Whether motor graders are used as a first step in the rough grading process, for fine grading to prepare dirt for placement of stone, or to grade stone prior to construction of an asphalt base, the equipment must be maintained so it's responsive to the commands of the operator.
On most motor graders a moldboard or blade is attached to a turntable, which is connected to the frame. Hydraulic cylinders lift the turntable (and the blade) up and down while a third cylinder enables the turntable and blade to move from side to side. A system of gears enables the operator to rotate the blade up to 360 degrees if needed.
"The whole machine is there just to push that blade," says Keith Lee, research and development for LeeBoy, which manufacturers four graders in different size categories and recently introduced the 705, a 17,000-lb. machine. "All it's doing is pushing that blade so you need to do everything you can to make it as easy as possible for the machine to do that. When the operator is doing precise work the motor grader needs to be able to respond properly, so certain areas need to be monitored."
The moldboard is where all the action takes place, and that's why special attention needs to be paid to it. This is the part of the machine that engages the soil, cutting it to the proper shape and fine-tuning soil or stone before paving.
"The most important maintenance part of a motor grader is maintaining a good cutting edge on the equipment," says Shannon Chastain, president of Basic Equipment, manufacturer of the Basic Model 601 articulating grader. "All too often the biggest neglect is the cutting edges."
Bolted in place to the moldboard, there is a cutting edge along the bottom of the blade, and some graders also have cutting edges bolted to each side of the blade. Because these edges cut into the dirt and are constantly engaged with the material, they wear out depending on hours of use, abrasiveness of material, and even operator skill.
"Cutting edges and end bits are wear points that need to be monitored and replaced pretty often, occasionally in a single day if you've done a lot of work in an abrasive environment," Lee says.
"Wear also depends on what pitch the operator runs the blade at," Chastain says. "If you're running the blade at a right angle it will wear more slowly, but when the blade is pitched back it will wear on the moldboard more quickly."
Miller Griffith, sales and marketing manager for The Factory Co., manufacturer of the H-Mach Cross Blade utility grader, says a certain depth of the cutting edge needs to be exposed for the grader to work effectively. He says 1½ in. of useable space on the cutting edge will perform fine. "But if you burn through 1 inch of that and you don't replace it you're going to continue to wear it down and eventually wear into the moldboard," Griffith says.
Manufacturers agree that a worst-case scenario involves neglecting the cutting edge of the blade to the point where the work is wearing into the moldboard. "When that happens you lose the integrity of the moldboard to maintain the cutting edge," Chastain says. "You get to the point where you can't replace the cutting edge, so you've got to replace the moldboard."
Some graders, such as the Basic Model 601, use a reversible cutting edge so that when it's worn on one side contractors can unbolt it and flip it around. Cutting edges are held in place by up to a dozen bolts, which cost $3 to $4 each, and should also be replaced because they also operate in the dirt and become worn. Replacement of cutting edges and bolts will cost roughly $100 and take 30 minutes using an air-impact wrench. Manufacturers recommend visually inspecting the cutting edges every 25 to 50 hours depending on the type of material the machine is working in.
Blade slide & turntable
An important component of the moldboard is the blade slide, sometimes called the moldboard slide, which enables the moldboard to move from side to side on a swivel track. The slide relies on guides to control the movement of the slide and the guides will wear down through use.