Asking how often to sharpen lawn mower blades can be a controversial topic. You ask 10 people and get 10 different answers. In my experience, through trial and error, I’ve learned how often I need to sharpen my mower blade to achieve a great cut every time, and what to watch out for. In this article, I will strip back the misleading information and leave you with just the facts. My tips will hopefully teach you the signs you need to recognize to determine how often to sharpen your mower blades, allowing you to leave the guesswork to others.
The General Rule About How Often to Sharpen Mower Blades
Every 25 hours at a minimum, but this is definitely not a universal rule. 25h would only really apply if you are cutting in ideal conditions. Numerous factors, which I’ll talk about below, will result in you needing to sharpen your mower blades more often.
Factors that Affect How Often You’ll Need to Sharpen Your Mower Blade
New blades will naturally lose their cutting edge over time. Different manufacturers use different source materials and different designs, so no two blades will wear down at exactly the same rate. For this reason, and a lot of other factors, there isn’t a universal answer to the question of how often you should sharpen your mower blade.
Have a look through the list and see some of the variables you should be aware of that will affect the longevity of the blade’s cutting ability even before you begin to cut.
Design of Blade
Different blades have different designs. For example, if you happen to have 15-degree lift blades, these will require sharpening much more frequently than, say, a blade with a 30-degree angle due to the nature of the thinner profile.
Blade Material & Quality
Mower blades are typically manufactured from various types of steel (carbon steel, boron steel, even stainless steel sometimes) nowadays whereas in the past iron was the go-to material. Some of these materials are more resistant and durable than others, and will therefore last longer.
Type of Grass
Now, if you have ever cut Zoysia grass and Floratam you will know that your grass species makes an enormous difference. In my experience, Zoysia is super tough and needs to be cut with a good, sharp blade, whereas Floratam can still be cut effectively even if your blade has a fair bit of wear. So if you have a grass type like Zoysia, you’ll be sharpening more frequently.
Zoning (Sand v Dirt)
Lawns grown on a nice bed of topsoil won’t feel the negative effect of zoning, but if you happen to be in a sandy area, then every time you mow, you’ll be lifting the sand and grinding off the edge on your blade. Sandy soil is very abrasive!
Weather (Wet v Dry)
We all know we shouldn’t be mowing in the wet, but there are occasions when we have no choice, especially those who cut lawns for a living. A wet lawn itself isn’t such a problem; it’s the grass clumping in the deck that’s the problem. Blades cutting through great wads of grass and dirt has the same effect as sandpaper on the blade.
6 Signs that Tell You When to Sharpen Lawn Mower Blades
Here are some easy indicators to watch out for to help you determine exactly when your mower blade needs sharpening.
Torn Grass
If you suspect your blade needs to be sharpened, but you’re not 100% sure, you should look at the grass. If it’s not a clean-cut and the grass is torn, it’s very likely that the blade has lost its cutting edge and needs to be sharpened.
The Lawn Changes Color
A day or two after mowing, torn grass will change in appearance, and you might notice a brown discoloration on the lawn. This is where the torn edge browns off. If you didn’t notice the lack of a clean cut initially, you will at this point.
Your Mower is Missing Grass
Your mower may be struggling to cut the grass, leaving a lawn with an uneven appearance behind. If you find that your mower is working harder, it could be down to the blade not having the ability to complete the cut very efficiently, rather like cutting a steak with a butter knife.
You Hit a Rock
If you happen to strike any foreign object other than the grass, such as a rock or tree roots, it’s likely that some kind of damage has been done to the cutting edge and it should be checked. Just in case.
Blade is Full of Chips and Dents
Have a quick look at the blade before you begin to mow or at least before every other cutting session. Even if the blade has been sharpened recently, there could be damage you’re unaware of, such as chips and dents. Any damage to the blade will reduce the cutting power and make your job a lot harder.
Lawn Mower Losing Horsepower
As you know, lawn mowers only have small engines that have very minimal horsepower. Usually, the blade will be specified up to the mower’s capabilities, meaning there’s often a fine line between peak and poor performance. If you ever let the grass grow long, you will likely have felt the mower bog down when cutting due to the engine becoming overwhelmed by the task it’s facing. Dull blades have the same effect on power draw so regular sharpening intervals keep you on the right side of the line.
My Tips to Get More Out of Your Blade (Increase Time Between Sharpenings)
I’ve compiled my favorite tips to help you get more out of your blade and increase the time between sharpening. My best advice is to use all of these tips together. This will give you the best chance of reaching the infamous 25h mark.
- Select the Correct Blade for Your Environment
- Sharpen Blades to the Correct Angle
- Sharpen Blades Using Methods That Achieve the Best Result Even if it Can’t be Removed
- Remove Objects From the Yard
- Plan a Route and Avoid Obstacles
- Mow When Dry
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