When you’re mowing the grass, whether or not you have sharp blades will make a big difference in the quality of the cut, and by extension, the look and health of the yard itself. How often and when lawn mower blades should be replaced will depend on the wear and tear the season puts your mower through (rocks and sticks hidden in the grass are a familiar surprise to lawn mowers!)
Whether you should sharpen your lawn mower blade or buy a new one will also depend on the usage. Maintaining a regular schedule of sharpening and replacement will keep you clear of the disadvantages of dull mower blades.
How Do Lawn Mower Blades Dull?
A blade will dull at different rates, based on how often it’s used, how much grass it covers, and the hardness of the material it’s made from. The cutting edge of the blade will wear down over time as it comes into contact with the grass, and it will wear down faster when it comes into contact with harder objects.
How Do I Know If My Lawn Mower Blade Is Dull?
There are signs on both your lawn and on the blade itself that help you know if your mower blade has dulled. If you notice uneven patches in your lawn after passing the mower over it, or you see that the single grass sprouts look ripped rather than sliced, it’s time to inspect the mower blades.
If you have a push mower, you can easily flip it over to inspect the blades. The edge should be sharp enough not to gleam with light; if there’s a reflection along the edge, that part of the edge has smoothed and could use a sharpening. A riding mower can’t be turned over, but you can inspect the blades according to the model of mower you have.
How Many Times Can You Sharpen Lawn Mower Blades?
If this is the blade’s first or second time dulling, it can be sharpened to extend its life. Whether you have a blade sharpener yourself or take it into a shop, it’s recommended to sharpen lawn mower blades every 20 hours of use or every three to four months if you use it once or twice a week.
This usually turns out to be two or three times a season for a sharpening: at the start of the year’s use in spring, once in the middle of the summer, and, with heavy use, again towards the end of the summer. In total, you shouldn’t sharpen a blade more than four times before replacing it.
Is It Worth Sharpening Lawn Mower Blades?
A sharp blade extends the life of your mower because a dull blade requires more work from you and the machine over time spent redoing areas or mowing more frequently due to ineffective cuts.
Since you can sharpen a blade up two or three times a year, it’s worth maintaining a schedule for sharpening and replacement to keep your grass cuts clean and efficient.
When To Replace Lawn Mower Blades
You will know if your push mower blades are in need of replacement if you can see knicks, gashes, or erosion on the edge of the blade. Fractures in the blade are a sign that it shouldn’t be used and needs to be replaced. If you don’t see these, but you’ve already sharpened the blade a few times or have used it for over a year, it’s a good idea to start thinking about a replacement.
How Often Should Lawn Mower Blades Be Replaced?
Most manufacturers suggest replacing a blade after a total of four sharpenings or after two years of use at most to be sure the metal is of high integrity and won’t chip or break.
This is a matter of safety as much as it is a concern for the quality of cut since broken pieces of metal can injure the person mowing, or people in the vicinity, by throwing or leaving behind broken pieces of metal.
How Do Dull Mower Blades Affect the Health of Your Grass?
The average homeowner will notice the signs of an unhealthy lawn, but it’s not always apparent that it might be linked to the condition of the lawn mower blades. An uneven cut across the property is easy to notice, but the damage done to the grass itself might not be so easily connected to dull mower blades.
Grass recovers more quickly from a clean cut than a dull tearing. Some of the negative effects of dull lawn mower blades on your grass can include:
- Yellowing or browning from damage to the grass blades (leaves) that prevent them from performing enough photosynthesis to develop food
- Thinning in patches from insufficient photosynthesis
- Fungal diseases taking hold in the open wound of the torn blade of grass
- Vulnerability from a weakened condition to stressors like heat and pests