As part of any lawn mower’s regular maintenance and care, you should sharpen or replace a lawn mower’s blades once or twice every season or so, depending upon how much you use your mower. A sharp mower blade cuts your lawn cleaner while a dull blade can actually “rip” and pull at your grass, actually damaging the plant itself, making your grass turn brown and be more susceptible to disease. A dull mower blade can also force your lawn mower to work harder to cut the same amount of grass, which can actually increase your fuel consumption.
You can actually tell if your lawn mower blades need to be replaced or sharpened by simply taking a good look at your grass after you cut it. If you the ends of the grass blades look ragged (compare it to a few blades of grass your cut with a pair of scissors) or if the ends of your grass blades are turning brown a day or two after cutting, then your blades are probably due to be replaced or sharpened. Obviously, if you accidentally hit something hard like a big rock or metal pipe with your mower blade while it’s running then you might want to replace the blade for safety’s sake. A nicked or unbalance blade can be dangerous and can, in rare cases, actually break while running.
Put on some gloves, find the right combination wrench, and turn to the left to remove your lawn mower blade. Grunt when appropriate.
You can sharpen the blade yourself, but if you go that route you’ll probably need a grinder and at least a little bit of practice and skill to get your blade sharpened and balanced just right. The cost of having your blades sharpened at a mower shop can be anywhere between $15 to $30, which is about what it costs to replace most common lawn mower blades. I usually choose to replace my mower blades because the cost is the same and it’s actually a pretty quick weekend home improvement project once you’ve done it a couple times. I usually choose to replace the blade when I pull my lawn mower out and get it started the first time each Spring.
So put on some heavy duty gloves, grab an adjustable wrench and maybe a rubber mallet. Here’s how you remove and replace most lawn mower blades:
1. Disable the Mower: For safety’s sake you need to make sure your mower cannot start in any way, shape or form. The quickest way to do this is to remove the spark plug or at least detach the spark plug cord so that your engine can’t get a start, even if you hit the ignition switch or manage to pull the cord accidentally.
Blocking the lawn mower blade from turning with a block of wood. The other end of this piece of lumber is tightly wedged into the ground.
2. Remove Any Gasoline or Oil: You’re going to have to tip your lawn mower on it’s side, so that means liquids in your mower, like gasoline and oil, will most likely spill out. You can siphon the gasoline out of your tank easily with an affordable gas siphon or you can simply mow your lawn strategically until you completely run out of gas. Depending upon your mower type, you may be able to get away with leaving your oil alone. I can tip my mower a good bit without spilling any oil, but for some mowers you may not be so lucky. Do not mix your gasoline and oil by using the same siphoning tool.
3. Secure the Lawn Mower and Mower Blade: Now you can put your lawn mower on it’s side. You might want to secure it with some blocks or place it on a workbench so it’s easy to get to. I tend to secure mine with some concrete landscaping bricks. While it’s on it’s side, clean out any dry grass or other debris so you have a fairly unobstructed work area. You’ll also want to secure your lawn mower blade because as your turn the single bolt that holds on your blade you can bet that the blade will turn, too. There are a couple ways to do this, but the most basic is to lodge a two-by-four or block of wood into the mower deck so that the blade turns and then stops and is held against the block. I always set my mower on it’s side in my driveway (easier to spot and clean up any errant oil or gas drips) and then I prop a block of wood against my driveway and the mower deck. It’s kind of crude, but secure.
4. Remove the Mower Blade Bolt: Now you can use a wrench to loosen the nut or bolt holding on your lawn mower blade. It should be a simple “lefty loosey” sort of turn, but you might need to put some strength into it if it’s been a while since your blade was put on. This is where the rubber mallet can come in. You may need to use a combination wrench or press the wrench against the bolt and bang it a few times with mallet. Still not working? I’ve had good luck on all sorts of stuck screws and bolts with Liquid Wrench, but just about any penetrating oil might do the trick. When you do get the bolt loosened and start taking it off, note the placement of any washers because you’ll want to put them back in the same order that they came off. Once the bolt is turning well, remove the block of wood for the blade and loosen while holding the blade so it doesn’t fall on you.
Old vs. New Lawn Mower Blade. It was clearly past due.
5. Replace or Sharpen Your Blade: If you really want to sharpen your blade, go for it. If you want to replace your blade you can now take this old blade to your local hardware store and just find a replacement blade. If you know your mower make and model you can measure your blade with a tape measure and save a few dollars by ordering your lawn mower blade online. You’ll have to wait a few days, but if you aren’t in a hurry you can always order a few extras to have handy.
6. Put Your Mower Blade Back On: Now that you have a new (or sharpened) blade you can put it back on, reversing the steps you took in the last step. Make sure your mower blade is put on with the sharp edge pointing in the right direction and make sure you put your blade back on with all the appropriate washers. Hand tighten and give the mower a spin or two with your hand, to make sure everything is working well.
Okay, you’re done! Flip your lawn mower back over, gas it up, check the oil, attach the spark plug cable and give it a whirl. If you didn’t attach the blade correctly or it’s unbalanced then your mower may vibrate and shake much more than it did before. Even a slight vibration can be dangerous and can affect the long-term durability of your lawn mower, so stop everything and go through the whole process again. You can use a nail that’s driven straight into a wall as a balancing tool, or you can use a little tool made for balancing lawn mower blades. Yes, they have specialized tools for everything now. A new blade shouldn’t need balancing, but a sharpened one might.
Remember: replacing your lawn mower’s blades is one of the many ways you can maintain your lawn mower and keep it running well all year long! When it’s time to put your mower away for the season, don’t forget to winterize your lawn mower properly!