Sharpening Your Lawn Mower Blade is an important part of keeping you grass healthy. For the average homeowner, this should be done once or twice per year. Here are some of the tips that can help you in 2021.
Does My Blade need to be Sharpened?
Failure to properly sharpen your blades will rip the top of the grass instead of cutting it. So to see if you need to sharpen your blade you will have to get really close to the ground and inspect the tips of the grass. It should be cut cleanly. If you see the tips of the grass torn (see below) then you are exposing the grass in a way that kills the color of the overall turf.
Before you turn you mower over or climb underneath, a few safety precautions need to be taken. Firstly - disconnect you spark plug(s). Get the proper tools (consult your operators manual) and remove the blade(s)
Look at the blade closely. If you are missing chunks of the blade, or if it is bent, then take it to the nearest small engine shop and get a new one. A damaged blade is not safe to reuse! The good news is that you will not have to sharpen a new one.
Put the blade on a vice. Using a grinder or coarse file follow the angle of the cutting plane on each leading edge of the blade. Grind or File this plane using the same angle. It is important to have the very edge of the blade to gently grab the skin on you finger when you lightly press on it. Don't have the expectation of having it as sharp as a steak knife. The sharper the edge, the quicker it will dull. When you get there, turn the blade over and lightly grind/file the bottom of the leading edge to get off the burrs.
An unbalanced blade will cause vibrations that can damage your engine. A simple way to check for balance is to hang the blade on a nail on a wall. It should remain how you hang it. If it rotates, then take more metal off the heavy side until it balances.
Always remember to put the blade back on the mower with the newly shiny, sharpened edge facing towards the engine. Tighten the bolt(s) to the specified torque. Reconnect the spark plug and get back to mowing. Make sure to check your freshly cut grass to see if the problem has been solved.