Question: Mild steel is being machined at a cutting speed of 200 m/min with a tool rake angle of 10°. The width of cut and uncut thickness are 2 mm and 0.2 mm, respectively. If the average value of co‐efficient of friction between the tool and the chip is 0.5 and the shear stress of the work material is 400 N/mm2, then determine: [ESE 2005] (i) The shear angle (ii)
Question: In orthogonal turning of an engineering alloy, it has been observed that the friction force acting at the chip-tool interface is 402.5 N and the friction force is also perpendicular to the cutting velocity vector. The feed velocity is negligibly small with respect to the cutting velocity. The ratio of friction force to normal force associated with the chip‐tool interface is 1. The uncut chip thickness is 0.2 mm
Question: Details pertaining to an orthogonal metal cutting process are given below. Chip thickness ratio = 0.4 Undeformed thickness = 0.6 mm Rake angle = +10° Cutting speed = 2.5 m/s Mean thickness of primary shear zone 25 microns. Determine shear strain rate in s–1 during the process. [GATE 2012] Solution: During machining, as the cutting tool compresses a layer of material, it gets sheared off in the form of
Question: An orthogonal cutting operation is being carried out under the following conditions: Cutting speed = 2 m/s Depth of cut = 0.5 mm Chip thickness = 0.6 mm Calculate the chip velocity. [ESE 2003] Solution: To solve this question we need to assume two things—(i) orthogonal rake angle (γO) of the cutting tool is 0° as it is the case of orthogonal cutting, and (ii) the given depth of
Question: An orthogonal turning operation is carried out at 20m/min cutting speed, using a cutting tool of rake angle 15°. The chip thickness is 0.4mm and the uncut chip thickness is 0.2mm. Determine (i) the shear plane angle in degrees, and (ii) the chip velocity in m/min. [GATE 2009] Answer: In conventional machining the workpiece material is removed by shearing as and when the cutting tool compresses it. For simplicity
Question: The rake angle of a cutting tool is 15°, shear angle 45° and cutting velocity 35m/min. What is the velocity of chip along the tool face? [ISRO 2009] Answer: Three velocity terms namely cutting velocity (VC), chip flow velocity (Vf) and shear velocity (VS) are associated with orthogonal machining of ductile material using a sharp cutting tool. These three velocity terms together constitute a vector triangle, which is also
Question: In an orthogonal cutting, the depth of cut is halved and the feed rate is made double. If the chip thickness ratio is unaffected with the changed cutting conditions, what will be the change in actual chip thickness? [IAS 1995] Solution: Chip thickness ratio, also called cutting ratio (rcu), is one important parameter for machining analysis as it indicates the deformation (elongation) of chip in its thickness. Machining is
Question: If α is the rake angle of the cutting tool, φ is the shear angle and V is the cutting velocity, then express the velocity of chip sliding along the shear plane in terms of above three parameters. [ESE 2001] Answer: To solve this question, one need the knowledge of velocity triangle in machining. In an orthogonal machining of ductile material with a sharp cutting tool, three velocity parameters
Question: In a pure orthogonal turning process, the chip thickness is 0.32mm, feed is 0.2 mm/rev. What is the cutting ratio? [ESE 2014] Solution: The ratio between the uncut chip thickness (a1) to the chip thickness (a2) is termed as cutting ratio (rcu). Owing to lamellar shearing and positive strain, the chip thickness increases as compared to the same for uncut chip. Thus cutting ratio is smaller tan 1, especially
Question: In an orthogonal cutting operation, the tool has a rake angle of 10°. The chip thickness before the cut is 0.5mm and the cut yields a deformed chip thickness of 1.125 mm. Calculate (i) shear plane angle, and (ii) shear strain for the operation. [IAS 2015] Solution: During machining, the excess material is gradually removed in the form of chip by shearing only. Although shearing takes place over a
