What Are Grader Blades and Overlays, and How Do They Work Together?

What Are Grader Blades and Overlays, and How Do They Work Together?

Grader blades (or “moldboard blades”) are the primary working component of a motor grader. They’re large, curved steel plates attached to the front of the grader, designed to scrape, level, and shape terrain. Overlays—thin, wear-resistant steel plates—are welded or bolted to the bottom of the grader blade to protect it from abrasion. Together, they form a durable system that keeps graders working efficiently.

Grader Blades: Their curved shape helps “roll” material forward, making it easier to level. They’re available in different sizes (10–24 feet long) and shapes (flat, curved, serrated) to suit different jobs. For example, a curved blade is great for moving loose material, while a flat blade is better for precise grading.

Overlays: These are the “wear layer” of the blade. They’re made from high-carbon steel or boron steel and are designed to be replaceable. When the overlay wears out, you can remove it and weld a new one—no need to replace the entire blade. This saves money and reduces downtime.

How They Work Together: The grader blade provides the structure and shape needed to move material, while the overlay absorbs the brunt of wear from the ground. For example, when grading a gravel road, the overlay scrapes against the gravel, preventing the blade from wearing out. When the overlay is worn, you simply replace it, and the blade is as good as new.

Overlays are available in different thicknesses (1/4–1/2 inch) and styles (smooth, serrated). Serrated overlays are great for cutting through hard material (like asphalt), while smooth overlays are better for general grading.

In short, grader blades and overlays are a team—one provides the shape, the other provides the wear resistance. Together, they keep graders working for years.