How sharp should a lawnmower blade be?


Lawnmowers are machines that keep your grass even and your garden beautiful. The lawnmower blades are the key components behind this. Lawnmower blades have a specially developed profile to cut the grass evenly. They spin at high speeds that further enhance the cutting action. In all this, one thing that you may wonder is how sharp the lawnmower blades should be. Generally, they should be sharp enough to cut through rough, tall, and dry grass that comes in their way easily. They should also be able to shear little bushes and twigs too to enhance the garden’s visual appeal. Their sharpness and rotational speed are closely related. A faster speed will need sharper blades so that the cutting is even and causes no damage to blades. This article will entail the lawnmower blade’s sharpness specifications, profile, and cutting-edge parameters.

How sharp should a lawnmower blade be?

To determine blade sharpness, check the blade surface. If the shiny edge is buried underneath dark deposits, the blade has gone blunt and needs sharpening. There shouldn’t be any bends, scratches, and other defects on the cutting edge. A lawnmower blade should not be as sharp as a razor blade. It should have a nice, even profile from one tip to another, and there shouldn’t be any twigs, straws, and grass stuck in between.

Generally, one should sharpen the lawnmower blades once per mowing season, depending on how much you use your mower. Expect it after every 30-40 hours of use. This helps elongate the blade life and protects the mower from other sources of damage too. For a clean and smooth cutting, the blades should be aggressively sharp. If you have no idea about blades’ sharpness and want to sharpen your blades at home, don’t worry. In this article, we will take you through the process of estimating the required sharpness level of your mower’s blades. We will establish a comparison, study the blade profile, and understand the environmental requirement. Stay tuned to this article to have your common queries answered in detail.  

The sharpness of the lawnmower blades will ultimately be the key deciders of their performance. All of the outputs like the smoothness, time efficiency, and evenness of the work ultimately will be decided by the blades’ sharpness. Look into these points to get a better picture of the required sharpness level.

● 1: Inspection of mower blades

At the start of the season, and from time to time throughout the mowing season, do a complete inspection of the lawnmower blades. Look closely for scratches, dents, and bends.  Also, check your lawn to look for signs of a dull blade and lawn damage which can be seen if your green grass seems pale yellow and your mower is leaving patches of grass, i.e., uneven cutting. Each time before you mow your lawn, make sure to clear any sticks, hard rocks, twigs, and thick branches that can damage your lawnmower or the mower’s blade. If the blade is damaged, it should be replaced.

You should examine the blade surface and get an idea of your blades’ condition. In the next steps, we will teach you about the optimum sharpness of blades you must have.

● 2: Sharp blades Vs. Dull lawnmower blades

Mowing your yard with a sharp blade will give a clean and straight cut. A good cut will aid your lawn, and permits the grass to resist any chance of disease. Healthy sharped blades mean healthy grass.  Besides, the mowing is done much more rapidly because the grass gets pretty easy to mow through. This also saves the mower’s engine. If the lawnmower is working hard to cut the grass, it must stress the mower engine.  In this case, your dull blades are affecting the mower engine too.

To identify dull blades, check their surface. If the shiny edge is now buried beneath the dull, dark metal, the blade is dull. The blade edge will be full of nicks and scratches that give off its condition. This kind of blade is harmful to your machine and ineffective for your lawn.

The blades of a mower should be fine; they should be aggressively sharp so that you can see a shiny edge profile easily. However, if you touch the blade by hand, you should only feel the pointy surface, and your hand should not get cut. A sharp blade will be free from scratches, nicks, bends, and defects. Its profile will be discussed next to give you a further idea.

● 3: Blade profile

It is important to sharpen your lawnmower blades each time they get dull without delaying the process too much. This will prevent them from cracking or even breaking up. You do not need an excessively sharp blade but, without doubt, sharper than a butter knife. Lawnmower blades should have a sharp blade profile but not as strong as a razor blade. When you touch the blade while removing or cleaning, you should notice that you can hold the blade without getting a cut.

The few characteristics of a sharp blade’s profile are:

● 4: Type of mowing grass

If you plan to mow a lawn full of weeds, wet grass, and branches, sharpened blades’ definition gets slightly different. In this case, sharpen the blades to an extremely lower angle, around 30 degrees, for better performance. Keep the edges of the blades duller than usual when working on the rough lawn. This is because the twigs and weeds are harder to cut, and also the wetter grass sticks together, making it harder to cut.

Most significantly, with blade edges, the sharpness angle must be 40 degrees but not less than 30 degrees. Anything below that inclination level qualifies as too sharp. The bottom line regarding how sharp a lawnmower blade should be is that it depends on the nature of your yard’s grass and landscape. As a rule of thumb, the level of sharpness (edge leveling and angling) should continue as it was when you bought your lawnmower. It is specified in your operator manual. Whenever buying a lawnmower, always share your yard type with the salesperson as he can better guide you.

Additional concerns:

Keep the sharpening frequency regular, say after every 8th mowing. However, depending on the mower model, blade tempering, and other important factors, you may have to check the blades more often for damage analysis. Most experts guide that homesteaders should sharpen mower blades a maximum of four times a year, and they should replace their blades after a maximum of 5-6 times.

If it proves challenging sharpening and balancing mower blades, refer to a service provider for professional help. It should cost you only a few bucks, usually less than $10, dependent on the blade’s condition.

It would be best if you develop a habit of keeping the sharpness of a mowing blade optimal. Thus, it would help if you always had simple tools like files, a grinder, or a dremel to sharpen the blades.

Frequently asked questions:

1. After how long should I sharpen my blades?

Sharp and efficient blades are crucial for the best mower experience and its extended life. Normally, you should sharpen the blades after every 30-40 hours of use or at least once every season. If you use your machine more often, you will have to sharpen them regularly each month.

2. What are some sharpening techniques used to sharpen the blades?

Some of the sharpening tools you may use to sharpen the mower blades are sharpening stones and rods, angle or bench grinder, or a Dremel. These are fast mechanical tools that accurately develop the blade profile and cutting edge. For a more controlled experience, you may use a flat-file to do the same. 

3. Describe any test to check the sharpness of a lawnmower blade?

You can perform a simple test. It would be best if you had your safety gloves on. Bring a piece of paper while your lawnmower is up on a ramp so that you can access its base easily. Put the piece of paper between the mower’s blades. Try to rotate the mower blades fast with your hands. If the blades are sharp, the paper gets cut sharply. If the blades are dull, the paper will get a poor cut, or it may not get cut at all.

4. Does wet grass dull mower blades faster?

Mowing wet grass will not necessarily dull your mower’s blade faster than dry grass, but it is not good for the lawn and makes it work harder. Wet grass clippings clump together, which require a greater power to cut. This may damage the mower blades too.

Final remarks:

Sharpening the lawnmower blades will help it work more efficiently. Dull blades will put more strain on your lawnmower engine, can cause damage to the grass, leave uncut patches, and use up more fuel. When sharpening the blades, you have to be careful about the sharpness level as too sharp thin blades may break more easily. Depending on the type of grass and your requirements, the sharpness should be set accordingly. The blades should be sharp so that they may not cause an additional load on the engine. This article explains how to determine and set the right level of the blade’s sharpness.

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