Jul
09

Basic Mower Blade Information

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John Deere Mower BladeThere is more to a mower blade than most people realize. At first glance they seem overly simple, yet there is a lot going on here with that single blade of steel. I will not get into the engineering details of material selection, hardness, or other specifications here. But, what I will cover is some important basic details that one should know about in order to properly care for their blades. I am not going cover all the blade types, high lift, mulching, and such. If properly maintained you will have a smooth running and cutting blade. The blades and the deck need to act as one to lift the grass, cut it, and then discharge it.

Let’s first discuss a brand new blade and its cutting edge and length. Have you ever noticed when looking at a new blade the cutting edge is what would appear to most of us not sharp? This cutting edge and angle is actually at the perfect configuration for a clean and smooth cutting blade. Contrary to what most of us think, the cutting edge does not need to be razor sharp. In fact, a slight 1/32 blunt face will cut just fine and actually maintain its sharpness longer. The angle of the cutting edge is also important. If it is too steep the blade will not cut the grass, but tear it instead. If it is too shallow, it will dull quickly and not push the grass around to the deck discharge chute efficiently. This is why it is important to maintain the cutting angle when you sharpen your blades. Also, blades are measured diagonally from cutting tip through the mounting hole center to opposite cutting tip.

Now, let’s talk blade sharpening. The first thing I do after removal is to thoroughly clean the blade of all old dirt, grass, and grime. I then inspect the blade for wear and straightness. If bent, I straighten it if I can. If not, it is time for a new blade. I then clamp the blade in a vice and use a 4 inch angle grinder with a flap wheel. I have found this to be the easiest and fastest way to sharpen blades. As mentioned earlier, you must maintain the cutting angle and it does not need to be a razor sharp edge. Once both cutting edges are sharpened you need to check balance. This can be done with a very inexpensive balancer or something as simple as a nail in a vice. You of course will need to remove material from the heavier side to get good balance. If you ignore balancing, you’ll find you will have a very rough running deck. Not to mention you may experience prematurely replacing spindle bearings. Make note that each time you sharpen your blade you are also making it shorter.

One other thing you should be aware of when inspecting the blade. Make sure that the turned up wing behind the cutting edge is in good condition. If the undercut is excessive, you’ll have a very dangerous situation where the wing could become a flying projectile.

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