Learn The Best Way To Sharpen Lawn Mower Blades

For a lawn mower to have sharp blades is synonymously necessary as for the trees to bear fruits and the sun to shine! A matter of absolute necessity; otherwise the very purpose of its existence is defeated.

The blades of a lawn mower cut your grassy lawn in a faster and neater manner. 

Hence, it is absolutely necessary for the blades to be sharp, in a knife-like manner so that they cut the grass neatly, precisely and fast without scalping the grass from the roots. 

It becomes all the more important for the mower to have sharp blades if you’ll be operating the mower on hills as there can be uneven terrains and grass needs to be cut at all heights.

After a period of regular usage, the blades of the mower become blunt and you have to pay attention to lawnmower blade sharpening. If the blades are not sharp, they’ll keep cutting the grass very poorly and can eventually break, not letting the lawn mower run. 

So if you observe uneven patterns, clumps of grass or scalped off grass in your lawn after a mowing session, it is time to sharpen mower blades and check if they’re installed correctly. 

In this article, I have brought a comprehensive guide about how to sharpen lawn mower blades and the correct way to re-install them after you’ve sharpened them. 

Step-By-Step Tutorial For Lawn Mower Blade Sharpening

Before you proceed to sharpen the lawn mower blades, gather the tools and materials mentioned below. 

Required Tools	Required materials
A FileRagsA set of Sockets/RatchetA Vise	Gloves for protecting hands Protective eye maskWear long sleevesA WD-40 lubricant oil/spray

The procedure of lawn mower blade sharpening has three main steps-

1. Removing the blades, 
2. Sharpening them and then, 
3. Re-installing them back in the correct manner. 

Follow through each step meticulously. Skipping any step can lead to adverse consequences on the mower’s blades. 

Step 1: How To Remove The Lawn Mower Blades

1. To start with, you first need to remove the blade from the mower that needs sharpening. Before you start, disconnect the spark plug or the power source from the mower. This is very important to protect you from any accidental power hiccups. 
2. Wear your guarding eyewear and gloves to be safe.
3. Now, start turning the mower to its side, with the carburetor and the air filters upside. 
4. Use a marker to identify the blade’s bottom side. This will prove handy later on while installing the sharpened blade with the right-side up.
5. Now, locate the bolts that are securing the blade to the shaft. Pick up the socket and the ratchet to make the bolts loose till the blades are released. 
6. If you find it difficult to get hold of the bolts, support the blade with a 2×4 wooden piece for clamping the blade. Now, grab and loosen the bolt.
7. In case, the bolts and the blades’ shafts are jammed together, use WD-lubricant oil and let it sit on them for 2-3 hours. Then, remove the blade. 
8. Use a dry clean cloth or a rag to wipe the blade clean. 

Note: At times, the blade might be oddly greased and dirty. In that case too, use the above suggested lubricant oil on the blade. Let it sit on the grease, dilute it before you wipe the blade clean. 

Step 2: How To Sharpen Lawn Mower Blades

The blades of a mower have an edge of about 3-4 inches on the opposite side. Inspect these sides to determine if the blade is just dull or is damaged. 

• If the blade has any cracks or is completely bent, replace it. Don’t attempt to sharpen a damaged blade. However, if the blade is just dull or chipped off, then you must sharpen it. 
• Your goal is to achieve gentle sharpness on the blades with polished sides. Sharpen the mower blade like a butter knife, not a razor-sharp knife. 
• Extremely sharp blades dull out fast and can also cut your finger. They also need to be sharpened constantly which is an exhaustive task. 

Now that you have the dull blade with you, let’s proceed to sharpen the lawn mower blade. Here, I have demonstrated three different methods. 

1. Sharpen mower blades using metallic file and clamp;
2. Using a grinder;
3. Using a blade sharpening stone. 

Study all of these and then decide which one for you, is the best way to sharpen lawn mower blades. 

Pro Tip: Make sure, you’re wearing long sleeves and the protective gear ( the gloves and the eyemask) before you start to work with blades and grinders. 

Mechanism 1 : Using A Clamp and File

1. Put on the protective gear to shield yourself from the sparks and metal leftovers.
2. Use a file of about 10-inches or a grindstone at a 45° angle for sharpening the blades’ edges and secure the blade in a vise. 
3. For sharpening, move the file in a perpendicular direction to the edge of the blade.
4. Keep pushing the file only in one direction, not in forward-backward direction.
5. While you’re filing the blade, you should be feeling the teeth of the file on the blade. If you cannot, pressure the file a bit more. 
6. Keep following the angle on the blade edge and smoothen out the rough edges. 
7. Ideally, you should be able to sharpen the mower blade within some 50 filing strokes.
8. After you’re finished filing one edge of the blade, let the vise release it.
9. Now, switch over to the other edge and repeat the process. 

You need to carefully handle the file at the correct angle.This is a slow but easy method to sharpen the lawn lawn mower blade, and definitely works. 

Now, let’s move on to the next method and learn how to sharpen lawn mower blades on a bench grinder. 

Mechanism 2: Using A Grinder

This method is the fastest method to sharpen the blades. 

1. Put on the earplugs and rest of the protective gears for shielding yourself from sparks and the loud noise of grinding
2. Clamp the blade securely using a vise. Out of an angle grinder and a bench grinder, I prefer the angle grinder for the portability and the liberty to move the grinder as per the edges. 
3. Now, begin aligning the grinder blade to the cutting edge of the dull blade. 
4. Start moving the grinder against the blade’s edge in the forward-backward direction.
5. Keep following the angle of the blade’s edge, sharpening the blunt spots on the blade.
6. This way, sharpen one edge of the blade. Now, repeat the same process on the other edge of the blade.
7. Using a grinder is also the best way to fix a severely damaged blade with rough gouges which cannot be smoothened using a hand file.

Mechanism 3: Using A Drill And Blade Sharpener 

1. This is another method of sharpening the mower’s blades by using a drill and blade sharpening kit.
2. Start by clamping the blade into the vise and inserting a blade sharpener into the drill. The blade sharpener would have a circular grinding stone with an inclined edge, a guide piece and ¼ inch shank.
3. After pulling the drill’s trigger to power it up, keep the grinder over the blade’s edge. In this position, the flat guide of the grinder should be against the rear side of the blade and the blade’s cutting edge should be slotting into the bevel. Maintaining this position will keep the blade accurately inclined at the right angle. 
4. Now, with medium pressure, keep moving the stone backward-forward alongside the blade’s edge. 
5. After you have stroked the blade for 4-5 times, check the blade’s edge. It should be butter-knife-like sharp and should not have chipped edges. 
6. After you’re done sharpening one edge of the blade, follow the same process on the other side of the blade. 

Out of all the three methods, using a grinder is the best way to sharpen lawn mower blades since it is the fastest method. 

Is The Blade Sharp Enough Now? Test it- 

Now that you have sharpened the lawn mower blades, let’s test it. 

• Pick up a piece of paper or a blade of grass. 
• When pulled over the blade, if it is cut easily, the blades are sharpened. 

If you own a riding mower and are wondering how to sharpen riding mower blades, feel free to use the above methods as they can be used on both the push mowers and the riding mowers. 

This step-by-step tutorial given above will help you use your lawn mowers to the best of their capacity, giving the neatest and healthiest cut. 

Tip : In case you’re going to sharpen the mower blades using a powered sharpener, please refrain from overheating the blade’s edges. Test by touching it and If it feels too hot, then it’s actually hot which it should not be. To cool the blades down, dip them in a bucket of cold water. 

Step 3: Balance The Blade Correctly

Now since the blades are sharpened, we must check the balance before installing it back. When you sharpen the mower blades, the metal composition on either of the edges can become less or more which imbalances the blades. 

Using imbalanced blades on the mower, even if they’re sharp enough, can just be the start of a series of lawn mower issues like steering problems on Husqvarna, sudden stalling of an Ariens mower in between a mowing session, Simplicity mower’s excessive vibration etc. 

Hence, to avoid such problems, you must ensure that the blades are correctly balanced. The blade should not be wobbling on the mower else the mower will keep vibrating and several mower deck problems can arise. 

Use these steps to check the blades’ balance on your mower:

• Supporting the blade at the centre, insert the tip of a screwdriver through the blade hole. The blade should be balanced on the screwdriver’s tip. 
• Now, clasp the blade in a horizontal position and then, release. It should remain leveled.  
• If you notice the blade dropping in either direction, then the blade is not balanced. 
• The side of the blade which is dropping, is the heavy side. Shapren the heavy side with a few more grinding strokes to reduce the metal composition. 
• After that, test again using the steps given above. 

Give the blade a few strokes till both the sides end up balancing well. Only then you can proceed to use the last leg of this guide which is re-installing the blades back on the mower. 

Step 4: How To Install the Blade After Sharpening It

After you have sharpened the blades and balanced them correctly, it’s time to re-install them back on the mower.

Use these steps to attach the blades on the mower again:

1. Before you reinstate the sharpened blade, clean the area and remove any accumulated debris, sticky or dried out mud or grass clippings. You can also use a wired brush or a knife used for putty.
2. Look for the mark you made on your blade in the beginning. That was the blade’s bottom side. 
3. Now, while inserting the blade back on the bolts, check that the marked side faces you.
4. Once the blade is inserted, tighten it using a socket wrench. Check that it’s very tightly secured for the mower to run properly.
5. Now, connect the spark plug and check the fuel tank. 
6. Start the mower now and see if it starts smoothly. 

So, this was all about lawn mower blades sharpening starting from the scratch- removing the blade, sharpening it and then, reattaching it. 

Use any method you prefer but follow that in a meticulous manner and you would be able to sharpen the blades easily without any hassle.

Useful Tips For Maintaining The Lawn Mower’s Blades

After you’ve learnt the correct technique to sharpen the blades, you must master the blades’ maintenance techniques so that the blades stay sharp for a long time and their longevity is ensured. 

• Clean the blades after each mowing session.
• Avoid mowing a wet lawn, at all costs. Wait for the grass to dry out completely.
• Keep the blades’ shafts and the bearings free of any accumulated debris.
• Ideally, you should be sharpening the blades after 20-25 hours of usage. 
• Determine the time you take to mow your lawn. Then, multiply that time to the no. of times you mow the lawn each week. That’s the time you should sharpen the lawn mower blades. 
• Change the blades if they’re broken. Do not use broken blades on your lawn. 
• Lastly, always keep a spare blade for your mower, for emergencies. 

FAQs

Q1. Is it better to sharpen lawn mower blade or replace them?

Answer – You must sharpen the blades regularly to avoid uneven patterns of cutting and to ensure longevity of the blades but you must only replace them if they’re broken. In that case, they can neither be sharpened or repaired. 

Q2. How do I know it’s time for lawn mower blade sharpening?

Answer – You would know it’s time to sharpen lawn mower blade if the grass in your lawn starts showing white or brown tips after you mowed it recently. If the blades are completely dull, they won’t cut the grass at all. Also, due to dull blades, the engine starts performing very sluggishly and it starts taking very long to mow the lawn. 

Q3. Do you need to sharpen only one or both sides of the lawn mower blades?

Answer – The blades of a lawn mower must be sharp only on one side, the way a knife is sharp. Hence, ensure that you sharpen only the chiselled side of the mower’s blades. 

Q4. My lawn mower is new but the blades are not sharp. Why?

Answer – Mostly, the new lawn mower has sufficiently sharp blades but if they have become dull very quickly, check your yard for small stones, rocks and debris which can cause the blades to become dull and wear out faster than usual. 

Q5. Can the blades become dull due to mowing a wet lawn?

Answer – Definitely, yes! Wet chunks of grass can not only dull the blades but also corrode them in the long run, if they’re not cleaned. Not only this, wet grass can clog the blades, the deck and result in poor and sluggish performance of the engine. The mower’s engine can also bear various issues such as steering problems if the debris clogged around the blades is not cleaned regularly. 

Conclusion 

If you continue using dull blades to mow your lawn, the grass can start browning and withering ultimately. Dull or blunt blades not only leave your lawn uncut and untidy, but also can cause serious damage to the lawn soil. 

The best time to cut the lawn grass is between 2:00 pm- 4:00 pm as mowing the lawn during midday harsh sun can damage the feeble grassy leaves and cease their growth. So, it’s always best to mow your lawn in the late afternoons and water the lawn right after a mowing session to help the cut grass heal. If the grass in your lawn starts turning yellow after a mowing session, then supply sufficient water to the grass and let the grass grow properly before cutting it. 

So with all these grass-maintenance tips and cutting it with sharp blades, you’re sure to enjoy neat streaks in your lawn with the grass looking greener and healthier than ever.