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Turning Operations and Machines
Published in Zainul Huda, Machining Processes and Machines, 2020
In straight turning, the cutting tool moves longitudinally to produce straight cuts in the work; a rake angle of around 5° is recommended for the best cutting action in straight turning. In taper turning, there is a gradual reduction in diameter from one end of the cylindrical workpiece to the other end; this gradual reduction in diameter is accomplished by offsetting the tailstock of the lathe. In facing (or face turning), the tool is fed radially inward toward the center at the end of the work. In boring, a boring cutting tool is used to enlarge a hole usually made by a previous process. In contour turning, the tool follows a contour on the work thereby generating a contoured shape. In form turning, a form tool is fed perpendicular to the axis of rotation of the work to form the shape. In cut-off turning, the tool is fed perpendicular to the axis of rotation of the work at a location to cut-off end of the work. In grooving, the cutting tool moves longitudinally to produce a groove in the work. In thread turning, a pointed form tool is fed linearly across surface of work at a larger feed rate thus producing threads. In knurling, a pattern of straight, angled, or crossed lines is machined into the workpiece. Engineering analyses of some commonly practiced turning and related operations are presented in Section 5.5.
General-Purpose Metal-Cutting Machine Tools
Published in Helmi Youssef, Hassan El-Hofy, Traditional Machining Technology, 2020
Boring is the machining process in which internal diameters are generated in true relation to the centerline of the spindle by means of single-point tools. It is the most commonly used process for enlarging and finishing holes or other circular contours. Although most boring operations are performed on simple straight-through holes, the process may be also applied to a variety of other configurations. Tooling can be designed for boring blind holes, holes with bottle configurations, circular-contoured cavities, and bores with numerous steps, undercuts, and counterbores. The process is not limited by the length-to-diameter ratio of holes. Boring is sometimes used after drilling to provide drilled holes with greater dimensional accuracy and improved surface finish. It is used for finishing large holes in castings and forgings that are too large to be produced by drilling.
Machining of Metals
Published in Sherif D. El Wakil, Processes and Design for Manufacturing, 2019
Boring involves enlarging a hole that has already been drilled. It is similar to internal turning and can, therefore, be performed on a lathe, as previously mentioned. There are also some specialized machine tools for carrying out boring operations. These include the vertical boring mill, the jig-boring machine, and the horizontal boring machine.
Lathe boring operation on ASTM A304 steel parameter optimization using response surface methodology
Published in Australian Journal of Mechanical Engineering, 2021
Christopher Okechukwu Izelu, Emmanson Itoro Essien, Modestus Okechukwu Okwu, Danladi King Garba, Christopher Nonye Agunobi-Ozoekwe
Machining constitutes a major operation performed in manufacturing of machine parts. During most machining processes, heat and vibration have always been major problems. These affect tool life as well as the surface quality of the finished products. As reported in Kalpakjian and Schmid Steven 2000), machining operations are numerous. However, of interest is boring operation, which is often regarded as the process of enlarging a straight hole that has already been cast, formed and/or drilled by means of a cutting tool with some degree of accuracy. It can also be used to create a tapered hole, and in the manufacture of gun barrel, car engine cylinders, bearing sittings and numerous others. Boring process, amongst others, is often executed on lathe machines, and in special situations, on boring mills of any chosen configuration depending on the task performed. The process can be performed effectively by skilled labour using manual, semi-automatic, automatic machines. However, the need for optimum results required to achieve high-quality products cannot be over stressed. This paper therefore reports an investigation undertaken to reveal the effect the machining conditions, such as feed rate (FR), cutting speed (CS), and depth of cut (DOC), have on the process performance parameters, such as tool wear (TW), cutting temperature (CT) and material removal rate (MRR) during the lathe machining process involving boring operation on ASTM A304 low alloy steel using tungsten carbide inserts. The response surface methodology (RSM), based on 3-level factorial design of experiment (DOE) is therefore used to model, predict and optimise some selected lathe boring performance parameters against the basic machining conditions, all other parameters being kept constant. Data analysis was undertaken with the aid of the Design Expert software, version 9.0.6.2.
Experimental investigation on boring of HSLA ASTM A36 steel under dry, wet, and cryogenic environments
Published in Materials and Manufacturing Processes, 2019
C. Chandrasekhara Sastry, P. Hariharan, M. Pradeep Kumar, M. A. Muthu Manickam
Pipes play a major role in transporting liquids and gases in our day-to-day lives. In order to achieve this, drilling operation is carried out to produce holes of required dimensions. Drilling being an intricate process, the hole quality produced is contrived by different conditions such as workpiece material, attribute of the operation, tool material, cutting zone temperature, and cutting force.[1] Secondary operations, viz., reaming, broaching, boring, etc., are carried out to overcome the defects caused in drilling and to obtain close geometric tolerance values of the hole produced. In the reaming process, a reamer is used, which is a multi-tooth cutter which rotates and moves linearly into a drilled hole or an existing hole. Reaming operation provides close tolerances compared to other secondary operations. The main drawback of the reaming process is that it follows the already existing hole produced during the drilling cycle. Thus, reaming will not provide any significant changes if hole misalignments are present. Additionally, any misalignment which is preexisting due to the drilling process will damage the reamer if mounted on a conventional spindle for machining operation due to the high flexibility of the tool.[2] Furthermore, in secondary hole-making operations, the major constraint and limitation are when the hole machined is to be enlarged to a non-standard dimension. This is where boring finds its footing and is applicable in hole making of standard and nonstandard dimensions by choosing an appropriate tool. Ihsan Korkut et al.[3] after repeated experimental analysis in studying the deviation of circularity of bored holes by using Taguchi method determined that in boring operation, the length/diameter value of tool should be less than 3 for optimum results. Sudhanshu Kumar et al.[4] performed a nonconventional boring operation, and it was observed that the radial strategy of electrical discharge machining (EDM) is better suited for a boring operation compared to helical boring operation as the wear ratio is minimum. Operations that are also hole making include counterboring, spot facing, and countersinking. For all these operations, boring is the primary operation to accommodate different types of tools required for further enlarging the hole or for improving its surface characteristics.
Experimental investigation of dry, wet and cryogenic boring of AA 7075 alloy
Published in Materials and Manufacturing Processes, 2019
C. Chandrasekhara Sastry, P. Hariharan, M. Pradeep Kumar
Pipeline transport plays a significant role in transportation of liquids and gases. With a view to obtain pipes of different dimensions, the hole-making process plays a momentous role in which a drilling operation is carried out followed by a boring process. Boring is considered to be an internal turning operation to enlarge a drilled or cast hole. Boring is carried out on circular contours for producing close tolerance holes. It is also done to produce holes of standard and non-standard dimension based on the geometric necessity.[1] For every machining operation, the most important entity is the cutting fluid or coolants introduced during the machining cycle. The functions of a cutting fluid or a coolant are to curtail the temperature, mitigate friction in the area under machining, shield the workpiece against corrosion, removal of chips during machining which when not removed leads to change in surface characteristics by producing wear tracks along the path of the machining operation, ameliorate the surface of the machined component and preclude the generation of a built-up edge.[2] Studies carried out indicated that the cutting fluid application can be done in three types of method, viz., back of the chip, along the rake crevice within the chip and the tool and over the course of clearance face of the tool.[2–6] In each of these methods, the type of flow can be in the form of flooding, jet spray and mist based on the type of material being machined and application. In flood cooling application, a large volume of flow of cutting fluid is experienced on the back of the chip at the cutting zone. As the name suggests, flooding ensures minimum heat generation due to vast amount of cutting fluid presence during the machining cycle. However, a major constraint of the same due to excessive presence of cutting fluid leads to slip stick phenomenon. Excessive flow at high pressures leads to a high amount of turbulence and splashing at the cutting zone causing uneven machining at the point of contact as the feed and speed rates are increased.[3] In the jet application, a hydraulic pump pressurizes the cutting fluid required for the machining cycle at 24 Mpa. This process when compared to flood cooling has an advantage of penetrating the area of machining especially in the area of chip–tool interface where the tool comes in contact with the workpiece during the machining cycle.[2] In mist applications, small droplets of cutting fluids are dispersed in the form of a gaseous medium at the clearance crevice in the cutting zone. The major significance of this method is it combines both properties of liquid and gas ensuring a larger surface to volume ratio for every droplet enhancing quick heat release through continuous vaporization with low quantity of coolant consumption. The small size of the droplet also ensures better penetration ability of the cutting fluid, spillage is kept at bare minimum and the chips are washed away continuously during the machining cycle.[2,4,7]