How to Sharpen Lawn Mower Blades
It's a good idea to sharpen lawn mower blades every four to six weeks.
Your lawn will tell you when they need to be sharpened. Dull mower
blades tear, shred and bruise grass leaves. The frayed leaves will turn
brown and then white, making your lawn look ugly. Sharp blades cut
cleanly, leaving your lawn looking manicured.
Tools You'll Need:
- 12" Mill File, Bench Grinder or Angle Grinder
- Bench Vise
- Block of wood and C-clamp or a Blade Holder
- Wrench to remover blade
- Blade Balancer
- Spare Blades (optional)
Keep a sharp, spare blade on hand. Then you will have the option to
swap the sharp blade with the dull one - And then sharpen the spare at
your convenience. A spare lawn mower blade will cost you about $15.
||Bad example! Don't use your hand to hold the blade like I'm doing. Use a Blade Holder or a 2x4 clamped to the deck to hold the blade.
Clamp your blade in a vise.
||The best way to sharpen lawn mower blades? Use a flat file. Grinders take off too much material and will weaken the metal if you are not careful. Be sure to follow the factory bevel.
Sharpened lawn mower blade
Use a blade balancer to check the balance.
I picked up this blade sharpener that attaches to a drill at Home Depot for about $7. It works pretty good. However, it's easier to keep the correct angle using a flat file.
Sharpening Lawn Mower Blades
- Remove the blade. Work safely and keep all your fingers - disconnect the spark plug wire to make sure the engine does not accidentally start. When
tilting your mower on its side, make sure the side with the air filter
is on top. This will keep oil from draining into the carburetor and
saturating the air filter.Spray some WD40 on the
blade bolt and give the penetrating oil a few minutes to work its way
into the threads. Then mark the bottom of the blade with a Sharpie to
help you re-install it properly.Inspect the blade after you remove it. Cracked or bent blades need to be replaced.Cleaning grass build up around the center bolt hole of the blade will guarantee a tight fit when you remount the blade.
- Sharpen your blade with a grinder or file. OREGON makes a nice lawn mower blade sharpener - Lawn Mower Blade Grinder Pro Series (See all Mower Blades & Sharpeners) it costs about $700. There is a drill bit grinder
that sells for $7 at Northern Tool, Home Depot, Amazon.com, and other
hardware stores. You can pick up a mill file for $5 and they work as
well or better than a grinder.Clamp into a viceSharpen with a bench grinder, hand-held grinder or flat file. Be sure to follow the factory bevel.It
is quicker to use a grinder if your blade is really dull and full of
nicks. However, you don't have to grind all the nicks out - just get a
sharp edge.Be careful if you choose to use a
grinder, they tend to remove too much material quickly and will overheat
the metal - weakening the mower blade. Keep a bucket of water on hand
and cool the blade by dipping it in water frequently.If
you sharpen your lawn mower blades every couple of weeks, simply run a
metal file along the cutting edge - file toward the sharp edge of the
blade while maintaining the correct angle. Remember, files remove metal
on the push (or forward) stroke - lift after each stroke. Use the file
on flat side to knock off any burs left by sharpening.When sharpening, try to take an equal amount of metal from both ends of the blade to keep it in balance.
- Balance the blade - your mower will run smoother. An out of balance blade will cause severe vibration that will damage your mower engine. Use a blade balancer (most hardware stores carry them) to check the balance. File metal off of the heavy end to reduce weight.
- Re-install the blade
- remember you now have a very sharp blade, install carefully. If you
marked the bottom of the blade you should have no problem installing