METAL CUTTING AND MACHINE TOOLS 11th LECTURE: TOOL WEAR AND TOOL LIFE ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING IIT KHARAGPUR

1

TOOL WEAR AND TOOL LIFE A cutting tool is susceptible to breakage, dulling and wear

Rake           surface Aux.    flank

Pr. flank

ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 2 IIT KHARAGPUR

TOOL WEAR AND TOOL LIFE

Flank wear growth,  mm

A cutting tool is susceptible to breakage, dulling and wear

Rake           surface Aux.    flank

Pr. flank

Machining time, mins ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 3 IIT KHARAGPUR

TOOL WEAR AND TOOL LIFE

Flank wear growth,  mm

Cutting velocity, m/min

A cutting tool is susceptible to breakage, dulling and wear

Machining time, mins

Tool life, mins ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 4 IIT KHARAGPUR

METAL CUTTING AND MACHINE TOOLS 12th LECTURE: WEAR AND LIFE OF CUTTING TOOLS - 2 ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING IIT KHARAGPUR

1

WEAR AND LIFE OF CUTTING TOOLS - 2 In a machine shop, single point turning tools are used at 75m/min to yield a  tool life of 30 min. However, war breaks out and the turning tools have to be  used at 100 m/min to yield a tool life of 20 mins. Last of all, the machine shop  passes onto the hand of the enemy army, who start running the tools at  speed of 125 m/min. They will get a tool life nearest to  

a. 1 min           b. 10 mins

c. 15 mins

d. None of these          

ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 2 IIT KHARAGPUR

WEAR AND LIFE OF CUTTING TOOLS - 2 Find the value of n = 0.709 Find the value of C = 836.25 Find the value of T3 = 14.595 mins

V1  T1n  V2  T2n 75  30

V3  T

0.709 3

a. 1 min           b. 10 mins

c. 15 mins

0.709

 C  836.25

 125  T

0.709 3

 836.25

d. None of these          

ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 3 IIT KHARAGPUR

WEAR AND LIFE OF CUTTING TOOLS - 2 The following data is received for a new carbide tool machining  low carbon steel. Determine the n and C of the Taylor’s tool life  equation given as below 

VT  C n

V(m/min)

40

50

60

70

80

T (min)

40

32

26

20

17

ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 4 IIT KHARAGPUR

WEAR AND LIFE OF CUTTING TOOLS - 2

VT  C ln V  n  ln T  ln C

ln(V)

n

ln(T) V(m/min)

40

50

60

70

80

T (min)

40

32

26

20

17

ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 5 IIT KHARAGPUR

ln(V)

WEAR AND LIFE OF CUTTING TOOLS - 2

ln(T) ln(V)

3.688

3.912

4.094

4.248

4.382

ln(T)

3.688

3.465

3.258

2.995

2.833

ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 6 IIT KHARAGPUR

ln(V)

WEAR AND LIFE OF CUTTING TOOLS - 2

n = 0.7886 ln(C) = 6.6269 C = 755.141

ln(T) ln(V)

3.688

3.912

4.094

4.248

4.382

ln(T)

3.688

3.465

3.258

2.995

2.833

ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 7 IIT KHARAGPUR

ASIMAVA ROY CHOUDHURY MECHANICAL ENGG 8 IIT KHARAGPUR

METAL CUTTING AND MACHINE TOOLS 13th LECTURE: THE LATHE ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING IIT KHARAGPUR

1

THE LATHE

Work piece

Generally, the workpiece rotates and  cutter moves relative to the workpiece

C/T

Quick notes : Chuck,  tool post, compound  slide, face plate, centre

Work holding Chuck

The lathe is a machine tool on which surfaces of revolution  can be produced. 

Feed

ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 2 IIT KHARAGPUR

THE LATHE Work piece and cutting tool need to be held rigidly  Motor

Speed  gear  box

Quick notes : Gear box,  motor, lead screw, half  nut

Lead screw

And they have to be provided some motions relative to  each other  ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 3 IIT KHARAGPUR

THE LATHE The cutting tool is mounted on a tool post which is part of a moving member  called  carriage (top  saddle) Saddle Speed  gear  Motor box

Tool post

The work piece is rotated by means of a motor through a  speed gear box  ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 4 IIT KHARAGPUR

THE LATHE A tail stock may support  the rear end of w/p Motor

Speed  gear  box

Or it may hold drills or drill chuck,  be offset for taper turning

Tail stock

Quick notes : Lathe  bed, guideways

ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 5 IIT KHARAGPUR

LATHE AND MILLING MACHINES Gear boxes – how do they  work ? Input 

Intermediate  Output 

There are sliding clusters inside the gear box which may be  slid into meshing position with gears on other shafts ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 6 IIT KHARAGPUR

THE LATHE The carriage: it is simply a  car…  Rack

Feed Rod worm

Input power comes to the carriage may come through the  lead screw or feed rod ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 7 IIT KHARAGPUR

METAL CUTTING AND MACHINE TOOLS 14th LECTURE: CALCULATIONS PERTAINING TO MACHINE TOOLS ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING IIT KHARAGPUR

1

Calculations pertaining to machine tools  Gear calculations  Gears have been represented in a  simplified form. Zi represents the  number of teeth of ith Gear. Gear  1 drives the train by rotating at  40 rpm. The rpm of the gear 5 in  the gear train shown will be                     nearest to 1600 400 800 200

Gear 1 Z1 = 210 40 rpm

Gear 5 Gear 4

Z4= 87

Z4= 42

Gear 3 Z3= 84 Gear 2 Z2= 42 Fig. 2

ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 2 IIT KHARAGPUR

Calculations pertaining to machine tools  Gear calculations  A motor drives the train at 1440  rpm. Zwg refers to number of  teeth on the worm gear in  connection with worm. The  speed of the rack in m/min will  be nearest to 60.652 28.893 14.476 5.324 None of the others

Worm, k = 2 Motor 

Gear B

1440 rpm

Z = 30 Zwg =40 Rack, module=2 mm

Fig. 3 Gear A Z = 32

ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 3 IIT KHARAGPUR

Calculations pertaining to machine tools  Screw thread calculations  Number of starts

Pitch and lead

ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 4 IIT KHARAGPUR

METAL CUTTING AND MACHINE TOOLS 15th LECTURE: NUMERICAL PROBLEMS ON LATHE ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING IIT KHARAGPUR

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LATHE On a lathe, a cylindrical work piece of 100 mm diameter is being turned.  The RPM is 100. The cutting speed is nearest to (m/min)

V

  D N 1000

a. 31.41        b. 3.141          c. 314.1         d. None of these 

ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 2 IIT KHARAGPUR

LATHE On a lathe, a cylindrical work piece of 100 mm diameter is being turned.  The RPM is 100. The length of the work piece is 200 mm. The feed is 0.2  mm/rev. Ignoring approach and overtravel, the machining time for one  pass will be nearest to (in min) T

L s0  N

T

  D L 1000  s0  V

T

  D   D1  D2   L 2000  s0  t  V

a. 10         b. 20          c. 5         d. None of these 

ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 3 IIT KHARAGPUR

LATHE On a lathe, a cylindrical work piece of 100 mm diameter is being turned.  The RPM is 100. The length of the work piece is 200 mm. The feed is 0.2  mm/rev. The depth of cut is 2 mm. The material removal rate will be 

MRR  V  s  t a. 10         b. 20          c. 5         d. None of these 

ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 4 IIT KHARAGPUR

LATHE METRIC PITCHES CUT ON THE LATHE 0.4

0.45

0.5

5.5

5.75

6

0.8

0.9

1.0

1.1

1.15

1.2

1.6

1.8

2.0

2.2

2.3

2.4

3.2

3.6

4.0

4.4

4.6

4.8

ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 5 IIT KHARAGPUR

LATHE METRIC PITCHES CUT ON THE LATHE 0.4

0.45

0.5

0.55

0.6

0.65

0.8

0.9

1.0

1.1

1.2

13

1.6

1.8

2.0

2.2

2.4

26

3.2

3.6

4.0

4.4

4.8

52

INCH THREADS CUT ON THE LATHE (TPI) 4

4.5

5

5.5

6

6.5

8

9

10

11

12

13

16

18

20

22

24

26

32

36

40

44

48

52

ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 6 IIT KHARAGPUR

LATHE FEED DRIVE Motor

SGB

Norton –Tumbler sets 24 METRIC PITCHES CUT ON THE LATHE

2

2.25

2.5

2.75

3

4

4.5

5

5.5

6

8

9

10

11

12

To 6 mm  lead screw

ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 7 IIT KHARAGPUR

LATHE FEED DRIVE Motor

SGB

To 6 mm  lead screw 21

Norton –Tumbler sets

42

21

24 METRIC PITCHES CUT ON THE LATHE

0.4

0.45

0.5

5.5

0.6

0.8

0.9

1.0

1.1

1.2

1.6

1.8

2.0

2.2

2.4

3.2

3.6

4.0

4.4

4.8

21

42

ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 8 IIT KHARAGPUR

LATHE Motor

SGB

Norton –Tumbler  Arrangement

ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING 9 IIT KHARAGPUR

Lathe feed drives – the meander drive 21

42

21

42

18

42

21

42

21

45

21

21

42

42

21

ASIMAVA ROY CHOUDHURY MECHANICAL ENGINEERING IIT KHARAGPUR 10

Week 3 Lecture Material.pdf

Page 2 of 33. 2. ASIMAVA ROY CHOUDHURY. MECHANICAL ENGINEERING. IIT KHARAGPUR. A cutting tool is susceptible to breakage, dulling and wear. TOOL WEAR AND TOOL LIFE. Rake. surface. Pr. flank. Aux. flank. Page 2 of 33. Page 3 of 33. 3. ASIMAVA ROY CHOUDHURY. MECHANICAL ENGINEERING.

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