Working Principle Of Turning Lathe

Workpiece rotation is a cutting process in which the turning tool moves in a straight or curved line within a plane. Turning is generally carried out on a lathe to process the inner and outer cylindrical surfaces, end faces, conical surfaces, forming surfaces, and threads of workpieces.
When turning inner and outer cylindrical surfaces, the turning tool moves in the direction parallel to the axis of rotation of the workpiece. When turning the end face or cutting the workpiece, the turning tool moves horizontally along the direction perpendicular to the rotation axis of the workpiece. If the motion trajectory of the turning tool is at an angle to the axis of rotation of the workpiece, a conical surface can be machined. The surface of the rotating body formed by turning can be formed using either the forming tool method or the tool tip trajectory method. During turning, the workpiece is driven by the spindle of the machine tool to rotate as the main motion; The turning tool clamped on the tool holder performs a feed motion. The cutting speed v is the linear velocity (in meters/minute) at the contact point between the machining surface of the rotating workpiece and the turning tool; The cutting depth is the vertical distance (in millimeters) between the surface to be machined and the already machined surface of the workpiece during each cutting stroke, but in cutting and forming turning, it is the contact length (in millimeters) between the turning tool perpendicular to the feed direction and the workpiece. The feed rate represents the displacement of the turning tool along the feed direction for each revolution of the workpiece (in millimeters per revolution), which can also be expressed as the feed rate of the turning tool per minute (in millimeters per minute). When turning ordinary steel with high-speed steel turning tools, the cutting speed is generally 25-60 meters per minute, and the hard alloy turning tool can reach 80-200 meters per minute; When using coated hard alloy turning tools, the maximum cutting speed can reach over 300 meters per minute.
Turning is generally divided into two categories: rough turning and precision turning (including semi precision turning). Rough turning aims to improve turning efficiency by using large cutting depths and large feed rates without reducing cutting speed, but the machining accuracy can only reach IT11 and the surface roughness is R α 20-10 microns; Semi precision and precision turning should use high-speed and smaller feed rates and cutting depths as much as possible, with machining accuracy of IT10-7 and surface roughness of R α 10-0.16 microns. Using finely polished diamond turning tools on high-precision lathes for high-speed precision turning of non-ferrous metal parts can achieve machining accuracy of IT7-5 and surface roughness of R α 0.04-0.01 micrometers. This type of turning is called "mirror turning". If a concave or convex shape of 0.1-0.2 microns is cut on the cutting edge of a diamond turning tool, the surface of the turning will produce extremely small and neatly arranged stripes, which will present a satin like luster under the diffraction of light. It can be used as a decorative surface, and this type of turning is called "rainbow turning".
When turning, if the turning tool rotates in the same direction as the workpiece at the corresponding speed ratio (the tool speed is usually several times the workpiece speed), the relative motion trajectory between the turning tool and the workpiece can be changed, and the workpiece with a cross-section of polygons (triangles, squares, prisms, and hexagons, etc.) can be processed. If a periodic radial reciprocating motion is added to the tool holder relative to each rotation of the workpiece while the turning tool is longitudinally fed, the surface of the cam or other non circular cross-section can be machined. On a tooth relief lathe, according to a similar working principle, the back face of the teeth of certain multi tooth cutting tools (such as forming milling cutters and gear hobbing cutters) can be machined, which is called the "back relief".