Trapezoidal threads are better than square threads as there is radial pressure or side thrust on the nut.

Power Screws topics include: Concepts of power screws, self locking screws and screw efficiency. A power screw, also known as a lead screw, is a mechanical device that converts rotary motion into linear motion. They can be used to lift or move large loads, and are capable of a large mechanical advantage.  Power screws are used to transfer power, as opposed to threaded fasteners, which are used to clamp the machine members.  They have many advantages, including: Large load carrying capability Simple to design Easy to manufacture Large mechanical advantage Precise and accurate linear... Show more

Power Screws topics include: Concepts of power screws, self locking screws and screw efficiency.

A power screw, also known as a lead screw, is a mechanical device that converts rotary motion into linear motion. They can be used to lift or move large loads, and are capable of a large mechanical advantage. 

Power screws are used to transfer power, as opposed to threaded fasteners, which are used to clamp the machine members. 
They have many advantages, including:
Large load carrying capability
Simple to design
Easy to manufacture
Large mechanical advantage
Precise and accurate linear motion
Smooth, quiet, and low maintenance
Most are self-locking 

Power screws are used in many applications, including screw-type jacks, tensile, and compression.

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