Proper Angle To Sharpen Lawn Mower Blades: Mower Care 101

The proper angle to sharpen lawn mower blades is important to cut grass neatly and efficiently. Have you been sharpening yours because you need clarification about the right mower blade angle?

This guide will teach you the perfect cutting-edge angles for different mower blades. Along with this, we will also discuss how to use various tools to get the needed angle.

What Is the Proper Angle To Sharpen the Blades of Lawn Mowers?

The proper angle to sharpen the blades of lawn mowers is 45 degrees to keep it working perfectly. For mulching types of blades, the proper angle for the cutting edge is 35 degrees. Lastly, we have a high lift type of blade where the proper angle is 15 degrees.

Make sure you know what type of blade your specific lawn mower has. There are also several different tools you can choose to sharpen the mower blade.

– Understanding Different Mower Blade Angles

While most modern lawnmowers need their blades to be sharpened at an angle of 45 degrees, exceptions are always present. Three main mower blades are in use these days, and each needs to be sharpened at a particular angle.

• The 45 degrees blade is gaining massive popularity and has become an industry standard. Its steep cutting edge makes it extremely sharp, allowing it to slice through thick grass and bushes. It is also highly durable and produces the minimum airlift, which makes it perfect for mowing grass in sandy lawns.
• The 30 or 35 degrees lawn mower blade is better suited for the mulching type of lawn mower. These have a two to three degrees twist in their blades to create a very strong air suction which helps to direct cut grass clipping towards the mower deck. What’s more, their durability is almost as good as the 45 degrees blade.
• Lastly, some specialized high-lift blades need to be sharpened at a low angle of 15 degrees. They are best used when you want to bag the clippings as the airflow sucks them forcefully into the collecting bag.

– Proper Angle for a Lawn Mower Mulching Blade

A mulching blade needs to be sharpened at 35 degrees proper angle. Unlike regular blades, the purpose of mulching blades is to cut grass into smaller mulch-sized pieces and direct them toward the bag for collection.

With their cutting edge sharpened at an angle of 35 degrees, these blades can cut shorter pieces of grass and produce just the right amount of air suction needed to collect this mulch.

– Importance of the Proper Blade Angle

It is imperative to sharpen mower blades at the correct angle for the grass’s health and efficiency. A blade sharpened at an incorrect angle will tear through the grass or crush it instead of cutting it smoothly. This will ultimately affect the grass’s growth, and it will end up slowing down. The torn grass will spend all of its energy on repairing itself instead of growing further.

You will never get the neat lawn finish you want with the blade sharpened incorrectly. Instead, the lawn will end up looking patchy with an uneven finish. The grass will be cut unevenly throughout the lawn at different heights.

When grass blades are torn apart by the wrong blade, they are at an increased risk of catching infections and diseases. A lawn mowed with such a mower might cause fungal rot to erupt in several patches of the lawn. Grass blade tips might begin to turn brown and wilt away.

– Razor Sharp Angles for Lawn Mowers

It is not recommended to sharpen lawn mower blades to make them razor-sharp to the touch. In layperson’s terms, the blades’ cutting edge should only feel about as sharp as that of a butter knife. The blades are kept at angles of 15, 35, or 45 degrees.

These are the perfect angles to keep the blades sharp enough to cut grass in neat swoops but not sharp enough to cause damage.

– Using a Hand File for the Proper Angle

A hand file is arguably the most common way that DIY blade sharpening is carried out. These are easily available in shops and online for filing metal and plastic.

1. Using a hand file 10 inches long or more is easy to use. It is better to secure this file in a safe for your safety while using it.
2. Try removing the blade from the lawn mower and setting it on a wooden block for support.
3. Hold your hand file at an angle of 45 degrees as exactly as possible unless you use a different blade. Your regular mower blade will likely have a cutting edge of around 45 degrees.
4. Start sharpening from the inner side of the blade to the outer side using firm strokes. This will ensure that the blade stays sharper for much longer than usual.
5. Do not pull and push the file to and from; instead, use unidirectional strokes only. You will know it is beginning to work when the file cuts through the metal.
6. Carry on sharpening until the blade’s cutting edge begins to feel as sharp as that of a butter knife. This is when you know you have done a good job and can stop now.

– Using an Angle Grinder for the Proper Angle

An angle grinder is a better alternative for those who despise spending time and strength manually sharpening through a blade.

Let us warn you, though, that if not controlled properly, you risk overcutting the blade from this tool.

1. Get all your tools, i.e., the angle grinder, a socket wrench, a workbench, and two clamps, and bring them where you will be working.
2. Confirm that the mower is turned off, and then disconnect its spark plug before removing the blade using the socket wrench.
3. Secure the blade on the workbench using both clamps so it won’t move during sharpening.
4. Align the grinding disk along the blade’s cutting edge, which should be around 45 degrees for normal blades and 35 degrees for mulching blades.
5. Using mild to moderate speed, move the grinder from the non-cutting to the cutting side, making repeated strokes.
6. Keep checking in between to make sure you’re going in the right direction and to prevent removing too much of the mower’s substance. Reinstall the blade back in place once you are done and after cleaning off the debris.

– Using a Rotary Tool for Mower Blades

A rotary tool, like an angle grinder, is useful for sharpening lawn mower blades, kitchen knives, gardening shears, etc.

Unlike the hand file, it requires much less physical effort and time.

1. Again, once you have removed the blade from the mower, you must secure it tightly on the workbench using clamps. Otherwise, if the blade moves slightly during work, you risk sharpening it to a much different angle.
2. Set the rotary tool to a minimum speed of about 15 thousand RPM so it can cut through the metal.
3. Align the blade to the cutting edge of the mower at 45 degrees and turn it on. Begin cutting using light to and fro strokes until the butter knife sharpness is achieved.
4. As with most electric equipment, there is always a risk of oversharpening the blade if you are not careful enough. Take as many short breaks as you wish to check if you are going in the right direction.
5. Sharpen both sides equally so there is no imbalance once you are done.
6. After you are done, a rotary tool will create a film of debris on the cut blade. You must wash and clean this off before reattaching the blade to the mower.

– Using a Bench Grinder To Get the Proper Angle

If you or a friend has a bench grinder lying around, then why not put it to work sharpening the mowing blade at a proper angle?

In our experience, this machine works perfectly as a blade sharpener. 

1. Again, you can only use a blade grinder if the blade is removed from the mower first.
2. We recommend using the grinder at a moderate speed for beginners to prevent over-cutting the angle. However, if you already have prior experience with this machine, it’s best to use it at top speed.
3. Place your mower blade on the surface of the grinder at 45 degrees, and then turn the machine on.
4. Keeping the blade flat on the grinder, move it from right to left as it gets sharpened. Holding the blade tightly would help because even slight movement might lead to over or improper cutting. Remember to grind equally on both sides to create a perfect balance.
5. If you feel like this machine needs to sharpen the blade smoothly enough, you can improve it using a file.

– Using a Sharpening Stone To Get the Right Angle

A sharpening stone can be used to sharpen the mower blade while it is still attached to the mower. It depends on your preference whether you want to do this task with the blade attached or removed.

Wear the thickest pair of rubber gloves you have while using the stone to prevent scrapping the skin of your hand. We usually attach the sharpening stone to a drill to make using it more convenient.

Different sharpening stones are available, and you can buy any kind that suits you the most. Ask the store owner to help you pick the right stone to sharpen the blades. After attaching the drill with the stone, turn it on and grind the blade edge at the proper angle, keeping an appropriate measurement.

Even if no drill is available, the stone can be rubbed against the blade’s cutting edge on both sides using manual strength only. It takes longer to get that moderately sharp edge, but it works nonetheless.

– Longevity of Sharp Angles

How long the blades stay sharp at their proper angle depends on how much they are used. The standard agreed upon method is to note how long you use your lawn mower. After using a blade for approximately 25 hours or more, it is time to give it another sharpening. The more regularly you mow your lawn, the more frequently you must carry out blade sharpening.

Frequently Asked Question

– How Can You Tell if the Mower’s Angle Is Sharp Enough?

You can tell if the mower’s angle is sharp enough if it cuts through grass sharply, quickly, and neatly. This is a good sign that they have been sharpened at the right angle. Otherwise, there are certain telltale signs to help you identify a dull blade.

When you mow grass with lawnmower blades that are dull and blunt, the grass will be crushed or torn, and the lawn will assume an unkempt appearance. The edges of the blade might appear visibly frayed or have nicks and dents. This is a clear-cut sign that the blade should be sharpened or replaced.

Conclusion

As our parting message, a summary of this guide on the proper angle to sharpen lawn mower blades is called for.

• The proper angle to sharpen the regular type of blade used in lawnmowers is 45 degrees, whereas for the mulching type, it is 35 degrees.
• Having a proper angle on the blade’s cutting edge is important to cut grass safely and efficiently during lawn care.
• With frequent use, the blade’s cutting edge wears down, and changes also occur to its cutting angle. Frequent sharpening after every 25 hours of use is an important part of mower care.
• You can use many tools to sharpen the blades of lawnmowers, such as the angle grinder, grinding stone, hand file, and bench grinder.

After going through this guide, you now know how important having a proper angle is for lawn mower blades. Make sure to prioritize safety above all else — wear protective clothing like safety goggles and long sleeved shirts when working on blades of any kind. The next time you feel your mower needs to cut more sharply, be confident about sharpening it yourself.