The easiest way to tell if your lawn mower blade needs sharpening is to look at the ends of the blades of grass on your lawn. If the edges seem torn and jagged and they show white or brown tips then you know the blade needs sharpening.
Sharpening your lawnmower blade isn’t that difficult to do but you can also take your blade off and get it sharpened at a repair center or bring your whole lawnmower in to be serviced. Some local service centers offer a maintenance program where they change the oil and sharpen your blade. But the job isn’t that difficult and you don’t need to take your blade off to do it.
The first thing you want to do is remove the spark plug wire and put a piece of masking tape over the end of the spark plug so the engine has a lesser chance of starting while you work on it.
Tilt the lawnmower on its side with the gas fill cap on the up side so gasoline won’t leak as you work.
The next thing you want to do is clean off the underside of the lawn mower with a hose and brush if you have one. You don’t really need to clean much more then just the blade but its a real good time to do it and it will make working on your lawnmower much easier.
Soak the bottom well and come back and wash off the grass.
Put on Gloves to protect your hands while working.
Wedge a block of wood between the blade and the housing so it can not move.
Now inspect the blade for any damage. If you hit a rock or stump it can put gashes in the edge of the blade.
If the blade is bent or has heavy damage you should most likely replace it. The cost of a new blade is not that much and you can not repair a bent blade.
A bent or out of balance blade can make your engine vibrate and will eventually cause internal engine damage.
Using a file you can sharpen the blade while it is still attached but check your manufacture’s directions often it is recommended to remove the blade. Follow their instructions not mine here.
If the blade needs extensive sharpening to remove damage then you want to take the blade in to be sharpened and make sure that they balance it.
If you do not want to pay to have the blade sharpened and balanced and a simple hand file won’t be enough then buy a new one. It is better then buying a new engine.
If you need to remove and replace the blade never replace the bolt with anything other then a manufacturers bolt because they are special hardened steel.
Tighten the blade to manufacturer’s specifications which should be about 50ft pounds.
Remove the blocking wood and return the lawnmower to its upright position and then reattach the spark plug wire.