Say you’re a lawn mowing professional or just your regular average ol homeowner, but you’re extremely careful and never hit rocks or damage the blade in any way. The mower blades still get dull, with only blades of grass and grass is not a hard substance. How does something soft like grass, dull a lawn mower blade?
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In the same way that your beard dulls the blade of a razor.
The tip gets to a very sharp point, which makes it fairly brittle. Eventually it loses that edge and then it would be considered dull
Along with dulling from grass alone, I imagine the blade spinning agitates sand/gravel too (I “leaf blow” trails in my woods with the deck raised and I actually see an occasional spark from this when it’s getting dark).Throw in some acorns and there you have it
I own a professional lawn care business. We cut more lawns in one day than the average homeowner does in one year. Depending on the lawn density we may have to sharpen them more that EVERY week. If the lawns are wet then we will need to sharpen them before the next day.
The blades on our equipment spin at 350ft per second (240mph). Just like your hand smacking water at that speed it hurts. So the blades hitting the thick wet grass at the speed will dull the edge of the blades especially when wet.
Water running over granite in time will erode that stone.
Grass is not entirely made of soft things. A few percent of it is silica that forms into little phytoliths. Silica is harder than steel, so the tiny bits of silica can dull the steel.
Also, when you mow, your mower blades pick up a lot of sand, dirt, sticks, rocks, and other debris as well.
1. Something doesn’t have to be harder than steel to damage the blade over enough repeated impacts. Remember, your hair can dull a razor, and water can wear through solid rock. Given how fast the mower blades spin, you’re racking up millions of grass-blade impacts pretty quickly, and each one is a high-speed smack.
2. Even with very careful use, the blade is getting hit with some things that ARE harder than steel. Sure you’re not hitting big rocks, but “dust” is also rocks, just very small ones. So as you mow, the sharp blade is constantly flying through a cloud of tiny rocks, which make tiny scratches that add up.
Your grass and dirt could be too acidic. You now how tomatoes, because of their acidity dull a knife? Might wanna check the pH in your yard.
To add something to this, if you ever sharpen your own mower blades, don’t try to get an extremely sharp edge on the blade. The sharper they are, the quicker they will get dull. They should be about as sharp as a butter knife and you should be able to touch them without cutting yourself.
Water in and on the grass is dulling the blades.
Water is not compressible. That means that when the spinning blade hits a water droplet, however small, a portion of the water at the impact site becomes as hard as a diamond.
These “micro diamonds” will quickly wear away everything, even diamond tipped blades.
Heard of death by a thousand cuts? That.
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