If there is one subject that people love to discuss when it comes to mowers, it’s the best angle to sharpen a lawn mower blade. Rather than joining the debate, I’ve pulled out the good stuff from the manufacturers, saving you from the minefield of information. This article will explain the proper angle to sharpen your lawn mower blade to, as well as explain why the angle of your blade edge really matters.
Knowing the Proper Angle to Sharpen Lawn Mower Blades To
Firstly, it 100% matters that you sharpen your blade to the correct angle. The industry standard for a lawn mower blade is 30-degrees for a flat blade. As with all things in life, there are exceptions. The best way I’ve discovered to check your blade cutting angle is to use a lawn mower blade angle gauge. Let’s look at some different blade angles you may come across or even have on your mower.
15 Degree High Lift Blade
These blades produce greater airflow lifting the clippings into the mower deck using the twist in the blade. With this high lift, these blades are ideal for those who bag clippings.
30 Degree Standard Blade
The standard blade, in my experience, is the best all-around blade. The steeper blade angle provides more durability to the cutting angle and they still usually have a 2-3 degree twist to lift the grass into the deck and give it sufficient airflow to allow for mulching.
45 Degree Blade
This type of steep angle gives excellent durability and allows you to take on some heavier foliage. This is typically a great choice of blade if your lawn type has a more significant structure and you don’t want to create lift. This is also the ideal blade for cutting sandy areas where you want to limit the airflow.
Combination Blades
Some blades have a combination of different cutting angles that pull the best elements from different blade types; having both 15 & 30-degree angles on the same blade is very common. These blades are often referred to as 2-in-1 and 3-in-1.
How to Ensure You Get the Right Angle When Sharpening Your Blade
If we discuss how to sharpen a lawn mower blade, there are a few different ways, depending on whether you can remove the blade or need to sharpen the blade without removing it.
First, you’ll need to know the angle. A common mistake is measuring the wrong angle. So let’s check how to read the correct angle.
Which Angle Do You Measure
The correct angle to measure is the angle within the blade. Place a lawn mower blade angle gauge over the blade, and then use the underside (land-side) and cutting edge as your reference surfaces. When you measure this it should be somewhere around the 30-degree mark if you’re using a standard blade.
Not The Result You Were Expecting?
Suppose you don’t get the result you were expecting. In that case, there could be several reasons:
- You’re Measuring the Wrong Angle
- You’re Using the Lawn Mower Blade Angle Gauge Incorrectly
- The Blade is Extremely Dull
- You’re Using a Non-Standard Blade
Firstly, check that you are measuring the cutting angle and not the back side of the blade. Then check that your gauge is reading the acute angle. Some gauges will show different angles depending on the starting angle. Make sure that your starting angle is 0 degrees. For example, if you start with 180 degrees, you may be getting a result such as 150 degrees. Don’t worry – this has made me scratch my head a few times too!
If you happen to get a reading lower than 30 degrees (used blade), the blade has probably worn down significantly during cutting. If this is the case, you can just round up to 30 degrees.
Considering a non-standard blade for a moment, you’ll need to work out what these angles started at. Bear in mind that blade angles decrease as they wear out. So, if you get a reading of 41 degrees, it would be logical to think that it probably started at 45 degrees, and if you discover it’s 12 degrees now, then this probably started at 15 degrees. As we discussed earlier, a combination blade may include two different angles, so just take your time and measure both.
Lastly, a note worth mentioning is that you can change a blade to whatever angle suits you best. If you happen to have a 35-degree blade, you can alter this to 30 degrees. If you choose to alter your blade’s angle, just keep it within the 15-45 degree range. Doing this too many times will result in the blade disappearing very quickly.
Best Reference You Can Get is to Check a New Blade
If you have a new lawn mower blade that is unused, it’s a good idea to check it before using it, as this is the most accurate reading you will get.
How to Properly Sharpen Lawn Mower Blades
It’s crucial that once you know your angle, you can properly transfer it to the blade when sharpening your mower blade. My favorite methods to sharpen a lawn mower blade are to use either a metal file, angle grinder, or bench grinder. These methods, in my experience, give me the best results and make for an easy transfer of the desired cutting blade angle.
It’s also important to use the right grit for the job. I find 60-grit to be the best grit for sharpening lawn mower blades.
Why It’s So Important to Get the Proper Blade Angle
Look at this from two angles (excuse the pun). Firstly, from the point of view of the lawn and secondly, from the lawn mower’s point of view. An incorrect cutting angle on your lawn mower blade is similar to using a dull blade or even cutting wet grass. Here are some of the issues it can cause and why knowing the best angle to sharpen a lawnmower blade is essential.
Torn Grass
When the blade has the incorrect angle, it will be unable to cut cleanly and tear the grass apart, which has a number of undesirable impacts (see below).
Ragged Finish & Uneven Cut
As a result of the torn grass, the finished result will be less than perfect. Even more so if you use a low lift blade. In addition, patches of uncut grass will likely be seen throughout the lawn.
Browning of Leaf Tips
Grass that is torn as opposed to cut will begin to turn brown after a few days due to the damage caused.
Overstressed
When cutting your lawn, the plant immediately reacts with shock, focusing its energy on recovery. Tearing the grass can put immense stress on the plant and cause such problems as slowed growth, shallow root systems, and even cause the grass to die in the most severe cases.
Increased Risk of Disease
With the stress and open wounds created when grass is torn, its ability to fend off various lawn diseases is diminished. And lawn diseases can be a pain to deal with (+ costly too).
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