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A grader, also commonly referred to as a road grader, motor grader, or simply blade, is a form of heavy equipment with a long blade used to create a flat surface during grading. Although the earliest models were towed behind horses, and later , most modern graders are self-propelled and thus technically "motor graders".
Typical graders have three , with the steering wheels in front, followed by the grading blade or mouldboard, then a cab and engine atop tandem rear axles. Some graders also have front-wheel drives for improved performance. Some graders have optional rear attachments, such as a ripper, scarifier, or compactor. A blade forward of the front axle may also be added. For and some dirt grading operations, a main blade extension can also be mounted.
Capacities range from a blade width of 2.50 to 7.30 m (8 to 24 ft) and engines from 93–373 kW (125–500 horsepower). Certain graders can operate multiple attachments, or be designed for specialized tasks like underground mining.
Graders are commonly used in the construction and maintenance of dirt road and gravel road roads. In constructing paved roads, they prepare a wide flat base course for the final road surface. Graders are also used to set native soil or gravel foundation pads to finish grade before the construction of large buildings. Graders can produce canted surfaces for drainage or safety. They may be used to produce drainage ditches with shallow V-shaped cross-sections on either side of highways.
Steering is performed via a steering wheel, or a joystick capable of controlling both the angle and cant of the front wheels. Many models also allow frame articulation between the front and rear axles, which allows a smaller turning radius in addition to allowing the operator to adjust the articulation angle to aid in the efficiency of moving material. Other implement functions are typically hydraulically powered and can be directly controlled by , or by joystick inputs or electronic switches controlling electrohydraulic servo valves.
Graders are also outfitted with modern digital grade control technologies, such as those manufactured by Topcon, Trimble Navigation, Leica Geosystems, or Mikrofyn. These may combine both laser and GPS guidance to establish precise grade control and (potentially) "stateless" construction. Manufacturers such as John Deere have also begun to integrate these technologies during construction.
The era of motorization by , , truck, and saw such towing graders grow in size and productivity. The first self-propelled grader was made in 1920 by the Russell Grader Manufacturing Company, which called it the Russell Motor Hi-Way Patrol. These early graders were created by adding the grader blade as an attachment to a generalist tractor unit. After purchasing the company in 1928, Caterpillar went on to truly integrate the tractor and grader into one design—at the same time replacing continuous track tracks with wheels to yield the first rubber-tire self-propelled grader, the Caterpillar Auto Patrol, released in 1931.
In some locales such as Northern Europe, Canada, and places in the United States, graders are often used in municipal and residential snow removal. In scrubland and grassland areas of Australia and Africa, graders are often an essential piece of equipment on , large , and to make dirt tracks where the absence of rocks and trees means bulldozers are not required. In New Zealand, both tractor and horse drawn machines were called scoops and they were also used for railway building.
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