Power screws are a common means of translating rotary motion into linear motion. There are several different types, each of which has its own advantages and disadvantages depending on the requirements of the application. Acme lead screws are defined by their thread profile, which is trapezoidal with a thread angle of 29°.
There are two immediate results of this difference in profile. It is much easier to machine, so Acme lead screws are much cheaper than square lead screws or ball screws. The second difference is a much larger area of contact between the screw and the nut. This has both advantages and disadvantages.
First, the load capacity is much higher. Second, there is much higher friction, which makes them much less efficient, but also prevents them from back-driving in most situations. So due to overheating and low efficiency, they are ill-suited for continuous power applications, but are great for vertical motion applications where the load must be suspended without dropping, like lifts and jacks. They are also suitable for medical lab automation and treatment devices, screw press drives, support legs and micro lathes.