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Lathe Turning Training Log
The several-day turning training has come to a successful conclusion. During this practice, I systematically learned about the structural principles, model parameters, basic operations of ordinary lathes, as well as core knowledge of metal cutting processing. Starting from getting familiar with lathe equipment and memorizing the coding rules of lathe models, to mastering the three cutting parameters and various processing technologies, and further independently completing basic practical procedures including drilling, external turning, thread cutting and knurling, I have not only consolidated the professional theoretical foundation of mechanical processing, but also improved my practical operation capabilities. I have deeply realized the rigorous, precise and standardized core requirements of the mechanical processing industry. I hereby record the studies, practical operations and insights of this turning training in detail as follows.
In the initial stage of the training, the teacher first led us to conduct theoretical cognition of lathe equipment, focusing on explaining the model compilation rules of ordinary horizontal lathes. This is the fundamental core knowledge for beginners in turning, and also a key content I strived to master throughout the training. Previously, I had no understanding of lathe model codes. Through systematic learning, I fully grasped the coding meanings of two classic horizontal lathes, the C620-1 and CA6140, and clarified the differences between old and new models as well as their disparities in equipment performance.
The C620-1 is a traditional old-fashioned horizontal lathe and a classic processing equipment widely used in factories in the past. In its model code, the initial letter "C" is the general code for lathes, representing that the machine tool category is lathe; the digit "6" stands for the equipment structural form, i.e., horizontal lathe, which distinguishes horizontal lathes from vertical ones; the number "20" refers to the core parameter of the lathe, namely the maximum machining radius from the lathe bed surface to the spindle, which determines the maximum machining size range of the equipment. The horizontal line in the model indicates that this machine is an original basic model, and the trailing digit "1" means the equipment has undergone one structural improvement. Compared with new-style lathes, the old C620-1 features a simple structure and basic functions. Restricted by its mechanical layout, it supports a narrow range of processing materials and limited machining diameters. Besides, it is equipped with few spindle speed gears with low speed adjustment precision, resulting in poor machining accuracy and low working efficiency. At present, it is mostly applied to simple rough machining training and basic operations in outdated workshops.
In contrast, the CA6140 is the mainstream new horizontal lathe for training and industrial production at present, with far superior performance to the outdated C620-1. In its model, "C" still serves as the lathe code, while the letter "A" represents a major structural upgrade — an optimized and redeveloped version based on the basic model, which greatly improves the mechanical layout, transmission system and precision performance of the equipment. The digit combination "61" is the type code of the lathe, differentiating its structural layout from old lathes. The final number "40" is the core processing parameter, indicating the maximum machining diameter of this lathe reaches 400 millimeters, granting it a wider machining size range and stronger compatibility. Meanwhile, the CA6140 supports left-hand thread machining, making up for the functional deficiency of old lathes. It can process a variety of metal materials, and users can flexibly adjust spindle speed and feed rate according to workpieces of different materials and diameters. With remarkable improvements in machining accuracy, operational stability and versatility, it acts as the primary processing equipment in mechanical workshops.
After mastering lathe models and equipment characteristics, we moved on to study the core theory of turning processing: the three cutting parameters. These parameters form the theoretical basis for all turning operations, directly determining workpiece processing quality, tool wear and machining efficiency, and are critical indicators that lathe operators must strictly control in practice. The three cutting parameters consist of cutting speed, cutting depth and feed rate, which interact and restrict one another, all being indispensable.
Cutting speed refers to the relative moving speed between the cutting edge of the tool and the workpiece surface. Its adjustment mainly depends on workpiece material, tool material and machining precision requirements. For high-hardness steel workpieces, the cutting speed should be reduced to avoid tool edge chipping and surface burning of workpieces; for soft materials such as aluminum and copper, the spindle speed and cutting speed can be appropriately increased to raise processing efficiency. The old C620-1 lathe is fitted with limited fixed speed gears, failing to accurately match the cutting speed requirements of various materials, whereas the CA6140 provides a wide speed adjustment range with refined gears to accommodate the cutting demands of diverse materials.
Cutting depth means the depth the tool cuts into the workpiece in a single turning pass, mainly affecting machining allowance and dimensional accuracy of workpieces. In rough machining, the cutting depth can be properly increased to quickly remove excess material and boost efficiency; in finish machining, the cutting depth must be reduced to trim dimensions layer by layer, ensuring flat workpiece surfaces and precise measurements, and preventing dimensional deviations, surface scratches and other defects.
Feed rate represents the axial distance the tool travels for every full rotation of the workpiece. An excessively large feed rate will cause rough workpiece surfaces with obvious tool marks, and may even lead to tool breakage and workpiece deformation. An overly small feed rate drastically lowers processing efficiency, and may result in prolonged friction between the tool and workpiece, causing thermal deformation, annealing and blackened surfaces of workpieces. In practical operations, operators need to reasonably match the three cutting parameters according to rough and finish machining demands to balance efficiency and product quality.
Upon finishing theoretical studies, we entered the practical skill training phase, systematically practicing the use of core lathe tooling fixtures and various turning technologies. The first fixture we learned was the three-jaw chuck, the core component for clamping workpieces. Operators must master clamping techniques before conducting any processing. When fixing workpieces, it is essential to ensure tight clamping and coaxial alignment of the workpiece axis, so as to prevent workpiece loosening and eccentricity during processing, which would otherwise trigger dimensional errors or even safety accidents. In addition, clamping force should be moderate: insufficient force leads to workpiece shaking, while excessive force may squeeze thin-walled workpieces and cause deformation. This is the most fundamental yet critical operational detail in turning practice.
In the training of basic processing procedures, I practiced conventional lathe processing projects one by one, covering forming machining, hole machining and texture machining technologies. Basic forming processes include external turning, facing, internal boring, taper turning and thread cutting, which constitute the core fundamental procedures for lathe operators. Facing trims the flatness of workpiece end faces to guarantee the end face is perpendicular to the spindle axis; external turning is the most widely used process for machining cylindrical outer contours of workpieces; internal boring is applied to process inner dimensions of sleeve and ring workpieces; taper turning requires fine-tuning the angle of the lathe compound rest to accurately control taper and ensure perfect fitting of tapered surfaces; thread cutting covers standard right-hand threads and the exclusive left-hand threads supported by new lathes. During thread machining, operators must match corresponding spindle speeds and feed ratios to obtain regular thread profiles and accurate pitches.
Apart from conventional forming processing, I also learned forming surface machining, straight knurling and diamond knurling technologies. Knurling is mostly used on anti-slip workpieces such as handles and knobs. Straight knurling produces neat vertical textures, while diamond knurling forms crisscross patterns. In practice, special knurling tools need to be installed, and appropriate spindle speed and feed rate must be adjusted to achieve uniform textures with consistent depth, avoiding skewed or uneven patterns.
In hole machining training, I became proficient in using center drills, twist drills and reamers, following standardized process flows. When manufacturing deep holes or high-precision holes, the first step is to drill a center hole with a center drill to precisely locate the hole center and prevent drill bit deflection and eccentric holes. After positioning, twist drills are adopted for rough drilling to remove most machining allowance. Finally, reamers are used for finish reaming to calibrate hole diameters and improve the smoothness of hole walls, meeting the assembly requirements of high-precision components. Meanwhile, I learned the application scenarios of spring auxiliary supports matched with lathes in the training. When processing slender shafts, spring supports can reduce workpiece vibration and deformation to improve machining precision.
I encountered numerous problems during practical operations, and corrected them one by o
