There are a few important reasons why lawn mower blades must always be sharp. Namely because cleanly cut grass blades:
- Suffer less stress than if they are torn by a blunt blade.
- Are less likely be affected by disease.
- Suffer less evaporation in drier conditions.
Not to mention that, if you use a lawn mower with a rotary blade, a sharper lawn mower blade:
- Helps the blade rotate faster, which also tends to give a cleaner cut.
- Saves gas or electricity, or makes battery powered mowers run longer.
By the way, be sure to have a look at our page on Lawn care.
Lawn mower types
Basically, there are two lawn mower types: rotary and reel. All rotary lawn mower have powered blades and most reel lawn mowers are not powered.
Rotary lawn mowers
These are the most popular. They can be gas powered, electric or run on batteries (see our page on cordless lawn mowers). They can be quite simple, push style machines, they can be self propelled, or they can be riding lawn mowers. They can simply mow grass, or they can mow and mulch grass at the same time (see the section on ‘Mulched organic matter’ on our page on Green fertilizers).
Typically, when you buy a rotary lawn mower, it comes with its own blade. If you buy a quality lawn mower, chances are that it will be outfitted with a quality blade. The opposite is just as true. Quality blades are usually made of metals that stay sharper longer. Plus better blades are often straighter and better balanced, which means the mower is more efficient and vibrates less.
Reel lawn mowers
Reel lawn mowers have multiple blades that work a bit like scissors. The grass gets cut off as the moving helix shaped blades pass over a stationary bedknife. Reel lawn mowers can be a very good choice, if you tend to mow your lawn very regularly and quite short. It may not be as good a choice, if you want to keep your grass lawn a bit longer.
These lawn mowers can have seven blades or more, but they have a single bedknife. The blades are not meant to be replaced, but the bedknife can be changed. Both blades and bedknife may be sharpened, on the other hand. Since reel lawn mower blades are more complicated to sharpen, it may be a good idea to buy a better quality model.
Rotary lawn mower blades
Rotary lawn mower blades made of steel alloys, such as high-carbon, nickel-alloy steel, are extremely hard, and therefore resist wear and remain sharper longer. Hardened steel blades are also more resistant to wear than standard blades.
Mulching blades are shaped so as to lift, mow and mulch grass blades. Specialty blades may offer better mulching, or create a succion effect (known as Lifting blades), which may be quite desirable with longer lawns.
Sharpening lawn mower blades
Cheaper lawn mower blades need to be sharpened quite regularly. And although quality blades should typically stay sharper longer, they also need to be sharpened every so often. As they hit small branches, pieces of bark, and pebbles, all lawn mower blades loose some sharpness. The more often you pass over such debris, the more often your lawn mower blade will require sharpening.
- Rotary lawn mower blades are quite simple to sharpen. You can do it yourself using a lawn mower blade sharpening kit, or you can take your blade (or your mower) to a shop where they sell and sharpen lawn mower blades or knifes. Whether you do it yourself or have someone else do it, you must ensure that the blade is well balanced once it’s been sharpened. An unbalanced blade will generate unwanted vibrations. You must also make sure the blade is securely locked in place once it’s been reattached to the lawn mower. You wouldn’t want it to go flying out as you mow your lawn.
- Reel lawn mower blades are more complicated to sharpen. For such lawn mowers to cut grass cleanly, both the helix shaped blades and the bedknife must be sharp, so that’s a lot of blades to sharpen. Plus helix shaped blades are not as easy to sharpen as straight lawn mower blades. Finally, once all the blades have been sharpened, you must ensure that all the helix blades pass over the bedknife in just the right way. In other words, sharpening reel lawn mower blades is no simple task, so if you don’t know what you’re doing, you should probably leave this job to specialists.
Replacing lawn mower blades
Rotary lawn mower blades can be replaced easily. They may be purchased in specialty stores or over the Internet. If you do decide to change your mower’s blade for a new one, make sure that you find a blade that is perfectly suited to your mower.
Reel lawn mower helix blades are cannot typically be changed. The bedknife may be changed, on the other hand.