36. A metal disc of 20 mm diameter is to be punched from a sheet of 2 mm thickness. The punch and the dia clearance is 3%. The required punch diameter is
    

1. 1. 19.88 mm
      

   
   
   

   2. 19.94 mm
      

   
   
   

   3. 20.06 mm
      

   
   
   

   4. 20.12 mm

   
   
   

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1. View Hint View Answer Discuss in Forum

   Punch diameter = 20 – 2 × 3% of thickness
   

   Punch diameter = 20 – 2 ×	3	× 2 = 20 - 0.12 = 19.88 mm
   	100

   
   

   Thickness of blank =	1.5	= 3 mm
   	cos60°

   Correct Option: A

   Punch diameter = 20 – 2 × 3% of thickness
   

   Punch diameter = 20 – 2 ×	3	× 2 = 20 - 0.12 = 19.88 mm
   	100

   
   

   Thickness of blank =	1.5	= 3 mm
   	cos60°

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37. In blanking operation the clearance is provided on
    

1. 1. The die
      

   
   
   

   2. The punch
      

   
   
   

   3. Both die and punch equally
      

   
   
   

   4. Neither the punch nor the die

   
   
   

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1. View Hint View Answer Discuss in Forum

   Blanking operation cleanness is provided on. Punch Die will be exact.

   Correct Option: B

   Blanking operation cleanness is provided on. Punch Die will be exact.

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38. The cutting force in punching and blanking operations mainly depends on
    

1. 1. The modulus of elasticity of the material
      

   
   
   

   2. The shear strength of the material
      

   
   
   

   3. The bulk modulus of the material
      

   
   
   

   4. The yield strength of the material

   
   
   

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1. View Hint View Answer Discuss in Forum

   Cutting force = τ × A
   τ = Shear strength
   

   Correct Option: B

   Cutting force = τ × A
   τ = Shear strength
   

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39. A 50 mm diameter disc is to be punched out from a carbon steel sheet 1.0 mm thick. The diameter of the die should be (Take clearance as 3% of sheet thickness) _______.
    

1. 1. 49.925 mm
      

   
   
   

   2. 50.00 mm
      

   
   
   

   3. 50.075 mm
      

   
   
   

   4. None of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   Clearness should be given on punch in Blanking operation. Die should be exact.

   Correct Option: B

   Clearness should be given on punch in Blanking operation. Die should be exact.

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40. The thickness of the blank needed to produce, by power spinning a missile cone of thickness 1.5 mm and half cone angle 30°
    

1. 1. 3.0 mm
      

   
   
   

   2. 2.5 mm
      

   
   
   

   3. 2.0 mm
      

   
   
   

   4. 1.5 mm

   
   
   

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1. View Hint View Answer Discuss in Forum

   Thickness of blank =	cone thickness
   	cos( 2α )

   
   

   Thickness of blank =	1.5	= 3 mm
   	cos60°

   Correct Option: A

   Thickness of blank =	cone thickness
   	cos( 2α )

   
   

   Thickness of blank =	1.5	= 3 mm
   	cos60°

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