Several commonly used trapezoidal thread metal parts turning methods
In order to ensure the machining accuracy and quality of thread surface roughness, we usually use high-speed steel lathe tool for low-speed turning. Commonly used low-speed turning methods include: straight-in method, left-right cutting method, straight groove method, and step groove method. Each of the four methods has its own advantages and disadvantages, but generally speaking, there are many disadvantages. In the process of processing, students are often prone to waste products due to improper handling of tool angles, improper operation methods, lathe clearance, and other reasons, thus discouraging student internships and enthusiasm.
(1) Straight forward method. The straight-in method is also referred to as slotting. In this method, in the actual machining process, only the infeed plate is used for lateral infeed for each turning, and the correct tooth shape and main cutting edge width are used to ensure the accuracy of the thread and the operation is relatively simple. However, when using this method, the three cutting edges of the turning tool are involved in cutting at the same time, and the turning tool is subject to greater force. If the tool material is not good and the angle is not properly handled, the cutting part of the turning tool may be broken or the knife may be easily broken.
(2) Left and right cutting methods. Each time the intermediate plate is moved into the blade, the small slide must be turned at the same time to make the longitudinal micro-displacement of the turning tool. This method can prevent the straight cutting method from causing the cutting part of the turning tool to break or tie the knife due to the simultaneous three-flute cutting. Since there are certain gaps in the small slides of the lathe, especially when the small stroke of the small slide is large, the longitudinal movement of the turning tool is not easy to control, and the machining is difficult, and it is difficult to ensure the accuracy of the thread. Therefore this method can only be used for threaded roughing.
(3) Straight groove method. Before machining, it is necessary to grind a rectangular thread turning tool. The width of the main cutting edge of the turning tool is equal to the width of the bottom of the tooth socket. Then the tool is used to process until the groove bottom diameter is equal to the trapezoidal thread path, and finally the correct trapezoidal shape is used. Thread fine turning tool fine thread on both sides. This method has high processing efficiency and precision, but due to the narrow width of the main cutting edge of the rectangular thread turning tool, the rigidity of the turning tool is poor during specific machining, and wear, breakage and the like are easily occurred.
(4) step groove method. During processing, use a pre-polished rectangular thread turning tool with a main cutting edge width less than P/2 to machine to the thread diameter in accordance with the principle of the straight groove method, and then use another width of the main cutting edge equal to the width of the bottom of the socket. The rectangular thread turning tool is turned close to the small thread, so there is a stepped thread groove. Finally, use the correct shape of the trapezoid thread threader to finish the threads on both sides. This method avoids the disadvantages of the straight groove method, and the cutting process is relatively smooth. However, three cutting tools are used successively. The tool change is troublesome, it is not easy to align the spiral straight groove, and the back teeth phenomenon is likely to occur.
The above are several commonly used metal parts turning methods. These methods have their own advantages and disadvantages, but they are generally not easy to grasp and the operation is cumbersome and needs to be further improved.