691. Friction at the tool-chip interface can be reduced by
     

1. 1. decreasing the rake angle
      

   
   
   

   2. increasing the depth of cut
      

   
   
   

   3. decreasing the cutting speed
      

   
   
   

   4. increasing the cutting speed

   
   
   

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1. View Hint View Answer Discuss in Forum

   By increasing the cutting speed, heat dissipation is increased so maximum temperature is decreased. Hence coefficient of friction is decreased.

   Correct Option: D

   By increasing the cutting speed, heat dissipation is increased so maximum temperature is decreased. Hence coefficient of friction is decreased.

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692. During orthogonal cutting of MS with a 10 deg rake angle tool, the chip thickness ratio was obtained as 0.4. The shear angle (in degrees) evaluated from this data is
     

1. 1. 6.53
      

   
   
   

   2. 20.22
      

   
   
   

   3. 22.94
      

   
   
   

   4. 50.00

   
   
   

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1. View Hint View Answer Discuss in Forum

   tanφ =	rcosα
   	1 - rsinα

   
   where, r = 0.4 and α = 10°
   

   ∴ tanφ =	0.4cos10°
   	1 - 0.4sin10°

   
   or φ = 22.94°

   Correct Option: C

   tanφ =	rcosα
   	1 - rsinα

   
   where, r = 0.4 and α = 10°
   

   ∴ tanφ =	0.4cos10°
   	1 - 0.4sin10°

   
   or φ = 22.94°

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693. A built up edge is formed while machining
     

1. 1. ductile material at high speed
      

   
   
   

   2. ductile materials at low speed
      

   
   
   

   3. brittle materials at high speed
      

   
   
   

   4. brittle materials at low speed

   
   
   

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1. View Hint View Answer Discuss in Forum

   BUE is formed while machining ductile materials at low speed.
   

   Correct Option: B

   BUE is formed while machining ductile materials at low speed.
   

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694. What is the approximate% change in the life, f, of the tool with zero rake angle used in orthogonal cutting when its clearance angle, α, is changed from 10 to 7 deg?
     (Hint: Flank wear rate is proportional to cotα)
     

1. 1. 30% increase
      

   
   
   

   2. 30% decrease
      

   
   
   

   3. 70% increase
      

   
   
   

   4. 70% decrease

   
   
   

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1. View Hint View Answer Discuss in Forum

   Wear rate is proportional to tanγ, i.e. Wear rate ∝ tanγ
   Where, γ = Clearance angle
   When clearance angle is decreased from 10° to 7°, then
   

   percentage change in f =	tan10° - tan7°	× 100 = 30.37% decrease.
   	tan10°

   Correct Option: B

   Wear rate is proportional to tanγ, i.e. Wear rate ∝ tanγ
   Where, γ = Clearance angle
   When clearance angle is decreased from 10° to 7°, then
   

   percentage change in f =	tan10° - tan7°	× 100 = 30.37% decrease.
   	tan10°

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695. In orthogonal machining operation, the chip thickness and the uncut chip thickness are equal to 0.45 mm. If the tool rake and is 0 deg. The shear plane angle is
     

1. 1. 45°
      

   
   
   

   2. 30°
      

   
   
   

   3. 18°
      

   
   
   

   4. 60°

   
   
   

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1. View Hint View Answer Discuss in Forum

   r =	Uncut chip thickness	=	0.45	= 1
   	Chip thickness after the metal is cut		0.45

   
   If α = shear plane angle and α = rake angle = 0°
   

   then tanφ =	rcosα	=	1 × cos0	= 1 or φ = 45°
   	1 - rsinα		1 - 1.sin0°

   Correct Option: A

   r =	Uncut chip thickness	=	0.45	= 1
   	Chip thickness after the metal is cut		0.45

   
   If α = shear plane angle and α = rake angle = 0°
   

   then tanφ =	rcosα	=	1 × cos0	= 1 or φ = 45°
   	1 - rsinα		1 - 1.sin0°

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