Turning is a machining process in which a cutting tool, usually a non-rotational tool bit, describes the path of the helix tool, moving more or less linearly when rotating the workpiece.
Typically, the term "turning" is reserved for generating external surfaces by this cutting action, while the same basic cutting action when applied to internal surfaces (holes, other types) is called "boring". So the phrase "turning and boring" divides a larger family of processes known as turning. Cutting a surface on a workpiece, whether with a turning or boring tool, is called "facing" and can be compacted in one or the other category as a subset.
Turning can be done manually, in a traditional lathe, which often requires constant operator supervision, or with an automatic lathe that does not. Currently, the most popular type of such automation is computer numerical control, better known as CNC. (CNC is also widely used in many other types of machining besides turning).
When turning, the workpiece (piece of relatively rigid material such as wood, metal, plastic or stone) is rotated and the cutting tool is moved along the 1st, 2nd or 3rd axis of movement to obtain precise diameters and depths. Turning can take place outside the cylinder or inside (also known as boring) to produce tubular elements with different geometries. Although quite rare now, early lathes can even be used to create complex geometric figures, even Platonic solids; although, since the appearance of CNC, it has become remarkable to use non-computerized tool path control for this purpose.
Turning processes are usually performed on a lathe, considered the oldest of machine tools, and can be of various types, such as straight turning, conical turning, profiling or external grooving. These types of turning processes can produce different shapes of materials, such as straight, tapered, curved or grooved workpieces. Basically, simple one-point cutting tools are used for turning. Each group of workpieces has an optimal set of tool angles developed over the years.
Pieces of metal waste from turning operations are known as chips (North America) or swarf (United Kingdom). In some areas they may be known as chips.
The axes of movement of the tool can be literally a straight line or can run along a certain set of curves or angles, but they are essentially linear (in a non-mathematical sense).
The part subject to turning operations can be called "turned part" or "machined part". Turning takes place on a lathe, which can be operated manually or CNC.
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Enabling specific operations includes:
The general turning process is turning the parts, while the single point cutting tool is moved parallel to the axis of rotation. Turning can be performed on both the outer surface of the part and the inner surface (a process known as boring). The starting material is essentially a workpiece generated by other processes such as casting, forging, extrusion or drawing.
- Conical Turning
Conical turning gives a cylindrical shape that gradually reduces the diameter from one end to the other. This can be achieved a) with a compound slide b) with a cone turning tool c) with a hydraulic copying tool d) with C.N.C. lathe e) using a forming tool f) by moving the tailstock - this method is more suitable for shallow constrictions.
- Spherical Generation
The spherical generation produces a spherically finished surface by rotating the mold around a fixed axis of rotation. The methods include: a) the use of a hydraulic copying device b) C.N.C. (computer numerically controlled) lathe c) using a molding tool (rough and ready method) d) using a bed positioning tool (please explain the drawing).
- Difficult Turning
Hard turning is a type of turning performed on materials with a Rockwell C hardness greater than 45. Usually it is performed after the heat treatment of the workpiece.
This process is intended to replace or reduce traditional milling operations. Hard turning, when used exclusively to remove material, preferably competes with rough grinding. However, when used for finishing, where form and dimensions are critical, sanding is better.
Grinding provides greater dimensional accuracy of roundness and cylindricality. In addition, polished surface finishes Rz = 0.3-0.8z cannot be achieved with hard turning alone. Hard turning is suitable for parts requiring a roundness accuracy of 0.5-12 microns and / or a surface roughness of 0.8-7.0 microns. It is used, among others, for gears, injection pump components and hydraulic components.
Facing in the context of turning consists in moving the cutting tool at a right angle to the axis of rotation of the rotating workpiece. This can be done by means of a cross slide, if fitted, as opposed to longitudinal travel (turning). Often this is the first operation performed in the production of the object, and often the last - hence the phrase "ending".
This process, also known as parting or cutting off, is used to create deep grooves that remove the finished or partially complete component from the parent stock.
- External Grooving/Face Grooving
Grooving is like cutting, except that the grooves are cut to a specific depth instead of cutting the finished / partial element out of stock. Grooving can be done on internal and external surfaces, as well as on the surface of parts (surface grooving or trepanning).
Non-specific operations include:
Enlarging or smoothing the existing hole created by drilling, forming, etc. machining of internal cylindrical forms (generating) a) by clamping the workpiece to the spindle using a chuck or face plate b) by mounting the workpiece on a cross slide and placing the cutting tool in the chuck. This work is suitable for castings that are too uncomfortable to mount them in the front plate. On long bed-type lathes, a large workpiece can be screwed to the chuck on the bed, and the shaft can pass between the two projections of the workpiece, and these lugs can be cut to size. Limited use, but one that is available to a qualified turner / mechanic.
This is used to remove material from inside the workpiece. In this process, standard drills are used that are held still in the tailstock of lathe tool head. This process can be done using separately available drills.
Cutting out a serrated pattern on the surface of the part for use as a hand grip or as a visual improvement with a special knurling tool.
A resizing operation that removes a small amount of metal from an already drilled hole. This is used to make internal holes with very accurate diameters. For example, a 6 mm diameter hole is made by drilling with a 5.98 mm drill and then reaming to exact dimensions.
:: Read more : Turning Center and Machining Center: A Comparison
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