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Lawn Mowing Blade Sharpening

Apr 25 2013

Most people are not aware that there are many styles and shapes of lawn mower blades as there are brand names of the mowers. Some mowing decks will have only one blade, but there are also many that have two and three blades under the deck. The common things here is that they all need to be sharp in order for them to do a good job at making your lawn look great. A blade is sharp not when it has a razor edge, but when it is ground or filed to about the sharpness of  a butter knife. Although it is preferable to have no nicks along the cutting edge, Some sharpeners, will only remove enough to maintain a good cutting edge. Only the first 1.5 to 2.5 inches of the blade are actually cutting, therefore this is the most critical area on the blade. However even in this area it is not necessary to remove all the nicks and dings. The blade will perform very well if the nicks are slowly removed over several sharpenings, and the need to replace them is also extended when they are sharpened out instead of ground out.

The most common blade used today is the mulching blade. It is installed on most new mowers even of they are not  set up for that purpose. These blades have a bend on the cutting side of the blade and are ground to follow this curve. They also will have a small wing bent up along the back edge of the blade. As the mower passes over the lawn a updraft is created lifting the tops of the grass blades allowing the sharpened edge to shear off the top portion of the grass blade. It then passes over the wing and up towards the mowers deck. As it falls back down the mower blade will slice is into finer pieces, allowing it to blend into the lawn better as well as help it decompose faster, thus adding a mulching material to the lawn. On blades of this nature the ground or sharp edge needs to be sharpened evenly even at the two bends of curves along the length. This will ensure a more even cut giving the lawn a more manicured look.

Another blade is one that is flat from one end to the other. While these are not as common any more they are still a good blade when sharpened properly. These rely on a little updraft under the deck, but are a little weak when it comes to pulling up matted grass. Many times these are used on tractor decks that have more than one blade. With several blades turning under the deck more updraft is provided and the results are a nice even cut on the lawn. Many times these are used when the lawn mower is equipped with a bagging system. The clippings are longer in nature, but if they are being bagged they are not left in clumps in the lawn. Again the edge must maintain a proper angle and an even grind along the cutting edge.

There is also the blades that are flat on the cutting side and have a wing to lift the clippings off the back of the blade. These are generally used when the grass in discharged either out the side or back of the mower for distribution into the lawn.

Each one of the above blades will do a good job on the lawn when they are maintained. There is no need to change from one to the other to accomplish a different cutting style. The mulching blade for instance will work just as well for mulching as it does for use as a discharge system. The flat blade can also be used for mulching but will not cut the clipping very fine. Some mower manufacturers supply only one style of blade for the mower. It is always best to keep the same style blade on the mower as the one the manufacturer recommends or supplies.

Below is a different type of blade all together. It is supplied on only select equipment and as you will see sort of combines all the features of all the blades above. Notice there are 4 cutting edges. As with all lawn mower blades when they are sharpened, they must also be balanced. This means that the same amount of material must be removed from one side to the other. With the blade below, it would be best to have a professional sharpen it just to ensure proper balance. A blade that is not balanced will cause the mower to vibrate and can cause damage to the shaft.

Cutting edges are facing the bottom of the picture.

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