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Which of the following is true for a self-locking screw?
  • a)
    The coefficient of friction is equal to or greater than the tangent of the helix angle.
  • b)
    The coefficient of friction is half of the tangent of the helix angle.
  • c)
    The coefficient of friction is twice the tangent of the helix angle.
  • d)
    The coefficient of friction is less than the tangent of the helix angle.
Correct answer is option 'A'. Can you explain this answer?
Verified Answer
Which of the following is true for a self-locking screw?a)The coeffic...
For a self - locking screw, the coefficient of friction is equal to or greater than the tangent of the helix angle.
In the Power screw, the torque Mt required to lower the load is given by
Mt = Wdm/2 tan (ϕ−α) where, W = load on the screw in N, dm = the mean diameter of the screw-in m,
ϕ = friction angle and α = helix angle
Case 1. when ϕ ≥ α
tan (ϕ - α ) ≥ 0, thus Mt ≥ 0.
i.e., positive torque is required to lower the load. Thus the load will not turn the screw and will not descend on its own unless an effort is applied.
Such cases of screws are known as 'Self-locking screws.’ And the screw will hold the hold without any application of the brake.
Also, as ϕ ≥ α
tan ϕ ≥ tan α
Case 2. when ϕ < />
tan (ϕ - α ) < 0,="" thus="" />t < />
i.e., negative torque is required to lower the load. The load will turn down the screw and will descend on its own unless a restoring torque is required to hold the load.
Such cases of screws are known as 'overhauling of the screw' or back drawing of the screw.
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Most Upvoted Answer
Which of the following is true for a self-locking screw?a)The coeffic...
Explanation:

Self-locking screws are used in applications where vibration may cause the fastener to loosen. These screws have a feature that prevents them from coming loose due to vibrations or other forces. The mechanism that makes a screw self-locking is the difference between the helix angle of the screw and the coefficient of friction between the screw and the mating surface.

Coefficient of Friction:

The coefficient of friction is a value that represents the resistance of one surface to sliding over another. It is calculated by dividing the force required to move one surface over another by the weight of the object. The coefficient of friction is a dimensionless number that ranges from 0 to 1.

Helix Angle:

The helix angle of a screw is the angle between the screw's axis and the line of its threads. It is measured in degrees or radians. The helix angle determines the screw's lead, which is the distance that the screw advances axially in one complete revolution.

Self-Locking Screw:

A self-locking screw is designed to prevent loosening due to vibration or other forces. The screw achieves this by having a greater coefficient of friction than the tangent of the helix angle. This means that the force required to loosen the screw is greater than the force required to move it along its threads.

Conclusion:

In conclusion, option A is the correct answer because the coefficient of friction of a self-locking screw is equal to or greater than the tangent of the helix angle. This ensures that the screw remains in place and does not loosen due to vibrations or other forces.
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Which of the following is true for a self-locking screw?a)The coefficient of friction is equal to or greater than the tangent of the helix angle.b)The coefficient of friction is half of the tangent of the helix angle.c)The coefficient of friction is twice the tangent of the helix angle.d)The coefficient of friction is less than the tangent of the helix angle.Correct answer is option 'A'. Can you explain this answer?
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Which of the following is true for a self-locking screw?a)The coefficient of friction is equal to or greater than the tangent of the helix angle.b)The coefficient of friction is half of the tangent of the helix angle.c)The coefficient of friction is twice the tangent of the helix angle.d)The coefficient of friction is less than the tangent of the helix angle.Correct answer is option 'A'. Can you explain this answer? for SSC 2024 is part of SSC preparation. The Question and answers have been prepared according to the SSC exam syllabus. Information about Which of the following is true for a self-locking screw?a)The coefficient of friction is equal to or greater than the tangent of the helix angle.b)The coefficient of friction is half of the tangent of the helix angle.c)The coefficient of friction is twice the tangent of the helix angle.d)The coefficient of friction is less than the tangent of the helix angle.Correct answer is option 'A'. Can you explain this answer? covers all topics & solutions for SSC 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Which of the following is true for a self-locking screw?a)The coefficient of friction is equal to or greater than the tangent of the helix angle.b)The coefficient of friction is half of the tangent of the helix angle.c)The coefficient of friction is twice the tangent of the helix angle.d)The coefficient of friction is less than the tangent of the helix angle.Correct answer is option 'A'. Can you explain this answer?.
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