Lawn Mower Blade Sharpening
Lawn mower blades are hard. They have to be because of the tremendous beating they take. Metal hardening is a critical issue with manufacturers because if the blade is too hard it become brittle and will crack or chip when it encounters a stone or practically any hard object in the grass. On the other hand, if the blade is too soft, it will dull easily and need regular sharpening which decreases the life of the blade.
When you take your blades off for sharpening, take a good look at them and try to determine what their inherent weakness may be. If they are bent or very dull you may want to try another brand of blade. If they are cracked or chipped, you may want to try antother brand also. Switch brands once in a while until you find one you are happy with. All blades are not equal.
Sharpening lawn mower blades is somewhat critical too. The very best way to prevent damage from the sharpening process is to place the blade in a steady, bench-mounted vise and use an aggressive file to resharpen the edge. It takes a long time and many of you may not have a vise. Be sure to wear heavy leather gloves while sharpening because just one slip and you can get a mighty nasty cut.
What about using power tools? Well, it makes sharpening a lot quicker but if you do not control the heat, you will soften the blade and it will then experience a short, short useful life. Here is a method that does work though – keep water running on the blade and don’t sharpen but a few seconds at a time. Even with the down time for cooling, it is much quicker than sharpening with a file.
Here are photos of a pair of blades I sharpened with a power grinder with a “flapper” sanding disk attached. The blades were fastened securely in an outsed vise and water from a water hose ran over them constantly. I checked every 20 seconds or so for heat. If the blades get too hot to touch, you’ve already gone to long. Alternate between 5 seconds of sharpening and 10 seconds of cooling. Take your time and you can get lawn mower blades sharp like these: