| Technician |
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Inspecting and Sharpening
Rotary Mower Blades
Figure 2Rotary mowers cut grass by the blade’s cutting surface impacting against the grass
stems at a high velocity. To ensure good quality of cut, the cutting edge of the blade must be kept in a sharp condition. A dull blade will produce a ragged cut
1.Check the blades to ensure that it is not bent and has the correct attitude in rela- tion to the housing and ground surface.
2.The blade must be sharpened correctly.3.Check blade balance each time the blade is sharpened.
DO NOT grind bottom of cutting edge. This will cause poor quality of cut and demand higher horsepower.
Grind top side of cutting edge only. Ideal angle for cutting edge is 30ë.
Figure 1
FLAT PART | SAIL |
OF BLADE |
|
SAIL
WEAR
SAIL
SLOT
FORMED
INCORRECT This will cause poor quality of cut and high horsepower requirement.
CORRECT
INCORRECT Bent lades will cause poor quality of cut and demand higher horsepower.
CORRECT
and will require an excessive amount of engine horsepower to rotate the blade through the grass. The most common causes for rotary mowers not giving a good quality of cut are due to dull cut- ting edges and/or bent blades. Whenever a blade is removed for sharpening:
4.When installing the blade, tighten the blade retaining bolt or nut to the correct torque so it will not loosen during operation.
If blade is allowed to wear, a slot will form between the sail and flat part of the blade (see figure 1).
Eventually a piece of the sail may break off and be thrown from under the housing, possibly resulting in serious injury to yourself or a bystander.
Sharpening Process
Before sharpening the blade, check to make sure it is straight. Lay the blade on a flat surface to check.
Do not try to straighten a blade that is bent, and never weld a broken or cracked blade. Always use a new Toro blade to ensure continued safety certification of the product.
When sharpening the blade, grind the top surface only, trying to maintain the angle of the original cutting edge. Do not grind the bottom surface or a chisel shape will result (see figure 2). The low- est portion on the blade that contacts the grass must be the cutting edge or the grass will not be cleanly cut and excessive horsepower will be required.
To prevent possible personal injury, wear a face shield or safety glasses when grinding or sharpening is being done. After the blade has been sharpened, check the balance. This can best be done
by using a blade balancer tool. A bal-
anced blade will stay in a horizontal posi- tion on the balancer. A blade that is not balanced will settle to the heavy side. If the blade is not balanced, grind some metal off the heavy end of the blade.
Blade Bolt Torque
When installing blades, be sure to tighten the blade retaining bolt to the proper torque. Do not use an air or elec- tric wrench to apply the final torque. To prevent loosening or damaged threads, always use a standard torque wrench to apply the final torque (see figure 3).
Figure 3
Check blade retaining bolt torque any time a blade has hit a solid object. 
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