Abrasive Hardness vs Strength: Key Differences & How to Choose
To clarify, consider these three key differences:
1. Physical scope: Hardness is a "surface" property, while strength is an "overall" (bulk) property.
2. Behavioral characteristics: High hardness is like a glass cutter (it can score glass, but might shatter if dropped); high strength is like a rubber ball (it cannot scratch glass, but won't break when dropped).
3. Practical impact: Insufficient hardness causes grains to slip without cutting; insufficient strength leads to premature fracturing and waste; excessive strength means that even when grains become dull, they fail to break away, which can cause the workpiece to overheat or burn (this is where "self-sharpening" is needed to maintain balance).
The two must work in tandem:
An effective abrasive requires high hardness for cutting, balanced with an appropriate level of strength to ensure self-sharpening. For example, brown fused alumina has moderate strength—it can fracture locally once it becomes dull, making it well-suited for grinding standard steel. Conversely, while diamond possesses the highest hardness, its strength is relatively low (it is brittle); it may shatter under intense impact, making it unsuitable for heavy-duty rough grinding.
In short, when selecting an abrasive, the goal is to find the right balance between hardness and strength. Hard materials (such as cemented carbides) require extremely high hardness, though strength can be somewhat lower; heavy-duty rough grinding (such as deburring), by contrast, requires high strength and moderate hardness.