A ball screw is considered to be a screw, but it is somewhat different from a normal screw. These types of screws are used extensively in commercial and industrial applications. Screws are primarily used to transfer rotational force into linear force and also act as a fastener to hold two objects together. Ball screws are designed to convert rotary motion to linear motion, or torque to thrust, and vice versa. These objects are mainly power screws with a train of ball bearings riding between the screw and the nut in a re-circulating track. The ball screw has a rounded shape to conform to the balls. Ball screws have a predictable service life and a low wear rate.
A regular type of screw consists of a shaft with a helical groove or a thread formed in its surface. The main uses of a screw are as a threaded fastener used to hold objects together, and as a simple machine used to translate torque into linear force. A screw can also be defined as an inclined plane wrapped around a shaft. Screws come in a variety of shapes and sizes and are used for fastening all sorts of objects such as wood and steel.
A typical ball screw would consist of: a screw with a precision shaped helical groove, a nut with an external groove and a set of miniature, precise, steel balls that circulate in the groove between the screw and the nut. The underlying principle being, that as the screw turns, the other component moves in a linear direction. Some examples of ball screws are: large rolled screws, miniature screws and rotating nut systems.
Ball screws are manufactured in various ways such as rolled, milled, or ground. Rolled screws are cold rolled from a blank. Milled screws are created on a milling machine which uses a cutter with an Acme form. Ground screws are manufactured on a grinding wheel, also with an Acme form.
There are some important factors to consider while searching for ball screws and these include the design arrangement, the length of the screw, the outer diameter of the screw, the screw lead, the screw lead accuracy, the dynamic load rating, and the maximum static load capacity of the screw.
The advantage of using a ball screw over a regular type of screw is that it can be removed and used again without reducing its usefulness. Ball screws are made of various materials. The most common among them being steel, but titanium and bronze are also used.