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Stump Grinder Product Insight:
Tungsten Carbide-Tipped Teeth

... From computer to tungsten carbide: the computer rendered blue is the tungsten carbide tip of a DR Stump Grinder tooth.

Grinding a stump is heavy duty work and it demands a material that is significantly harder than the stump. You probably remember Mohs Scale from somewhere back in your schooldays. You're less likely to be familiar with the Janka scale which rates the hardness of woods. Now, it’s a safe bet that you don’t have a stump of Australian Buloke on your property, but you may be able to find how the ones you do have measure up in the chart below.

... Wood hardness is ranked on the Janka Scale, measured in Pounds Force (lbf).

Hardness isn’t the whole story though. The Janka scale reflects the amount of force required to sink a steel ball into the surface of the wood. But wood is also fibrous, and the nature of the fiber can play a role in determining how hard the wood is to grind. As can the amount of moisture in the stump. Nevertheless...

No matter how hard or fibrous or waterlogged your stump is, it won’t concern your DR Stump Grinder. Because the DR’s tungsten carbide-tipped teeth are really hard—a different-order-of-magnitude hard. In fact, tungsten carbide is the material of choice for mining equipment that blasts through bedrock. It rates a 9 on Mohs Scale (10 = diamond), and even the very hardest woods would only rate “5ish” on the Mohs scale (an exact calculation isn’t possible because Mohs is merely a relative scale and not an actual measurement).

But as hard as tungsten carbide is, any material used for abrading a softer material will dullen over time, even with its hardness advantage. The DR Stump Grinder’s teeth (there are 8 of them mounted on the cutting head) are designed to anticipate the dulling effect with a cleverly engineered feature that allows you to rotate each tooth to produce a fresh grinding edge.

... Three flat surfaces on each tooth’s collar seat it firmly in the cutting head and can be rotated to bring a fresh grinding surface into play.

When the grinding surface gets dulled in one position, you simply rotate the tooth to the next position (takes just 30 seconds per tooth), and you’ve got a new sharp edge to work with. When all 3 edges are worn, replacing the whole tooth is quick and easy.

... Rotating the teeth to a fresh, sharp edge is quick and easy.

Eventually—many stumps in your future—you may need to replace the teeth entirely. Meanwhile, you can grind with confidence knowing that the material advantage is on your side, and that the stump in front of you will soon be sawdust!