Rack and pinions are used for lifting mechanisms (vertical movement), horizontal motion, positioning mechanisms, stoppers and to permit the synchronous rotation of a number of shafts in general industrial machinery. On the other hand, they are also found in steering systems to change the direction of vehicles. The features of rack and pinion systems in steering are as follows: simple structure, high rigidity, little and lightweight, and excellent responsiveness. With this mechanism, the pinion, installed to the steering shaft, is definitely meshed with a steering rack to transmit rotary motion laterlly (transforming it to linear movement) to ensure that you can control the wheel. In addition, rack and pinions are utilized for many other purposes, such as toys and lateral slide gates.
As a mechanical component to transfer rotary into linear movement, gear racks tend to be in comparison to ball screws. There are pros and cons for using racks instead of ball screws. The advantages of a equipment rack are its mechanical simplicity, huge 
load carrying capacity, no limit to the length, etc. One drawback though may be the backlash. The benefits of a ball screw are the high precision and lower backlash while its shortcomings are the limit in duration due to deflection.
There are applications where the gear rack is stationary, while the pinion traverses and others where in fact the pinion rotates upon a fixed axis while the gear rack moves. The former is used broadly in Spur Gear Rack conveying systems as the latter can be used in extrusion systems and lifting/lowering applications.
To provide many variants of rack and pinion, KHK has various kinds of equipment racks in stock. If the application takes a long duration requiring multiple equipment racks in series, we have racks with the tooth forms properly configured at the ends. These are described as “equipment racks with machined ends”. Whenever a gear rack is created, the tooth cutting procedure and heat treatment process can cause it to try & walk out true. We are able to control this with particular presses & remedial processes.