ME364_machining_turning

# ME364_machining_turning - 6 MACHINING OPERATIONS CHAPTER...

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CHAPTER CONTENTS 93 6 MACHINING OPERATIONS 6.1 Turning 6.2 Milling 6.3 Drilling and Reaming 6.4 Planing, Shaping and Broaching 6.5 Boring 6.6 Gear Manufacturing Introduction Turning is a machining process to produce parts round in shape by a single point tool on lathes . The tool is fed either linearly in the direction parallel or perpendicular to the axis of rotation of the workpiece, or along a specified path to produce complex rotational shapes. The primary motion of cutting in turning is the rotation of the workpiece, and the secondary motion of cutting is the feed motion. Cutting conditions in turning Cutting speed in turning V in m/s is related to the rotational speed of the workpiece by the equation: V = π DN where D is the diameter of the workpiece, m; N is the rotational speed of the workpiece, rev/s. direction of feed motion tool workpiece machined surface work surface transient surface chip direction of primary motion f d D D o f Turning operation 6.1 TURNING

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Turning 94 Valery Marinov, Manufacturing Technology One should remember that cutting speed V is always a linear vector. In the process planning of a turning operation, cutting speed V is first selected from appropriate reference sources or calculated as discussed in Section 5.10 Selection of Cutting Conditions , and the rotational speed N is calculated taking into account the workpiece diameter D. Rotational speed, not cutting speed, is then used to adjust lathe setting levers. Feed in turning is generally expressed in mm tr -1 (millimetres per revolution). The turning operation reduces the diameter of the workpiece from the initial diameter D o to the final diameter D f . The change in diameter is actually two times depth of cut , d: 2d = D o - D f The volumetric rate of material removal (so-called material removal rate , mrr ) is defined by mrr = Vfd When using this equation, care must be exercised to assure that the units for V are consistent with those for f and d. Operations in turning Turning is not a single process but class of many and different operations performed on a lathe. Turning of cylindrical surfaces The lathe can be used to reduce the diameter of a part to a desired dimension. The resulting machined surface is cylindrical. V f V f f V facing tube turning parting (cutting-off) Turning of flat surfaces A lathe can be used to create a smooth, flat face very accurately perpendicular to the axis of a cylindrical part. Tool is fed radially or axially to create a flat machined surface. V f V f straight turning plunge turning Threading Different possibilities are available to produce a thread on a lathe. Threads are cut using lathes by advancing the cutting tool at a feed exactly equal to the thread pitch. The single-point cutting tool cuts in a helical band, which is actually a thread. The procedure calls for correct settings of the machine, and also that the helix be restarted at the same location each time if multiple passes are required to cut the entire depth of thread. The tool point must be ground so that it has the same profile as the thread to be cut.
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• Lathe, Screw machine, Lathes, Valery Marinov

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