Rack and pinions are used for lifting mechanisms (vertical movement), horizontal motion, positioning mechanisms, stoppers and also to let the synchronous rotation of a number of shafts in general industrial machinery. However, they are also found 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, little and lightweight, and superb responsiveness. With this mechanism, the pinion, mounted to the steering shaft, is meshed with a steering rack to transmit rotary motion laterlly (converting it to linear movement) to ensure that you can control the wheel. Furthermore, rack and pinions are used for many other purposes, such as playthings 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 pros and cons for using racks instead of ball screws. The benefits 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 will be the high precision and lower backlash while its shortcomings are the limit in duration due to deflection.
There are Spur Gear Rack applications where in fact the gear rack is stationary, while the pinion traverses and others where the pinion rotates on a fixed axis while the gear rack moves. The former is used broadly in conveying systems as the latter can be utilized in extrusion systems and lifting/lowering applications.
To provide many variants of rack and pinion, KHK has various kinds of equipment racks in share. If the application takes a long duration requiring multiple gear racks in 
series, we have racks with the tooth forms properly configured at the ends. These are described as “gear racks with machined ends”. When a equipment rack is created, the tooth cutting procedure and heat treatment process can cause it to try & go out of true. We can control this with particular presses & remedial processes.
