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Do Lawnmower Blades Come Sharpened?

A properly sharpened lawnmower blade determines how neatly it will cut the grass and believe it or not a dull lawnmower blade can damage the grass of your lawn. Therefore, it is important to keep an eye on your lawnmower blades’ sharpness to keep your lawn healthy and beautiful. But what about the brand new lawnmower blades that you just bought from a store? Do you have to sharpen them before you start using them?

Do lawn mower blades come sharpened?

Almost all new lawnmowers and lawnmower blades come pre-sharpened from the factory and there is no need to sharpen them before you can use them. Even if the new lawnmower blade that you just bought seems a bit dull it is already sharpened at the right angle for cutting grass, and it is already exactly as sharp as it needs to be.

While a new lawnmower blade doesn’t need sharpening right off the bat when you just buy it you will definitely have to keep an eye on how smoothly your lawnmower is cutting the grass. If you notice that the grass is being torn or shredded instead of being cut after you run your lawnmower over it, it is a sign that your lawnmower blade is dull. This article will tell you all about how sharp a lawnmower blade should be and how to sharpen it if it seems dull.

How Sharp Should a Brand New Lawnmower Blade Be?

It is important to remember that a lawnmower’s blades don’t require a very sharp edge to cut the grass. In fact, the ideal sharpness for a lawnmower blade resembles that of a butter knife instead of having a very sharp edge. Sometimes new lawnmower blades might have a protective coating of paint on them which automatically comes off after you start mowing the lawn with them. Lawnmower blades cut grass with the help of the high speed they are rotating at instead of their sharp edge. Having a very sharp and thin edge would not last more than a few uses before it would have to be sharpened again so a blade that is sharpened at between a 40 to 45-degree angle is considered sharp and ready to cut grass. If you decide to sharpen a lawnmower blade more than the recommended angle it will require you to sharpen your blade quite often (after every few cuts) because after a few uses the overly sharp edge will return to its factory sharpness.

How Do You Sharpen a Lawnmower Blade?

A telltale sign that your lawnmower blades need sharpening is by taking a close look at the leaves of the grass after you have finished cutting it. An ideally cut grass should have a sharp edge and the edges shouldn’t be uneven or torn because having a torn edge leaves the grass vulnerable to diseases as it takes a lot of time for the grass to repair the damage from a dull blade. Another sign that your lawnmower blade is dull is that your lawn will seem unevenly cut and the grass will be taller in some areas while short in others. If you notice that the thickness of the edge of the blade has been reduced drastically and they seem paper-thin then it is time to replace the blades. If the edges of the blades are still thick and it just seems dull you can sharpen it up by following the steps below:

Step 1: Take Precautions:

Safety first you have to make sure you don’t accidentally injure yourself if the lawnmower starts while you are removing the blade for sharpening.  In order to prevent this, disconnect the sparkplug wire from the sparkplug before you flip the mower on its side to remove the blades.

Note: Spark plug is located on the side of most lawn mowers but if you can’t find the location of the spark plug refer to the user manual to confirm its location. Also, make sure that any other power sources are disconnected before you start the process.

Step 2: Tip the Mower to the Side:

Make sure that you flip the lawnmower on the side with the carburetor and the air filter facing upwards to prevent any engine oil from leaking into the carburetor or the air filter. Once you have the lawnmower on its side use some paint or a pen to mark the lower side of the blade. This will make sure that you don’t put the blade back on backward. It is also recommended to run the lawnmower until it is completely out of fuel before you flip it to the side.

Step 3: Remove the blade:

Now grab some safety gloves to keep your hands protected from any cuts and use a piece of wood to secure the blade in place by jamming the wood between the blade and the deck to prevent it from moving when you try to open the bolt with the wrench. Next, take a wrench and unscrew the bolt in the middle of the blade to take the blade out.

Step 4: Sharpen the Blade Correctly:

Clean any pieces of grass or rust from the blade before securing the blade with a clamp. Now run a metal file along the edge of the blade.  Your goal is to sharpen the blade at the angle it already has which should be between 40 to 45 degrees or you can refer to the user manual to find out the correct angle. The goal is to get a shiny and even edge not to make the edge pointier.

Step 5: Reinstall the Blade:

Before reinstalling the blade into the lawnmower make sure to apply some WD-40 to the bolt of the blade because the bolts that hold lawn mower blades in place tend to rust over time so apply a lubricant will help prevent any premature rusting. It is important to install the blade correctly with the side you marked when taking the blade off facing downwards. Installing the blades incorrectly will result in loss of cutting ability of the lawnmower.

Other than sharpening the lawnmower blade you would also want to make sure that the blades are balanced. Unbalanced blades will cut the grass unevenly and the vibrations can also damage the motor of the lawnmower. To balance out the blades of a lawnmower, you can either use a balancer which is a device specially designed to balance lawnmower blades. Or you can balance the blade manually by placing it on a flat wooden surface and notice if either is raised upwards or not. If one of the sides is tilted upwards then the side of the blade that is resting against the surface is heavier and you will need to use a file to remove the metal from it until both sides weigh evenly.

How Often Should You Replace Lawnmower Blades?

If your lawnmower’s blades are badly damaged or the useful edge is worn beyond repair then it is obvious that you have to get new blades. Some common kinds of damages that are found in lawnmower blades include cracks and curved edges. Generally, you will need to sharpen your lawnmower blades after every 25 hours of use. You can make a set of blades last a lot longer than a year if you don’t use your lawnmower very often. Moreover, some lawnmowers might have different recommendations for when their blade needs to be replaced and it is better to follow the manufacturer’s recommendations.

But if you have lost your user manual it is a good rule of thumb to replace your lawnmower’s blades every 200 hours of use. How long you should be using a set of blades depends on many factors and a very high-quality lawnmower blade is going to last you for 400 hours of use easily. So it is a good idea to keep an eye on the condition of the blades and how well your lawn is being cut to give you an idea about when to replace them. A severely damaged blade can break during usage and can injure someone or damage the lawnmower itself.  

Final Remarks

Most people who buy a new set of blades for their lawnmowers often think that they have to sharpen the blades before they can install them into their mowers. But as we have elaborated above that a lawnmower blade doesn’t have to be razor-sharp to cut the grass and if you sharpen the blade of your mower too much you can potentially cause it to become overly thin and get damaged easily. While it is true that a very sharp blade will cut the grass better, maintaining a sharp blade will require constant sharpening so save yourself the hassle and only sharpen the blade twice a year to keep your lawn properly maintained.