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23 FEBRUARY 2019
If you need to finish or maintain an unpaved road or dig or clean a ditch, motor graders are indispensable machines. These heavy-duty six-wheelers can tackle the hardest road surfaces, but they require a skilled operator to ensure even results and prevent problems such as potholes and washboarding from recurring. Choosing a motor grader 

Motor graders are fitted with a range of blade sizes suited to different tasks. 10ft and 12ft graders are ideal for smaller tasks such as preparing car parks and subdivisions, while road finishing and maintenance will generally require a 14ft blade.

The operator should familiarise themselves with the different blade movements so they can switch between these when needed. Cutting requires a tighter blade, while mixing and spreading materials require the blade to be looser.

Blade angle

Keep the cutting edge of the motor grader blade at 90 degrees to the road surface, unless you're creating a slope. This puts less stress on the blade and lowers the risk of damage from objects on the road. Avoid using excess pressure, as this increases wear on the cutting edge as well as consuming more fuel.

Mouldboard angle

Unlike the blade, the mouldboard can be angled between 10 and 50 degrees depending on the depth of cut needed. Angles of 10–30 degrees are suitable for light and loose material, while hard and sticky materials, ditches and finishing usually require steeper angles of 30–50 degrees.

The top of the mouldboard should be about 5cm in front of the cutting edge to start off, but this should be adjusted according to materials and conditions.

Dressing the road 

Road surfaces should be moist before dressing. Recent rainfall could be enough for a smaller surface area, but a larger project will require a water truck. Check for good drainage to prevent washboarding and potholes.

Straight and curved roads

Straight roads should have a narrow 3 percent slope from the shoulder to the centre. Curved roads should be completely flat, with a 6 percent incline on the inside of corners. Trim the cutting edge of the blade periodically to keep it straight.


Filling potholes with loose material is ineffective, as this won't stand up to traffic and will likely need maintenance again in the near future. Instead, the surrounding road surface should be cut to the depth of the largest pothole.


Roadside ditches should be around 5cm lower than the road wear surface, though this depends on the road material and soil type. Areas with high rainfall should have deeper ditches or an elevated road surface to prevent flooding or water running beneath the road and causing potholes.


Make sure the blade is at 90 degrees from the road surface and the mouldboard tipped further forwards for finishing work, though this can vary depending on road conditions.

Motor graders hire

If you need motor grader, skid steer or excavator hire for road maintenance, ditch building or other projects, Coates Hire has 10ft, 12ft and 14ft graders for hire Australia wide. See our motor graders range.


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