Rack and pinions are used for lifting mechanisms (vertical movement), horizontal movement, positioning mechanisms, stoppers and also to let the synchronous rotation of many shafts in general industrial machinery. On the other hand, they are also used in steering systems to change the direction of cars. The features of rack and Spur Gear Rack pinion systems in steering are as follows: simple framework, high rigidity, small and lightweight, and exceptional responsiveness. With this mechanism, the pinion, mounted to the steering shaft, is usually meshed with a steering rack to transmit rotary motion laterlly (transforming it to linear motion) to ensure that you can control the wheel. In addition, rack and pinions are used for various other purposes, such as playthings and lateral slide gates.
As a mechanical element to transfer rotary into linear movement, gear racks tend to be in comparison to ball screws. There are advantages 
and disadvantages for using racks instead of ball screws. The advantages of a equipment rack are its mechanical simplicity, huge load carrying capacity, and no limit to the space, 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 are 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 the pinion rotates on a fixed axis while 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 takes 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 “equipment racks with machined ends”. When a equipment rack is created, the tooth cutting process and heat treatment process could cause it to try & walk out true. We can control this with unique presses & remedial processes.