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Description
Diagram
Relief Angle One:
Top view - built into the blade
(generally 2-5 degrees)
Relief Angle Two:
End view - To be re-sharpened
(industry average is 30º)
Relief Angle Three:
End view - built into the blade
Top View of Blade Land-side:
Worn Blade Edge
Worn away bottom surface at tip. As shown, is a
sign of poor blade maintenance. The blade will
tear the grass, resulting in a poor looking lawn.
1
2
No Tip = Dull
3
Blade Tip Geometry.
What part of a rotary lawn mower blade cuts the grass?
It is a common misconception that lawn mower blades cut like a knife. It actually has more in common
with the way circular saw teeth cut. The confusion comes from the two shapes; a lawn mower blade
looks like a rectangle, and the circular saw is a circle. Keep in mind that when the
lawn mower blade is in motion it is also a circle. The primary difference is that a circular saw is for wood
or metal. Because these materials are much more dense, more cutting teeth are required. Turf is con
-
siderably less dense than wood or steel so only two teeth are required.
The tips of the blade do the majority of the cutting work; they are the cutting teeth of the blade.
Repeated observation of worn cutting edges show that the first 1-2 inches do the majority of the cutting.
To produce a cutting tip, three relief angles are necessary.
Training Video
Generally 0°
Optimum
