Question

The friction torque for square thread at mean radius while raising load is given by (\(\omega\) = load, \(R_o\) = mean radius, \(\phi\) = angle of friction, \(\alpha\) = lead angle):

• A. \( \omega R_o \tan (\phi - \alpha) \)
• B. \( \omega R_o \tan (\phi + \alpha) \)
• C. \( \omega R_o \tan \alpha \)
• D. \( \omega R_o \tan \phi \)

Hint:

In thread design, friction torque is an important factor in determining the efficiency of load transmission. Remember that the lead angle plays a significant role in modifying the frictional force.

Answer 1

The Correct Option is A

The friction torque for square thread at the mean radius while raising the load is given by the formula \( \omega R_0 \tan (\phi - \alpha) \). Here, \( \omega \) represents the load, \( R_0 \) is the mean radius, \( \phi \) is the angle of friction, and \( \alpha \) is the lead angle. The torque depends on the friction between the threads and the angle of the applied load. This formula accounts for the reduction in frictional torque due to the lead angle, which is crucial for understanding the efficiency of threaded systems.