Question Paper 2.pdf

Model Question Paper-2 Full Marks: 100

Time: 3 Hours

 Answer all the questions of Group-A and six more questions taking any three from Group-B and any three from Group-C.

Group-A  Q1

Select the correct correct answer from the given given four options: (1 × 10 = 10) (i) Productivity is assessed by material removal rate (MRR) in (a) rolling operations (b) welding operations (c) machining operations (d) casting work  (ii) Rake angle of the cutting tool is the angle of inclination of the tool rake surface from that tool’s (a) reference plane (b) orthogonal plane (c) normal plane (d) cutting plane (iii) Life of turning tools is maximum affected by increase of  (a) cutting velocity (b) tool feed rate (c) depth of cut (d) width of cut (iv) The amount of actual machining time in any turning operation depends upon (a) cutting velocity (b) feed (c) depth of cut (d) all of the above (v) Chip-breaker is essentially employed in turning rods of  (a) mild steel at low cutting velocity  (b) mild steel at high cutting velocity  (c) cast iron at low cutting velocity  (d) cast iron at high cutting velocity  (vi) The letter ‘K’ in the specification of a grinding wheel A60 K 8V indicates (a) abrasive type (b) porosity of the wheel (c) bond material of the wheel (d) grade of strength of the wheel

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Machining and Machine Tools

(vii)

The workpiece always rotates during machining in (a) lathes (b) drilling machines (c) boring machines (d) milling machines (viii) Quick return effect is provided in (a) shaping machine (b) gear shaping machine (c) slotting machine (d) broaching machine (ix) CNC milling machines are (a) non-automatic (b) semi-automatic (c) fixed type automatic (d) flexibly automatic (x) In machine tools, error and inaccuracy are (a) independent (b) same (c) interdependent (d) totally different

Group-B Q2 Q3

Q4

Q5 Q6

(a) (b) (a) (b) (a) (b) (a) (b) (a) (b)

What items are essentially required to produce a job by machining? How can the industries increase their profit in manufacturing by machining? (5 + 5) State the purposes of determination of the magnitude of the cutting forces. What are the possible harmful effects of the high cutting temperature on the cutting tools (5 + 5) and workpieces? Compare the two tool materials – HSS and sintered carbide w.r.t. their composition and applications. How are centre lathes specified? (5 + 5) How is feed expressed in turning, drilling, shaping, milling and broaching? Where and why a rack is fitted in centre lathes? (5 + 5) What are the advantages of flexible automation over fixed (or hard) automation in respect of machine tools? (5 + 5) State the purposes of using jigs and fixtures in manufacturing by machining.

Group-C Q7

(a) (b)

Q8

(a)

Schematically draw a single point turning tool and show its different rake angles, clearance angles and the cutting edge angles. What are the benefits of making the flutes (cutting edges) of plain milling cutters helical? (16 + 4) During straight turning of a mild steel rod by a tool of geometry: 0°, 10°, 7°, 6°, 15°, 60°, 0 (mm) at feed of 0.20 mm/rev, the following observations were made:

Model Question Paper-2

tangential component (P z) of the cutting force = 800 N • axial component (P  ) of the cutting force = 400 N x  • chip thickness (a  ) = 0.40 mm 2 Determine the value of apparant coefficient of friction that occurred at the chip–tool interface under that machining condition. Why are conventional milling machines provided with large number of spindle (arbour) (12 + 8) speeds? During turning a steel rod by a carbide tool insert, the life of the cutting edges increased from 10 min to 20 min, when only the cutting velocity was reduced from 200 m/min to 150 m/min. If another fresh cutting edge of that tool insert is used under the same condition but at 180 m/min of cutting velocity, then how much would be the life (min) of that cutting edge? State the relative advantages and limitations of hydraulic drive over conventional electromechanical drive in machine tools. (12 + 8) Distinguish between open-loop control and closed-loop control being employed for feed motions of the worktable in CNC machine tools, in respect of principle and application. Describe briefly with the help of a suitable sketch how the longitudinal feed motion of the cutting tool is derived (obtained) from the rotation of the feed rod in a centre lathe. (10 + 10) State the procedural steps to be followed in sequence while designing the foundation of any machine tool. Write a manual part program for drilling a hole of diameter 10 mm at the centre of a premachined brass plate of dimensions 120 × 100 × 8 mm in a CNC drilling machine. (8 + 12) •

(b) Q9

(a)

(b) Q10

(a) (b)

Q11

(a) (b)

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