Now this topic going to tell about power screws which one of important topic in machine design, and also important in competitive examinations like gate, ies, other competitive examination, after read this topic you will be seen few important objective type question relevant to this topics which are already came into previous competitive examination, these are leads you success in your examination where if you find this questions in various exams. Generally ,The power screws are used to convert rotary motion into translation motion. Following are the three types of screw threads mostly used for power screws.
- Square thread : It is adapted for transmission of power in either direction . This thread results in maximum efficiency and minimum radial on the nut .The square threads are employed in screw jocks, press, and clamping devices
- Acme or trapezoidal thread : It is a modification of square thread The slight slope given to sides lowers the efficiency slightly then square thread and it also introduce some bursting pressure on nut , but increase its area in shear.
- Buttress thread : It is used when large forces act along the screw axis in one direction only. It has limited use for power transmission .
Note :
- The efficiency of a screw threaded screw is maximum , if the helix angle is equal to (45 deg - angle of friction / 2 )
- The maximum efficiency of a square threaded screw is written by
- A screw is said to be overhauling screw , if the friction angle is less then helix angle . The efficiency of overhauling screws is more then 50%.
- A screw is said to be self locking screw , if the friction angle is more then helix angle . The efficiency of self locking screw is less then 50%.
What is maximum efficiency of square threaded screw ?
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Reviewed by Admin
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10:21:00
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