Rack and pinions are used for lifting mechanisms (vertical movement), horizontal motion, positioning mechanisms, stoppers and also to permit the synchronous rotation of a number of shafts in general 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 the following: simple structure, high rigidity, small and lightweight, and exceptional responsiveness. With this mechanism, 
the pinion, installed to the steering shaft, is definitely meshed with a steering rack to transmit rotary Spur Gear Rack movement laterlly (switching it to linear motion) 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 compared to ball screws. There are benefits and drawbacks for using racks instead of ball screws. The advantages of a equipment rack are its mechanical simplicity, large load carrying capacity, no limit to the distance, etc. One disadvantage though may be the backlash. The benefits of a ball screw will be the high precision and lower backlash while its shortcomings include the limit in length due to deflection.
There are applications where in fact the gear rack is stationary, while the pinion traverses and others where in fact the pinion rotates on a fixed axis as the gear rack moves. The previous is used widely in conveying systems as the latter can be used in extrusion systems and lifting/lowering applications.
To provide many variations of rack and pinion, KHK has various kinds of equipment racks in share. If the application requires a long length 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 produced, the tooth cutting process and the heat treatment process could cause it to try & go out of true. We are able to control this with special presses & remedial processes.