Further to the basics of cutting height (you can read more here) and how it influences the quality of your lawn, let’s examine the equally important quality of cut (QOC).
In a separate blog entry I used the roses in the blender analogy to illustrate what happens to tender grass blades when cut using a rotary lawn mower. The key element at work in mowing grass with a rotary mower is SPEED – speed of the blade turning fast enough to tear or flail the tips off of the grass being mowed.
You may be surprised to learn that only the last ¼ to ½ inch of a rotary lawn mower blade ever does any actual cutting, but if you think about it the blade is moving so fast, that as you push the mower forward only that portion of the blade makes contact with the longer grass blade – everything farther down the blade just passes over the already mowed grass.
The sharpness of the blade is another misunderstood concept. Many people believe that a rotary blade should be extremely sharp, this is a misnomer:
Firstly, if you use a rotary you know that a razor sharp blade is impossible to maintain, just a few minutes of cutting will dull rotary blades significantly. The lifting force that many rotary mowers are designed with today also brings all kinds of debris into contact with the blade, dulling it significantly. That is why a rotary mower dealer or mechanic will not even recommend a blade that sharp, because it can’t be kept that way and is more susceptible to damage as you try to make it sharper and the leading edge becomes thinner.
Finally you would need to sharpen the rotary blade after every mowing, which is not only inconvenient; it can be dangerous if you are not careful and know what you are doing. If the blade is not perfectly balanced each time it can put tremendous strain on the mower as an unbalance blade spins irregularly on the drive shaft of the engine.
The bottom line is that the only way a rotary can mow grass is by shear speed and to smash the tips off the blades of grass. No matter what you do, you cannot overcome this mode of mowing action with a rotary lawn mower.
Great post, with regard to how sharp the blades are , there must be a point where they are sharp enough to cut efficiently but strong enough to keep an edge.