311. A grinding ratio of 200 implies that the

1. 1. grinding wheel wears 200 times the volume of the material removed.

   
   
   

   2. grinding wheel wears 0.005 times the volume of the material removed

   
   
   

   3. aspect ratio of abrasive particles used in the grinding wheel is 200

   
   
   

   4. ratio of volume of abrasive particle to that of grinding wheel is 200

   
   
   

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1. View Hint View Answer Discuss in Forum

   Grinding ratio is defined as
   

   =	Volume of work material removed (Vm)
   	Volume of wheel wear (Vw)

   
   

   200 =	Volume of work material removed (Vm)
   	Volume of wheel wear (Vw)

   
   Grinding wheel wears 0.005 times the volume of material removed.

   Correct Option: B

   Grinding ratio is defined as
   

   =	Volume of work material removed (Vm)
   	Volume of wheel wear (Vw)

   
   

   200 =	Volume of work material removed (Vm)
   	Volume of wheel wear (Vw)

   
   Grinding wheel wears 0.005 times the volume of material removed.

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312. Using the Taylor's tool life equation with exponent n = 0.5, if the cutting speed is reduced by 50%, the ratio of new tool life to original tool life is

1. 1. 4

   
   
   

   2. 2

   
   
   

   3. 1

   
   
   

   4. 0.5

   
   
   

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1. View Hint View Answer Discuss in Forum

   V2 =	V1
   	2

   
   V₁T₁^0.5 = V₂T₂^0.5
   

   V1T10.5 =	V1	T20.5
   	2

   
   

   ∴			T2		0.5	= 2
   			T1

   
   

   ∴	T2	= 21/0.5 = 4
   	T1

   Correct Option: A

   V2 =	V1
   	2

   
   V₁T₁^0.5 = V₂T₂^0.5
   

   V1T10.5 =	V1	T20.5
   	2

   
   

   ∴			T2		0.5	= 2
   			T1

   
   

   ∴	T2	= 21/0.5 = 4
   	T1

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313. During the turning of a 20 mm diameter steel bar at a spindle speed of 400 rpm, a tool life of 20 minute is obtained. When the same bar is turned at 200 rpm, the tool life becomes 60 minute. Assume that Taylor's tool life equation is valid. When the bar is turned at 300 rpm, the tool life (in minute) is approximately ____ .

1. 1. 25

   
   
   

   2. 32

   
   
   

   3. 40

   
   
   

   4. 50

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: B

   NA

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314. In an orthogonal machining with a tool of 9° orthogonal rake angle, the uncut chip thickness is 0.2 mm. The chip thickness fluctuates between 0.25 mm and 0.4 mm. The ratio of the maximum shear angle to the minimum shear angle during machining is______.

1. 1. 1.487

   
   
   

   2. 1.499

   
   
   

   3. 1.494

   
   
   

   4. 1.490

   
   
   

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1. View Hint View Answer Discuss in Forum

   Given α = 9°
   t = 0.2 mm
   t _{c max} = 0.4 mm
   t_cmin = 0.25 mm
   
   or Φ_min = 28.18°
   

   Ratio =	Φmax	=	42.09	= 1.494
   	Φmin		28.18

   Correct Option: C

   Given α = 9°
   t = 0.2 mm
   t _{c max} = 0.4 mm
   t_cmin = 0.25 mm
   
   or Φ_min = 28.18°
   

   Ratio =	Φmax	=	42.09	= 1.494
   	Φmin		28.18

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315. A block of length 200 mm is machined by a slab milling cutter 34 mm in diameter. The depth of cut and table feed are set at 2 mm and 18 mm/minute, respectively. Considering the approach and the over travel of the cutter to be same, the minimum estimated machining time per pass is minutes.

1. 1. 14

   
   
   

   2. 13

   
   
   

   3. 12

   
   
   

   4. 23

   
   
   

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1. View Hint View Answer Discuss in Forum

   
   L = 200 + 2x
   x = √17² - 15² = 8
   ∴ L= 216 mm
   

   Time =	L	=	216	= 12 min
   	fN		18

   Correct Option: C

   
   L = 200 + 2x
   x = √17² - 15² = 8
   ∴ L= 216 mm
   

   Time =	L	=	216	= 12 min
   	fN		18

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