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When to Sharpen Lawn Mower Blades?

Lawnmowers are indispensable homesteading machines. Whether you want to cut overgrown grass in your backyard garden or cut turf in your compound to size, having the best one is crucial. But apart from having a STIHL RMA 443TC mower, Husqvarna Automower 450X, or any other top lawnmower brand, several questions come to mind. For example, do you know how to maintain these machines so that they are always in great working condition? Also, how often should you sharpen the blades of a lawnmower?

When to Sharpen Lawn Mower Blades?

When to sharpen your lawn mower blade depends greatly on the quality of the blade and how long you are using it. In general a lawn mower blade needs sharpening after 100 to 400 hours. There are several indicators like torn or rugged grass that indicate that the blade needs sharpening. Also dents and nicks indicates that sharpening is needed.

(CC BY 2.0) by Ivan Radic

Sharpening routine

While you may have a fixed duration for sharpening, note that you should not sharpen the blade too often. First off, the type of a mower blade on your machine plays significance in determining a sharpening routine. Also, the condition of the blade, especially after several hours or weeks of mowing always plays significance. We emphasize physically examining the blade on your mowing machine to determine its sharpness. The presence of nicks and bends means it is time to get your mowing blade back to its optimal working condition.  Most importantly, the material with which a lawnmower blade is made will also determine the frequency of sharpening.

For most people, a standard practice that comes with sharpening mower blades is doing so every 25 hours. It is especially necessary if your machine has rotary blades. Moreover, the conditions under which you mow may occasion a frequent or less often blade sharpening routine. In instances where you take about an hour or less mowing your lawn, we recommend sharpening the blades after every 25 to 34 sessions. The catch here is that prolonged use of lawnmowers subjects their blades to a lot of endurance hence get blunt faster. On the contrary, short mowing durations do not subject the blades to a lot of damage.

If you are a homesteader looking to learn more about lawnmower blades, this post is for you. We explore everything about sharpening lawnmower blades. Read on as we explore this topic together.

Sharpening Lawnmower Blades: Does Duration Of Use Matter?

One of the many questions people ask about sharpening lawnmower blades has everything to do with mowing durations. While we have indicated that for rotary blades, it is okay to sharpen them every 25 hours, it is noteworthy that most sharp mower blades last up to 200 hours before you can sharpen them again. However, the frequency of sharpening may vary depending on the quality of the blade. While some blade will maintain their sharpness for at least 100 hours, others would last for well over 400 hours.

Most importantly, when using these machines, we emphasize inspecting your lawn beforehand. You do not want to hit stones and pebbles when mowing because they would nick the blade, almost instantly. Something even more worrying is that mowing in stony areas may cause a mower blade to break, thus shortening the lifespan of something you had hoped to serve you for a long time.

Now, bearing in mind how often you should sharpen a mower blade, we did some math when preparing the following table:

Duration of mowing
Frequency of sharpening (sessions)
Frequency of sharpening (yearly)
2 hours of mowing
Sharpen after 10 to 13 sessions.
Sharpen every three to four years.
1.5 hours of mowing
Sharpen after 14 to 17 mowing sessions.
Sharpen every two years
1 hour of mowing
Sharpen after 20 to 25 mowing sessions
Sharpen once a year
30 minutes mowing session
After 40 to 50 mowing sessions
Sharpen once or twice every year
15 minutes mowing session
Approximately after 80-100 mowing sessions
Sharpen two times every year

Signs of a Blunt Lawnmower Blade

Having known how often you should sharpen a lawnmower blade, the next question that comes to mind is how do you know the blade is blunt? The truth is that as opposed to other complications that a mowing machine may develop, identifying a blunt blade is pretty easy. You should always lookout for the following signs:

  • Dents and nicks: Physically inspect the blade on your mower. If it has dents and nicks, it is always that time you sharpened it. While smaller dents are easy to sharpen, bigger bends may mean it is time to replace the blade with a new one.
  • Torn or rugged grass after mowing: You can also find out if it is time to sharpen a lawnmower blade by looking at the cut grass. Torn or rugged grass after mowing means the blade needs sharpening. Clean cuts are only possible with sharp blades. 

Sharpening a Lawnmower Blade: A Step By Step Guide to Doing It Right

First off, if you are getting ready to sharpen the blade of your lawnmower, we emphasize doing it aggressively. However, a point of caution is that it should be not razor sharp. It is because razor-sharp blades will get nicked by pebbles and tough grass faster than you would expect. With very sharp blades you also risk sharpening a blade more frequently thereby shortening its productive life due to faster wear and tear.

Thus far, let’s quickly mention that when it comes to sharpening a mower blade, you should get the necessary items ready. They include a blade grinder, a mower blade, gloves, protective goggles, and even necessary, ear muffs.

● Preparing To Sharpen a Mower Blade

With the items you need for the task ready, the next steps involve doing the following:

  • Clean: Clean the work area by removing any flammable objects/materials.
  • Inspect: Inspect the lawnmower sharpening grinder to ensure it is properly insulated and that the stone does not have a crack.
  • Position: Position the lawnmower’s tongue guards at least a quarter inch from the stone and the bottom guard about 1/8 from the stone. You should not use the grinder if the adjustments are not right.

● Sharpen the blade using a Lawnmower Blade Grinder

If you are looking to use a lawnmower blade grinder for the first time, you must consider the following steps:

Step 1. Determine left/right handed:

Start by determining if your mower is right-handed or left-handed. The grass side or bottom side should be in contact with the surface before start sharpening.  Most importantly, we emphasize checking the blade grinder user manual for details.

Step 2. Adjust the blade grinder:

Next, adjust the blade grinder to the right sharpening angle then set the blade on the grinding table so that it appears to be touching the grinder.

Step 3. Power cord:

You should now proceed to plug the power cord into a recommended power outlet.

Step 4. Set the direction:

Depending on whether the blade on your mower is right-handed or left-handed, set the motor switch in either reverse or forward position. Reverse for left-handed and forward for right-handed variants.

Step 5. Stand in the right place:

You should always stand facing the front of the grinder. Or let’s put it this way. It keeps you safe from sparks and any materials that will get thrown out from the grinder during sharpening.

Step 6. Start sharpening:

To start sharpening, turn on the switch so that the stone and the motor go at full-throttle.

Step 7. Hold with two hands:

When sharpening a lawnmower blade, we emphasize holding the blade with two hands but on the opposite end.

Step 8. 90 degree angle:

Position that blade at 90 degrees so that the grass side faces down.

Step 9. Move the blade:

Move the cutting edge back and forth on the grinding wheel when sharpening it to remove dents and nicks. Having indicated earlier that a lawnmower blade should not be razor-sharp, we recommend that you focus on having a sharpness of 0.045.

Step 10. Sharpen the ends:

You should ensure to sharpen both ends of the cutting edge. Most importantly, pass it along the grinding edge several.

Step 11. Balance the blade:

With the blade sharpened, now use an ideal blade balancer to ensure the sharpened edge is properly balanced. If you notice there is a heavy bend on the sharpened blade, use the grinder to align it. Finally, rid the working area of dust and grit. Also ensure to switch off the grinder, not forgetting to remove the spark pin so that it does not start accidentally.

Should You Sharpen Brand New Blades?

A question most people ask about lawnmower blades is whether it is okay to sharpen brand new ones. Well, let’s categorically state that it is not necessary. You may be tempted to sharpen new blades because they often come covered by a thin layer of the paint coat. However, the coat will always wear off after a few minutes of mowing.

The Bottom Line

There are many downsides of mowing your lawn using dull mower blades such as roughly cut edges and predisposing grass in your compound to diseases.  Thus, at whatever cost, a sharp mower blade is the minimum threshold for any homesteader looking to do a good job. In the end, a good lawnmower should deliver excellent performance all-round even on tough turf.

With proper sharpening using an ideal grinder, and also properly balancing the blade, everything else should be easy. We hope tips on sharpening lawnmower blades as explored in this post will help you do the right thing henceforth.