59920082 Force Power In Metal Cutting

7/13/2011

ESE‐2003‐ Conventional

Force & Power in Metal Cutting

By  S K Mondal Compiled by: S K Mondal           Made Easy

During turning a carbon steel rod of 160 mm diameter by a carbide tool of geometry; 0, 0, 10, 8, 15, 75, 0 (mm) at speed of 400 rpm, feed of 0.32 mm/rev and 4.0 mm depth of cut, the following observation were made. Tangential component of the cutting force, Pz = 1200 N Axial component of the cutting force, force Px = 800 N Chip thickness (after cut),α 2 = 0.8 mm. For the above machining condition determine the values of (i) Friction force, F and normal force, N acting at the chip tool interface. (ii) Yield shears strength of the work material under this machining condition. (iii) Cutting power consumption in kW. Compiled by: S K Mondal           Made Easy Ans F = 800 N N = 1200 N 256 7 Mpa 4 021 KW

GATE – 1995 ‐Conventional

ESE ‐2000 (Conventional)

While turning a C‐15 steel rod of 160 mm diameter at 315 rpm, 2.5 mm depth of cut and feed of 0.16 mm/rev by a tool of geometry 00, 100, 80, 90,150, 750, 0(mm), the following observations were made. Tangential component of the cutting force = 500 N Axial component of the cutting force = 200 N Chip thickness = 0.48 mm Draw schematically the Merchant’s circle diagram for the cutting force in the present case. Ans. F = 284 N, N = 457.67 N, Fn = 348.78 N, Fs = 410.31 N Friction angle =Compiled by: S K Mondal           Made Easy 32o

The following data from the orthogonal cutting test is available. Rake angle = 100, chip thickness ratio = 0.35, uncut chip thickness = 0.51, width of cut = 3 mm, yield stress of work material = 285 N/mm2, 5, mean friction co‐efficient on tool force = 0.65, Determine (i) Cutting force (Fc) (ii) Radial force (Ft) (iii) Normal force (N) on tool and (iv) Shear force on the tool (Fs ). Ans. Fc = 1597 N; Ft = 678 N; Fs = 1265 N; F = 944.95 N, N = 1453.8 N Compiled by: S K Mondal           Made Easy

ESE‐2005 Conventional

IAS‐2003 Main Examination

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. p y If the average g 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, Determine (i) shear angle and [Ans. 36.7o (ii) Cutting and thrust component of the machine on force. [Ans. Fc = 420 N, Ft = 125 N ]

During turning process with 7 ‐ ‐ 6 – 6 – 8 – 30 – 1 (mm) ASA tool the undeformed chip thickness of 2.0 mm and width of cut of 2.5 mm were used. The side rake angle of the tool was a chosen that the machining operation could be approximated to be orthogonal cutting. cutting The tangential cutting force and thrust force were 1177 N and 560 N respectively. Calculate: [30 marks] (i) The side rake angle [Ans. 12o ] (ii) Co‐efficient of friction at the rake face [Ans. 0.82] (iii) The dynamic shear strength of the work material [Ans. 74.43 Mpa] Compiled by: S K Mondal           Made Easy

Compiled by: S K Mondal           Made Easy

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7/13/2011

GATE‐2006 Common Data Questions(1) In an orthogonal machining operation: Uncut thickness = 0.5 mm  Cutting speed = 20 m/min  Rake angle = 15° Width of cut   5 mm  Chip thickness   0.7 mm Width of cut = 5 mm  Chip thickness = 0.7 mm Thrust force = 200 N  Cutting force = 1200 N Assume Merchant's theory. The coefficient of friction at the tool‐chip interface is    (a) 0.23  (b) 0.46  (c) 0.85  (d) 0.95 Ans. (b) Compiled by: S K Mondal           Made Easy

GATE‐2006 Common Data Questions(3) In an orthogonal machining operation: Uncut thickness = 0.5 mm  Cutting speed = 20 m/min  Rake angle = 15° Width of cut  Width of cut = 5 mm   5 mm  Chip thickness  Chip thickness = 0.7 mm  0.7 mm Thrust force = 200 N  Cutting force = 1200 N Assume Merchant's theory. The values of shear angle and shear strain,  respectively, are                   (a) 30.3° and 1.98  (b) 30.3° and 4.23  (c) 40.2° and 2.97  (d) 40.2° and 1.65          Ans. (d) Compiled by: S K Mondal           Made Easy

GATE‐2003 Common Data Questions(2) A cylinder is turned on a lathe with orthogonal machining principle. Spindle rotates at 200 rpm. The axial feed rate is 0.25 mm per revolution. Depth of cut is 0.4 mm. The rake angle is 10°. In the analysis it is found that th t the th shear h angle l is i 27.75°° In the above problem, the coefficient of friction at  the chip tool interface obtained using Earnest and  Merchant theory is     (a) 0.18  (b) 0.36  (c) 0.71  (d) 0.908 Ans. (d) Compiled by: S K Mondal           Made Easy

GATE‐2006 Common Data Questions(2) In an orthogonal machining operation: Uncut thickness = 0.5 mm  Cutting speed = 20 m/min  Rake angle = 15° Width of cut   5 mm  Chip thickness   0.7 mm Width of cut = 5 mm  Chip thickness = 0.7 mm Thrust force = 200 N  Cutting force = 1200 N Assume Merchant's theory. The percentage of total energy dissipated due to  friction at the tool‐chip interface is  (a) 30%  (b) 42%  (c) 58%  (d) 70% Ans. (a) Compiled by: S K Mondal           Made Easy

GATE‐2003 Common Data Questions(1) A cylinder is turned on a lathe with orthogonal machining principle. Spindle rotates at 200 rpm. The axial feed rate is 0.25 mm per revolution. Depth of cut is 0.4 mm. The rake angle is 10°. In the analysis it is found th t the that th shear h angle l is i 27.75°° The thickness of the produced chip is (a) 0.511 mm  (b) 0.528 mm  (c) 0.818 mm (d) 0.846 mm Ans. (a) Compiled by: S K Mondal           Made Easy

GATE‐2008 Common Data Question (1) Orthogonal turning is performed on a cylindrical work piece with shear strength of 250 MPa. The following conditions are used: cutting velocity is 180 m/min. feed is 0.20 mm/rev. depth of cut is 3 mm. chip thickness ratio ti = 0.5. The Th orthogonal th l rake k angle l is i 7o. Apply A l Merchant's theory for analysis. The shear plane angle (in degree) and the shear  force respectively are  (a) 52: 320 N (b) 52: 400N      (c) 28: 400N     (d) 28:320N  Ans. (d) Compiled by: S K Mondal           Made Easy

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7/13/2011

GATE‐2008 Common Data Question (2) Orthogonal turning is performed on a cylindrical work piece with shear strength of 250 MPa. The following conditions are used: cutting velocity is 180 m/min. feed is 0.20 mm/rev. depth of cut is 3 mm. chip thickness ratio ti = 0.5. The Th orthogonal th l rake k angle l is i 7o. Apply A l Merchant's theory for analysis. The cutting and frictional forces, respectively, are        (a) 568N; 387N        (b) 565N; 381N       (c) 440N; 342N (d) 480N; 356N Ans. (b) 

IES 2010 The relationship between the shear angle Φ, the friction angle β and cutting rake angle α is given as

Ans. (b) 

Compiled by: S K Mondal           Made Easy

Compiled by: S K Mondal           Made Easy

IES‐2005 Which one of the following is the correct expression for the Merchant's machinability constant? (a) 2φ + γ − α (b) 2φ − γ + α (c) 2φ − γ − α (d) φ + γ − α (Where φ = shear angle,γ = friction angle andα = rake angle) Ans. (a)

GATE‐1997 In a typical metal cutting operation, using a  cutting tool of positive rake  angle = 10°, it  was observed that the shear angle was 20°.  The friction angle is         g (a) 45° (b) 30° (c) 60° (d) 40° Ans. (c)

Compiled by: S K Mondal           Made Easy

Compiled by: S K Mondal           Made Easy

IAS – 1999 In an orthogonal cutting process, rake angle of the tool is 20° and friction angle is 25.5°. Using Merchant's shear angle relationship, the value of shear angle will be (a) 39.5 39 5° (b) 42.25 42 25° (c) 47.75° (d) 50.5°

IES‐2003 In orthogonal cutting test, the cutting force = 900 N, the thrust force = 600 N and chip shear angle is 30o. Then the chip shear force is (a) 1079.4 1079 4 N (b) 969.6 969 6 N (c) 479.4 N (d) 69.6 N Ans. (c)

Ans. (b) Compiled by: S K Mondal           Made Easy

Compiled by: S K Mondal           Made Easy

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IES‐2000

IES‐1996

In an orthogonal cutting test, the cutting force and thrust force were observed to be 1000N and 500 N respectively. If the rake angle of tool is zero, the coefficient of friction in chip‐tool interface will be 1

(a) 2                

( b) 2         

( c) 

1

                       ( d) 2         2

Ans. (a) Compiled by: S K Mondal           Made Easy

Which of the following forces are measured directly by strain gauges or force dynamometers during metal cutting ? 1. Force exerted by the tool on the chip acting normally to the tool face. 2. Horizontal cutting force exerted by the tool on the work piece. 3. Frictional resistance of the tool against the chip flow acting along the tool face. 4. Vertical force which helps in holding the tool in position. (a) 1 and 3 (b) 2 and 4 (c) 1 and 4 (d) 2 and 3 Ans. (b) Compiled by: S K Mondal           Made Easy

GATE‐2007 In orthogonal turning of medium carbon steel. The  specific machining energy is 2.0 J/mm3. The cutting  velocity, feed and depth of cut are 120 m/min, 0.2  mm/rev and 2 mm respectively. The main cutting  force in N is f  i  N i (a) 40  (b) 80  (c) 400  (d) 800

GATE‐2007 In orthogonal turning of low carbon steel pipe with principal cutting edge angle of 90°, the main cutting force is 1000 N and the feed force is 800 N. The shear angle is 25° and orthogonal rake angle is zero. E Employing l i M h t’ theory, Merchant’s th th ratio the ti off friction f i ti force to normal force acting on the cutting tool is (a) 1.56 (b) 1.25 (c) 0.80 (d) 0.64

Ans. (d) Ans. (c) Compiled by: S K Mondal           Made Easy

Compiled by: S K Mondal           Made Easy

IES‐1997 Consider the following forces acting on a finish turning tool: 1. Feed force 2. 2 Thrust force 3. Cutting force. The correct sequence of the decreasing order of the magnitudes of these forces is (a) 1, 2, 3 (b) 2, 3, 1 (c) 3, 1, 2 (d) 3, 2, 1 Ans. (c) Compiled by: S K Mondal           Made Easy

IES‐1999 The radial force in single‐point tool during turning operation varies between (a) 0.2 to 0.4 times the main cutting force (b) 0.4 0 4 to 0.6 0 6 times the main cutting force (c) 0.6 to 0.8 times the main cutting force (d) 0.5 to 0.6 times the main cutting force Ans. (a) Compiled by: S K Mondal           Made Easy

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IES‐1995 The primary tool force used in calculating the total power consumption in machining is the (a) Radial force (b) Tangential force (c) Axial force (d) Frictional force

IES‐2002 In a machining process, the percentage of heat carried away by the chips is typically (a) 5% (b) 25% (c) 50% (d) 75% 0% % Ans. (d)

Ans. (b)

Compiled by: S K Mondal           Made Easy

Compiled by: S K Mondal           Made Easy

IAS – 2003

IES‐1998 In metal cutting operation, the approximate ratio of heat distributed among chip, tool and work, in that order is (a) 80: 10: 10 (b) 33: 33: 33 (c) 20: 60: 10 (d) 10: 10: 80 Ans. (a)

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As the cutting speed increases (a) More heat is transmitted to the work piece and less  heat is transmitted to the tool (b) More heat is carried away by the chip and less heat is  t transmitted to the tool itt d t  th  t l (c) More heat is transmitted to both the chip and the  tool (d) More heat is transmitted to both the work piece and  the tool Ans. (b)

IAS – 1995

IES‐2001 Power consumption in metal cutting is mainly due to (a) Tangential component of the force (b) Longitudinal component of the force (c) Normal component of the force (d) Friction at the metal‐tool interface

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Thrust force will increase with the increase in (a) Side cutting edge angle (b) Tool nose radius   (c) Rake angle (d) End cutting edge angle Ans. (a)

Ans. (a) Compiled by: S K Mondal           Made Easy

Compiled by: S K Mondal           Made Easy

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IES 2010 Consider the following statements: In an orthogonal, single‐point metal cutting, as the side‐cutting edge angle is increased, g 1. The tangential force increases. 2. The longitudinal force drops. 3. The radial force increases. Which of these statements are correct? (a) 1 and 3 only (b) 1 and 2 only (c) 2 and 3 only (d) 1, 2 and 3 Ans. (c)

IES‐1993 A 'Dynamometer' is a device used for the measurement of (a) Chip thickness ratio (b) Forces during metal cutting (c) Wear of the cutting tool (d) Deflection of the cutting tool Ans. (b)

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IES 2011 The instrument or device used to measure the cutting  forces in machining is : (a) Tachometer (b) Comparator (c) Dynamometer (d) Lactometer

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IAS – 2003 The heat generated in metal conveniently be determined by (a) Installing thermocouple on the job (b) Installing thermocouple on the tool (c) Calorimetric set‐up (d) Using radiation pyrometer

cutting

can

Ans. (c)

Ans. (c)

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IES‐1998 The gauge factor of a resistive pick‐up of cutting force dynamometer is defined as the ratio of (a) Applied strain to the resistance of the wire (b) The proportional change in resistance to the applied strain (c) The resistance to the applied strain (d) Change in resistance to the applied strain Ans. (b) Compiled by: S K Mondal           Made Easy

Compiled by: S K Mondal           Made Easy

IES‐2000 Assertion (A): In metal cutting, the normal laws of sliding friction are not applicable. Reason (R): Very high temperature is produced at the tool‐chip interface. interface (a) Both A and R are individually true and R is the correct explanation of A (b) Both A and R are individually true but R is not the correct explanation of A (c) A is true but R is false (d) A is false but R is true Ans. (b) Compiled by: S K Mondal           Made Easy

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GATE 1992 The effect of rake angle on the mean friction angle in machining can be explained by (A) sliding (Coulomb) model of friction (B) sticking and then sliding model of friction (C) sticking friction (D) Sliding and then sticking model of friction

Ans. (b) Compiled by: S K Mondal           Made Easy

IES‐2004 Assertion (A): The ratio of uncut chip thickness to actual chip thickness is always less than one and is termed as cutting ratio in orthogonal cutting Reason (R): The frictional force is very high due to the g friction rather than sliding g occurrence of sticking friction (a) Both A and R are individually true and R is the correct explanation of A (b) Both A and R are individually true but R is not the correct explanation of A (c) A is true but R is false (d) A is false but R is true

Compiled by: S K Mondal           Made Easy

Ans. (b)

GATE‐1993 The effect of rake angle on the mean friction angle in machining can be explained by (a) Sliding (coulomb) model of friction (b) sticking g and then siding g model of friction (c) Sticking friction (d) sliding and then sticking model of friction

Ans. (d) Compiled by: S K Mondal           Made Easy

Compiled by: S K Mondal           Made Easy

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