Rack and pinions are used for lifting mechanisms (vertical movement), horizontal movement, positioning mechanisms, stoppers and to permit the synchronous rotation of a number of shafts generally industrial machinery. On the other hand, also, they are used in steering systems to change the direction of vehicles. The characteristics of rack and pinion systems 
in steering are as follows: simple framework, high rigidity, small and lightweight, and superb responsiveness. With this system, the pinion, Spur Gear Rack installed to the steering shaft, is usually meshed with a steering rack to transmit rotary movement laterlly (transforming it to linear motion) to ensure that you can control the wheel. In addition, rack and pinions are used for several other purposes, such as toys and lateral slide gates.
As a mechanical component to transfer rotary into linear movement, gear racks tend to be compared to ball screws. There are advantages and disadvantages for using racks in place of ball screws. The advantages of a gear rack are its mechanical simplicity, huge load carrying capacity, and no limit to the length, etc. One drawback though is the backlash. The advantages of a ball screw will be 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, as the pinion traverses and others where in fact the pinion rotates on a fixed axis as the gear rack moves. The former is used widely in 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 many types of gear racks in share. If the application takes a long duration requiring multiple equipment racks in series, we have racks with the tooth forms correctly configured at the ends. They are described as “gear racks with machined ends”. Whenever a gear rack is created, the tooth cutting procedure and the heat treatment process could cause it to try & walk out true. We are able to control this with special presses & remedial processes.