486. Taylor’s tool life equation is given by VTⁿ = C, where V is in m/min and T is in min. In a turning operation, two tools X and Y are used. For tool X, n = 0.3 and C = 60 and for tool Y, n = 0.6 and C = 90. Both the tools will have the same tool life for the cutting speed (in m/min, round off one decimal place) of ______.

1. 1. 50 m/min

   
   
   

   2. 40 m/min

   
   
   

   3. 45 m/min

   
   
   

   4. 41 m/min

   
   
   

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   Taylor’s tool life equation,
   VTⁿ = c
   for Tool X, for Tool y
   VT^0.3 = 60 VT^0.6 = 90
   Velocity when both tools have same tool life.
   

   VT0.3	=	60
   VT0.6		90

   
   

   (T)0.6 − 0.6 =	6
   	9

   
   T^0.3 = 1.5
   T = (1.5)^1/0.3min
   

   V =	60	= 40 m/min
   	(1.5)0.3/0.3

   Correct Option: B

   Taylor’s tool life equation,
   VTⁿ = c
   for Tool X, for Tool y
   VT^0.3 = 60 VT^0.6 = 90
   Velocity when both tools have same tool life.
   

   VT0.3	=	60
   VT0.6		90

   
   

   (T)0.6 − 0.6 =	6
   	9

   
   T^0.3 = 1.5
   T = (1.5)^1/0.3min
   

   V =	60	= 40 m/min
   	(1.5)0.3/0.3

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487. Taylor's tool life equation is used to estimate the life of a batch of identical HSS twist drills by drilling through holes at constant feed in 20 mm thick mild steel plates. In test 1, a drill lasted 300 holes at 150 rpm while in test 2, another drill lasted 200 holes at 300 rpm.
     The maximum number of holes that can be made by another drill from the above batch at 200 rpm is (correct to two decimal places).

1. 1. 25353

   
   
   

   2. 154.54

   
   
   

   3. 253.53

   
   
   

   4. None of the above

   
   
   

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1. View Hint View Answer Discuss in Forum

   Number of holes can be drilled = 253.53

   Correct Option: C

   Number of holes can be drilled = 253.53

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488. Feed rate in slab milling operation is equal to

1. 1. rotation per minute (rpm)

   
   
   

   2. product of rpm and number of teeth in the cutter

   
   
   

   3. product of rpm, feed per tooth and number of teeth in the cutter

   
   
   

   4. product of rpm, feed per tooth and number of teeth in contact

   
   
   

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1. View Hint View Answer Discuss in Forum

   Table feed or Feed rate
   

   Correct Option: C

   Table feed or Feed rate
   

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489. The preferred option for holding an odd-shaped workpiece in a centre lathe is

1. 1. live and dead centres

   
   
   

   2. three jaw chuck

   
   
   

   3. lathe dog

   
   
   

   4. four jaw chuck

   
   
   

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1. View Hint View Answer Discuss in Forum

   4 jaw Chuck

   Correct Option: D

   4 jaw Chuck

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490. An orthogonal cutting operations is being carried out in which uncut thickness is 0.010 mm, cutting speed is 130 m/min, rake angle is 15° and width of cut is 6 mm. It is observed that the chip thickness is 0.015 mm, the cutting force is 60 N and the thrust force is 25 N. The ratio of friction energy to total energy is ______. (correct to two decimal places)

1. 1. 0.4408

   
   
   

   2. 1.44

   
   
   

   3. 0.9938

   
   
   

   4. None of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   t = 0.010 mm
   v = 130 m/min
   α = 15°
   b = 6 mm
   t_c = 0.015 mm
   F_c = 60 N
   F_t = 25 N
   F = F_c sin α + F_t cos α
   = 60 sin 15 + 25 cos 15
   = 39.6773 N
   Ratio of frictional energy to total energy
   

   =	F	.	Vc	=	F		t
   	Fc		V		Fc		tc

   
   

   =	39.6773	×	0.010	= 0.4408
   	60		0.015

   Correct Option: A

   t = 0.010 mm
   v = 130 m/min
   α = 15°
   b = 6 mm
   t_c = 0.015 mm
   F_c = 60 N
   F_t = 25 N
   F = F_c sin α + F_t cos α
   = 60 sin 15 + 25 cos 15
   = 39.6773 N
   Ratio of frictional energy to total energy
   

   =	F	.	Vc	=	F		t
   	Fc		V		Fc		tc

   
   

   =	39.6773	×	0.010	= 0.4408
   	60		0.015

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