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How to Sharpen Lawn Mower Blades

How to Sharpen Lawn Mower Blades

Keeping your lawn mower blades sharp and balanced is important for achieving a quality grass cut. But over time, your mower blade – or blades depending on which mower you have – can and do experience wear. So, maintaining and caring for your mower blade(s) is important both from a safety standpoint and to help provide high-quality mowing performance. 

You’ll want to inspect the blade(s) on your lawn mower periodically, along with the blade adaptor that connects the blade(s) to the mower deck, looking for any bends and cracks, which may happen if you strike a foreign object. If you experience excessive vibration when mowing, then that may be another reason to inspect your mower blade(s).

Both sharpening and replacing mower blades at appropriate intervals are important components of blade maintenance. People ask how often one should sharpen mower blades. To ensure the cutting blade remains level and at the correct angle, you should sharpen the blades on a mower every season, whether they need it or not.

And after repeated sharpening, mower blades will need to be replaced because the repeated grinding can put them outside of the tolerance requirements that were designed to achieve a premium cut. When replacing the blade, be sure to select the OEM-quality blade that’s appropriate for your model. Visit https://www.troybilt.com/en_US/shop-by-part-type/blades to find replacement mower blades for Troy-Bilt mowers. Learn how to replace a walk-behind Troy-Bilt lawn mower blade.

For mowers with twin-bladed decks, such as some riding mowers, blades should have a tip-to-tip contact measurement of within an eighth of an inch from one another. If you notice that cut quality has decreased, then it may be that sharpening has caused the cutting edge to recess. If the cutting edge has been sharpened to the point where it no longer provides clearance within this measurement, then the blades most likely need to be replaced.

Here are some guidelines and step-by-step instructions on how to sharpen lawn mower blades to assist you in caring for the blades on Troy-Bilt walk-behind or riding mowers:

Step 1 – Safety Precautions

Any time you inspect or maintain your mower blade(s), follow all the safety instructions detailed in your mower’s operator’s manual, including protecting your hands with a pair of heavy gloves or using a heavy rag to hold the blade. Allow the engine to run until it is out of fuel before servicing the blade. Do not attempt to pour fuel from the engine.

Disconnect the mower’s spark plug ignition wire according to the instructions specified in the mower’s engine operator’s manual.

Step 2 – How to Remove a Lawn Mower Blade

To remove the cutting blade for sharpening or replacement, follow the instructions detailed in your operator’s manual.

To remove a lawn mower blade on a walk-behind mower, turn the mower onto its side, making sure the air filter and the carburetor are facing up. You may find it helpful to use the Arnold Blade Removal Tool to help make blade removal easy. The clamp mounts to the side of the mower deck, encapsulating the blade and allowing it to hold its position, so you can remove the blade bolt easily.

Remove the center bolt using a socket wrench. You can also use a “cheater bar” for leverage if the blade bolt has become tight. Remove the blade bell support or compression washer that holds the blade and blade adapter to the engine crankshaft.

To change riding mower blades, remove the deck from beneath the tractor. Refer to your mower’s operator’s manual for deck removal instructions. Then, gently flip the deck over to expose its underside.

Place a block of wood between the center deck housing baffle and the cutting blade to act as a stabilizer. Remove the hex flange nut that secures the blade to the spindle assembly.

Step 3 – How to Sharpen Mower Blades

Once the blade is removed, you’ll want to sharpen and balance the blade. You can use a Lawn Mower Blade Sharpener and Blade Balancer Kit to do this step. Simply lock the mower blade into a vice and grind with a file or on a grinding wheel, following the original angle of the grind, and grind each cutting edge equally to keep the blade balanced. You can use the sharpener tool to help you mirror the blade angle as you sharpen it.

After sharpening the blades on your mower, clean the blade to remove any burring. Then, use a blade balancer or a round shaft screwdriver to ensure the blade is level. Remove metal from the heavy side until it balances evenly. An unbalanced blade can cause excessive vibration and may cause damage to the engine and cause the blade to break.

Step 4 – How to Install a Lawn Mower Blade

Once the blade is sharpened and balanced, reinstall the blade on your mower. For Troy-Bilt walk-behind mowers, lubricate the engine crankshaft and inner surface of the blade adapter with light oil. Slide the blade adapter onto the engine crankshaft.

Place the blade on the adapter so the side of the blade marked “Bottom” (or with the part number) faces the ground when the mower is in the operating position. The tips of the blade should be facing up toward the mower deck. Make sure the blade is aligned and seated on the blade adapter flanges.

Place the blade bell support on the blade. Align the notches on the blade bell support with the small holes in the blade, making sure the curve of the blade bell support is going up toward the blade so when the bolt is tightened, it compresses against the blade to keep the blade bolt locked into place.

Replace the hex bolt and tighten the hex bolt to the torque recommended in your mower’s operator’s manual. To ensure safe operation of your mower, periodically check the blade bolt for correct torque.

To install a riding mower blade(s), with the deck removed, gently flip the deck over to expose its underside and line up the hole in the center of the blade with the retainer at the bottom of the deck’s spindle assembly.

Again, use a block of wood to stabilize the blade. Thread on the hex flange nut to secure the blade to the spindle assembly. Use a torque wrench to tighten according to the instructions specified in your mower’s operator’s manual.

Once the blade is reinstalled, you may also want to level the mower deck to ensure the blade is the same distance from the ground on both sides of the mower. Learn more about leveling the mower deck in our Knowledge Center and in a recent Ask Troy Live session on our YouTube channel. You should also consult your mower’s operator’s manual for instructions specific to your lawn mower.