremely strong adaptability.

Ⅱ. Mainstream Processing Techniques and Applicable Scenarios

The processing coverage of ordinary lathes is extremely wide. Almost all rotary parts can complete the full-process processing on the equipment. The core processes can be divided into several major categories:

1. Basic rotary surface processing: It includes basic procedures such as turning outer circles, end faces, inner holes, and conical surfaces. It is the most commonly used processing method for shaft and disc sleeve parts. From rough turning to quickly remove the allowance, to semi-finishing turning to correct the contour, and then to finishing turning to ensure accuracy, the dimensional accuracy can be stably controlled within the IT7-IT8 range, and the surface roughness can reach Ra1.6-3.2μm. For non-ferrous metal parts, even higher processing quality can be achieved through fine turning, avoiding the surface adhesion problem that is easily caused by grinding processing.

2. Thread and special surface processing: Relying on the strict transmission ratio fit between the lead screw and the spindle, ordinary lathes can process various metric and imperial threads. Whether it is external threads, internal threads or special threads with large leads, they can all be completed by adjusting the parameters of the feed box. In addition, it can also complete processes such as knurling and turning the rotary forming surface, meeting the anti-slip and special shape requirements of the parts.

3. Special Extended process: Traditionally, lathes were only capable of processing circular contours. However, the polygonal turning process has broken this limitation. By precisely controlling the rotational speed ratio of the workpiece to the tool, the tool can repeatedly cut at a specific position without multiple clamping operations, enabling the processing of non-circular contours such as hexagons and squares. This significantly enhances the batch production efficiency of hexagonal bolts and special-shaped drive shafts. In combination with drilling, reaming and boring tools, ordinary lathes can also complete the center hole processing of shaft parts and the fine processing of inner holes of disc and sleeve parts, achieving the processing effect of "one machine with multiple uses".

Ⅲ. Key Points for Process Optimization and Safe Operation

To consistently achieve high-quality processing results, the control of process details is of vital importance. During the rough turning stage, a large feed rate should be given priority to quickly remove the allowance. The tool Angle selection should focus on impact resistance to avoid chipping during cutting. During the fine turning stage, the spindle speed should be appropriately increased, the feed rate reduced, and a reasonable tool polishing edge should be used to ensure the final surface quality. For slender shaft parts, when the overhang length of the workpiece exceeds four times the diameter, a center rest or tool rest must be used for support to prevent the workpiece from vibrating and deforming during the cutting process and to ensure the straightness accuracy.

Operation norms are the core guarantee for the implementation of processes: When aligning workpieces, it is only allowed to manually operate the chuck or set the lowest speed. High-speed alignment is strictly prohibited to prevent safety accidents. Before changing the rotation direction of the main shaft, the main shaft must be stopped first. It is strictly prohibited to directly switch the handle to impact the transmission structure. When loading and unloading large-sized chucks, wooden boards should be placed on the bed surface to prevent the chucks from falling and damaging the guide rail surface. When installing the cutting tool, the overhang length should not be too long. The tool pads should be flat and aligned to prevent vibration during the cutting process. When processing brittle metals or operations where chips are prone to splashing, protective baffles must be installed and operators must wear goggles to avoid the risk of being scalded or scratched by chips.

From single-piece and small-batch maintenance scenarios to assembly line-style mass production, ordinary lathes, with their mature technological systems, extremely low usage costs and strong adaptability, remain the "cornerstone equipment" in the field of mechanical manufacturing to this day. With the upgrading of tool materials and the continuous optimization of operation techniques, this classic equipment is still constantly releasing new productivity, providing stable and reliable solutions for the processing of various parts.