Some time ago I was in a hardware store and an associate told me I should bring in my mower blades to have them sharpened as they “had a machine to make them razor-sharp.” I remember thinking, “Why would I want them to be razor-sharp? It’s a lawn mower for crying out loud. I’m not shaving with it. I am essentially trying to achieve the same look on my lawn as a pair of goats could do.”
So, here’s a quick article to show you how to sharpen your lawn mower blades to a reasonable honing. Considering you are cutting a plant which rabbits nibble, your 6.5+ HP engine with blades spinning at 3,600 RPM is probably on the side of overkill.
How to Sharpen Lawn Mower Blades
There is one rule I always follow when dealing with sharpening blades of any type: Leather Gloves, Always! Whether you are using this technique on mower blades or a machete, put on a pair of heavy-duty leather gloves or some other kind of protection.
Tools You’ll Need
The tools you need. A metal file, leather gloves, and a vice.
- Leather Gloves
- Metal Flat File or Bench Grinder
- Socket Wrench
- Hammer\Mallet\Wood block
- Bench Vice
Step 1: Turn the mower upside down and take the blade off
Some folks will tell you that turning the mower upside down is bad, as the oil will go to places it is not supposed to. I usually do this at the beginning of the season and my oil has already been drained. However, I have done this before with oil in the engine and as long as I let it sit upright and settle for a while, there have been no issues.
Use the socket wrench and appropriate socket to get the work done.
Hint: The bolt is screwed in like normal (righty-tighty, lefty-loosey), but since the blade also spins it can be a pain to loosen. I find it helpful to use a block of wood or hammer to hit against the blade while I hold the socket wrench (gloved of course), rather than trying to torque down on the wrench and a potentially sharp blade.
Turn the mower upside down, preferably after you have drained last years oil and gas. Remove the blade with a socket wrench.
This mower blade is pretty bad off.
Step 2: Place the blade in a vice and sharpen with a file
I have two types of blades for my different mowers: one is a mulching blade (with the extra curve) and the other is a regular blade. The process for sharpening either blade-type is the same.
Run the metal file across the blade and away from you, at an angle, filing on the forward stroke as in the video and pictures shown below.
Note: If using a bench grinder, be careful how much metal you remove (See the next step on leveling). It can be easy to try to remove any imperfections in the blade which may remove more metal than necessary. This is fine as long as you keep both sides the same weight.
Run the file across the blade at an angle and away from you. Place pressure on the file on the forward stroke.
The angle of the file can be determined by the existing edge of the mower blade. Only one side needs to be sharpened.
Step 3: Repeat on the other side and check the balance
While I don’t believe your blade has to be razor-sharp to get the job done, it does need to be balanced. An unbalanced blade will lead to unwanted vibration and noise as well as increasing overall engine\mechanical wear. If you don’t have a handy tool for checking the level of your blade, just rest the blade across your finger, like checking the balance of a good knife. If you have severe leaning on one side, you will need to take off more metal, which means more filing.
Check the mower blade for levelness by using a tool which you can pick up at any hardware store in the mower section.
Step 4: Reattach the blade
Put the blade back on the mower the same way it came off. The concave side of the blade faces the grass. Be sure not to over tighten the bolt; you’ll have to do this again next year!
Happy Spring!
– Yarbrough