Since costs can add up when purchasing several blades throughout the year, proper mower blade care is also an economical consideration. Damaged and bent blades are inevitable occurrences, so it is important to have extra sets of blades available. "It is a good idea to always have a spare set of blades on hand that can be resharpened when the other set is being used," said John Kuhn, senior engineer, commercial mower development, John Deere, Horicon, Wis.
Blades can become excessively worn through resharpening or sandblasting in sandy areas. Kuhn said certain regions' soil types may wear out a blade's airlift portion more quickly, but be aware that over-sharpening can be detrimental to the blade effectiveness. "I believe if the cutting edge has been sharpened enough to move it back more than ¼ inch to 3/8 inch, it should be replaced," he said, adding that when sharpening the blade contractors should blend the sharpened area into the rest of the blade to avoid creating a notch.
Kuhn cautioned against blades with a notch between the flat portion and the airlift portion, which makes the blade more prone to fatigue breakage. Breakage also can be exacerbated with double blades, or placing two blades on each spindle in a cross-configuration, said Bill Wright, president, Wright Manufacturing, Frederick, Md. "Doubling of the mass creates a far greater time delay on clutch slippage on blade start-up and on the blade brake on blade shut-down, which would reduce both of these components' life expectancy," he said.
| BUYING THE RIGHT BLADE |
When a person looks at buying a blade for his mower, he should understand what it is designed to do. Contractors have many different blades to choose from: notched airfoil, solid airfoil, low airfoil and mulch. All of these blades act differently for different conditions. With the availability of different design and functions, a person can change the type of blades he or she is using to better suit his or her mowing conditions. A notched airfoil is Exmark's standard blade. This blade produces a lot of lift and moves a lot of air. The notched airfoil blade produces maximum discharge velocity and is ideal for heavy, thick, hard-to-lift grasses. With the high lift of the blade and cutting conditions, the blade takes full advantages of a unit's horsepower. Some of the negative effects we see with this blade can be build-up on the underside of the deck (with certain grasses) and blowout in areas where the grass is thin. The solid airfoil is a high-lift blade without the notch in it. This blade produces a strong lift and it is a step down from the amount of air movement that the notched airfoil produces. The solid airfoil will have slightly less discharge velocity, blowout and can help with build-up problems under the deck. This blade works well in drier grass conditions in the summer, fall or in the southern region grasses of the United States. These blades are also used more by state, park, recreational and municipality concerns with rougher mowing conditions. These blades tend to be tougher by design. Low-lift blades are very similar to the solid airfoil blades. The low-lift blades are as the name state - they produce a much lower amount of lift. With low-lift blades you will see substantial reduction in any blowout and less discharge velocity. Low-lift blades are a good choice for thin, dry or stiff grasses. These blades are great for the contractor in sandy areas of the county. They increase the life on the bottom of the deck and the discharge chute. These blades use very little horsepower to run and greatly reduce any grass build-up under the deck. Mulch blades are designed to cut clippings and put them back into the lawn. The Exmark mulching blade has a medium amount of lift airfoil at the tip. They also have an airfoil to force the clippings back into the lawn; this is noted by the wavy design of the blade. This blade works great in all types of grasses and light to medium leaf build-up. Heavy build-up of leaves or overgrown grass will often require double cutting with any mulching application. The operator also needs to take into consideration the season of the year and the moisture content of the grass. Let's say that you have thick bluegrass and it is springtime. This would be where a notched airfoil would be a good choice or a solid airfoil if build-up becomes an issue. If you are cutting centipede or zoysia grasses in the southern regions, or in sandy conditions, a low-lift blade would be a very good choice. The last bit of information everyone should keep in mind is nine times out of 10, slowing down slightly can help more than anything. When mowing at full speeds conditions and consistency change rapidly in the turf. Slowing down may do more for you than any blade you may find. -Paul Jurgens The author is director of customer service, Exmark, Beatrice, Neb. |
When replacing blades, balance the blade carefully, stated Jaret Bishop, president, Custom Lawn Care & Landscaping, Washington Court House, Ohio. Unbalanced blades cause vibration of the entire system, resulting in the wear of other components.
Paul Jurgens, director of customer service, Exmark, Beatrice, Neb., offered some additional pointers for replacing mower blades. "After you have removed the blade from the unit that needs to be sharpened, carefully inspect the air foil of the blade to make sure that sand or dirt has not undercut the airfoil," he said. "If the airfoil were to break free during mowing, it could do considerable damage to whatever it hits.
"You also need to be careful when installing a sharpened blade to make sure it is secured properly while tightening the blade bolt," he continued. "There have been lots of nasty cuts inflicted by a non-moving mower blade."
Kuhn added that blades must be fed properly onto the spindle so they are centered. Some spindles offer pilot mechanisms that guide the blade into place, he added. Further, he stressed that contractors should always wear gloves when handling blades.
The author is assistant editor of Lawn & Landscape magazine.
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