Lawn Mower Blade Sharpening
If you prefer that I sharpen your lawn mower blades, my fee is $6.00 per blade. I first check the blade for potential problems. I will not sharpen a blade that is likely to injure you or your equipment.
The Lawnmower Underworld
If you would like to sharpen your mower blades yourself, it is not difficult and the process will give you an insight into the lawnmower underworld. Here are a few things to know.
Avoiding Blade Sharpening Injury
Disconnect the spark plug wire and tie it safely away from the spark plug or remove the spark plug entirely. Wear some heavy leather gloves. Turn on the mower on its side with the carburetor up. For all of you guys that tell themselves “this will only take a minute” or “I don’t need any darn gloves,” A cut from anything on the underside of a mower could be a real problem. There are plenty of microorganisms, animal feces and pesticides in that soil and grass.
Before You Remove The Blade
Check that the blade isn’t bent. Locate a reference point on one side and note the height of the blade tip at that location. Rotate the blade 180 degrees and check the height of the opposite blade tip. There should be no significant difference – say no more than 1/8″ or so. If it is greater, the blade is bent or the crankshaft is bent. Either will require further investigation as running the mower under such conditions will probably result in excessive vibration and can be dangerous.
How To Sew Your Own Stitches
Use a box end wrench or socket to remove the bolt holding the blade on the drive shaft. Use a block of wood under the blade to prevent the blade from turning. Once the nut is loose, unscrew it the rest of the way by hand and remove any washers or mounting plate and note their exact position and orientation. The blade and adapter should come off easily.
Pay close attention to the arrangement of the blade and associated hardware so you can replace everything properly. If the (Woodruff) key was damaged or sheared replace only with a similar soft key. Else, you’ll be replacing the engine next time there is a minor incident.
If you decide to use an open end wrench or adjustable wrench, be prepared for it to slip and damage the bolt head and your hand if you’re not wearing heavy gloves. Turn counter-clockwise. Make sure that if the wrench slips, your flesh will not contact the blade or other sharp sheet metal. Arrange your position and the mower so you are pulling the wrench towards you – this is a more stable controllable arrangement.
Inspect The Blade
Slight nicks and dents can be cleaned up with a file while the blade is still installed on the mower. Unless you have run into something, this is probably all that is needed on an occasional basis. Removing this small amount of metal will also not unbalance the blade enough to worry about.
If the damage is severe, consider replacing the blade entirely – they are not that expensive, $10 and up. Otherwise, you can use a file, a bench grinding wheel, or a grinding wheel mounted in an electric drill.
Since the rotating blade also contributes to proper air flow, you do not want to upset the shape. Sharpen in such a way that the original blade angle is preserved. It doesn’t need to be razor sharp. A 1/64″ edge is fine. Anything finer will quickly be dulled by little bits of stone and dirt.
Safety is the main concern here – if any part of your body contacts the whirling blade, you will be in trouble no matter how dull or sharp the blade might be!