66. Modern gear tooth profile is given involute shape because

1. 1. this is a very easy curve for manufacturing

   
   
   

   2. sliding does not takes place anywhere on meshing teeth

   
   
   

   3. involute is the only profile that gives conjugate action

   
   
   

   4. change in the centre distance does not change gear ratio

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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67. For full depth of involute spur gears, minimum number of teeth of pinion to avoid interference depends upon

1. 1. pressure angle

   
   
   

   2. speed ratio

   
   
   

   3. circular pitch

   
   
   

   4. pitch diameter

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: A

   NA

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68. For full depth of involute spur gears, minimum number of teeth of pinion to avoid interference depends upon

1. 1. pressure angle

   
   
   

   2. speed ratio

   
   
   

   3. circular pitch

   
   
   

   4. pitch diameter

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: A

   NA

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69. The basic load rating of a ball bearing is

1. 1. the maximum static radial load that can be applied without causing any plastic deformation of bearing components

   
   
   

   2. the radial load at which 90% of the group of apparently identical bearings run for on million revolutions before the first evidence of failure

   
   
   

   3. the maximum radial load that can be applied during operation without any plastic deformation of bearing components

   
   
   

   4. a combination of radial and axial loads that can be applied without any plastic deformation

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: B

   NA

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70. The dynamic load capacity of 6306 bearing is 22 kN. The maximum radial load it can sustain to operate at 600 rev/min, for 2000 hours is

1. 1. 4.16 kN

   
   
   

   2. 3.60 kN

   
   
   

   3. 6.25 kN

   
   
   

   4. 5.29 kN

   
   
   

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1. View Hint View Answer Discuss in Forum

   Number of revolutions in life = 2000 × 60 × 600
   = 72 × 10⁵ revolutions
   ∴  L = 72
   

   Maximum radial load =	2 2	=	2 2
   	³√L		³√7 2

   
   = 5.29 kN

   Correct Option: D

   Number of revolutions in life = 2000 × 60 × 600
   = 72 × 10⁵ revolutions
   ∴  L = 72
   

   Maximum radial load =	2 2	=	2 2
   	³√L		³√7 2

   
   = 5.29 kN

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