Castle nut is locking device

Q.  Which among the following statements is/are true?

1. Fracture of bolts occurs due to uneven distribution of impact energy
2. Castle nut is a locking device
3. Fine threads are stronger than coarse threads
4. Coarse threads apply more resistance when loosened

- Published on 14 Sep 15

a. Statement 2 and Statement 3
b. Statement 1 and Statement 2
c. Statement 3 and Statement 4
d. All of the above

ANSWER: Statement 1 and Statement 2
 

    Discussion

  • Sravanthi   -Posted on 04 Nov 15
    - Castle nut is a locking device. These locking devices are provided to avoid dangerous situations as thread fasteners are subjected to vibrations.

    - Castle nut is provided with slots in the cylindrical collar on the hexagonal nut.

    - Fracture of bolts occurs due to uneven distribution of impact energy because the threaded portion absorbs large amount of energy and small amount of energy is absorbed by the shank. The impact energy absorbed per unit volume is directly proportional to square of stress.

    Coarse threads:

    - Coarse threads are stronger than fine threads. These threads offer less resistance and have less possibility of thread shearing and crushing.
    - Coarse threads apply less resistance during loosening or unscrewing. So these threads can be used where frequent assembly or disassembly of connecting parts is needed.
    - These threads are designated as 'M' which is followed by nominal diameter. For eg: M30

    Fine threads:

    - Fine threaded bolts are more stronger than coarse threaded bolts of same hardness because these bolts have large diameter and tensile stress area.
    - The screw body is stronger even though threads weaker.
    - These threads offer more resistance while unscrewing.
    - These threads are designated as 'M' which is followed by pitch and nominal diameter.

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