Friction of a V-thread

Question 1
Marks : +2 | -2
Pass Ratio : 100%
Which of the following screw thread is used for lead screw of lathe?
square thread
trapezoidal threads
buttress threads
V threads
Explanation:
The square threads are employed in screw jacks, presses and clamping devices.
Question 2
Marks : +2 | -2
Pass Ratio : 100%
Which of the following screw thread is used for jacks, vices and clamps?
square thread
trapezoidal threads
buttress threads
acme threads
Explanation:
The square threads are employed in screw jacks, presses and clamping devices.
Question 3
Marks : +2 | -2
Pass Ratio : 100%
A cup is provided in screw jack
to reduce the friction
to prevent rotation of load
to increase load capacity
to increase efficiency
Explanation:
For the prevention of the rotation of load being lift, the load cup of a screw jack is made separate from the head of the spindle.
Question 4
Marks : +2 | -2
Pass Ratio : 100%
The maximum efficiency of square threaded power depends upon
lead angle of screw
friction angle
pitch of screw
nominal diameter of screw
Explanation:
The efficiency of a square threaded screw depends upon the helix angle α and the friction angle φ.
Question 5
Marks : +2 | -2
Pass Ratio : 100%
For self locking screw
φ > α
α > φ
μ < tanα
μ = cosecα
Explanation:
If φ < α, then torque required to lower the load will be negative. In other words, the load will start moving downward without the application of any torque. Such a condition is known as over hauling of screws. If however, φ > α, the torque required to lower the load will be positive, indicating that an effort is applied to lower the load. Such a screw is known as self locking screw.
Question 6
Marks : +2 | -2
Pass Ratio : 100%
For over hauling screw
φ > α
α > φ
φ > α
none of the mentioned
Explanation:
If φ > α, then torque required to lower the load will be negative. In other words, the load will start moving downward without the application of any torque. Such a condition is known as over hauling of screws. If however, φ > α, the torque required to lower the load will be positive, indicating that an effort is applied to lower the load. Such a screw is known as self locking screw.
Question 7
Marks : +2 | -2
Pass Ratio : 100%
Which of the following screw thread is used for transmitting force in one direction?
square thread
trapezoidal threads
buttress threads
v threads
Explanation:
A buttress thread, is used when large forces act along the screw axis in one direction only. This thread combines the higher efficiency of square thread and the ease of cutting and the adaptability to a split nut of acme thread.
Question 8
Marks : +2 | -2
Pass Ratio : 100%
Which of the following screw thread is stronger than other threads?
square thread
trapezoidal threads
buttress threads
V threads
Explanation:
Buttress thread is stronger than other threads because of greater thickness at the base of the thread. The buttress thread has limited use for power transmission. It is employed as the thread for light jack screws and vices.
Question 9
Marks : +2 | -2
Pass Ratio : 100%
The efficiency of square threaded power depends upon
mean diameter of screw
coefficient of friction
pitch of screw
all of the mentioned
Explanation:
None.
Question 10
Marks : +2 | -2
Pass Ratio : 100%
Which of the following screw thread is adaptable to split type nut?
square thread
trapezoidal threads
buttress threads
v threads
Explanation:
An acme or trapezoidal thread, is a modification of square thread. The slight slope given to its sides lowers the efficiency slightly than square thread and it also introduce some bursting pressure on the nut, but increases its area in shear. It is used where a split nut is required and where provision is made to take up wear as in the lead screw of a lathe.