Can I sharpen mower blades with angle grinder?

Quick Answer

Yes, you can sharpen mower blades with an angle grinder. An angle grinder is actually one of the best tools to use for sharpening dull mower blades. The high speed and abrasive grinding discs of an angle grinder make quick work of removing nicks and reshaping the cutting edges of the blades. With the right technique, an angle grinder can restore a sharp edge to mower blades so they cut cleanly again.

Steps to Sharpen Mower Blades with Angle Grinder

Here are the basic steps for sharpening mower blades with an angle grinder:

1. Remove the mower blade from the mower deck.
2. Clean the blade to remove all grass clippings and debris.
3. Clamp the blade securely in a vise or use a pair of pliers or clamps to grip the blade.
4. Inspect the blade to locate the cutting edges and assess the wear and damage.
5. Use a thick grinding disc on the angle grinder to reshape and sharpen the cutting edges.
6. Cool the blade by dipping it in water to prevent overheating.
7. Make balanced passes along both sides of each cutting edge.
8. Carefully hone and polish the cutting edges when sharp.
9. Test the balance of the blade before reinstalling it.

Follow those basic steps while observing proper safety practices for using an angle grinder. Wear eye protection, leather gloves, long sleeves and close-toed shoes. Work slowly and carefully to get the cutting edges of the mower blades back into shape.

Why Use an Angle Grinder to Sharpen Blades?

An angle grinder is an excellent choice for sharpening dull mower blades for a few key reasons:

• Power – Angle grinders have very high rpm motors that quickly and efficiently cut, grind and shape metal.
• Speed – The fast spinning discs rapidly reshape and hone the blade edges.
• Control – The compact size makes it easy to handle the grinder and sharpen each section of the blades.
• Versatility – Grinding discs come in many grits and materials to handle rough grinding or fine polishing.
• Convenience – Most DIYers already own an angle grinder making it a handy sharpening tool.

Compared to using a file or bench grinder, an angle grinder with the right discs can reshape and sharpen a mower blade much faster with greater control and precision. The ability to quickly switch grinding discs and sharpen at any angle makes an angle grinder the ideal tool for maintaining a quality cutting edge on mower blades.

Angle Grinder Sharpening Technique

Here are some key technique tips to follow when using an angle grinder to sharpen mower blades:

• Start with a thick, coarse grit disc like 36 or 60 grit to aggressively grind and reshape the cutting edges.
• Position the blade so the area you are grinding is flat against the spinning disc.
• Use even, consistent pressure and sweeping motions along the edge.
• Grind both sides of the blade to keep the edges balanced.
• Cool the blade frequently by dipping in water to prevent losing the temper.
• Switch to a finer 80 or 120 grit disc to refine and hone the edges.
• Finish polishing with a very fine 150+ grit disc for a razor sharp edge.
• Maintain the factory bevel angle as you sharpen the edge.
• Make sure each cutting edge receives an equal number of passes.

The key is using the coarse discs to reshape the edge, then finer grits to hone and polish it. Take your time and periodically check your progress. Compare the ground sections to unworn sections to judge when the edge is sharp enough. Cooling the blade prevents overheating that can ruin the tempering of the blade.

Safety Tips

Sharpening blades with an angle grinder can be dangerous if proper precautions are not taken. Here are some key safety tips:

• Wear eye protection to shield your eyes from flying sparks and debris.
• Use thick leather gloves to protect your hands from the spinning disc.
• Wear a long sleeve shirt, pants and close-toed shoes for protection.
• Keep your grinder hand positioned away from the disc rotation to avoid back torque if the disc binds.
• Take care not to overheat the blade which can ruin the tempering.
• Use clamps or pliers to grip the blade instead of holding it with your hands.
• Unplug the grinder when inspecting or adjusting the blade.
• Avoid awkward hand positions that make controlling the grinder difficult.

Also be sure to set up your work area to protect yourself and surfaces from sparks. Never cut or grind on a blade while it is still attached to the mower. Stay alert and work slowly and carefully for maximum safety.

Do’s and Don’ts

Here are some good practices to follow and mistakes to avoid when using an angle grinder to sharpen mower blades:

Do:

• Inspect blades before sharpening and replace severely damaged ones
• Use the proper size grinder disc for the blade you are sharpening
• Clamp the blade securely in a vise or with pliers/clamps
• Maintain the factory bevel angle when sharpening
• Grind both sides of the blade evenly
• Dip the blade in water regularly when grinding to cool
• Start with a coarse grit disc and progress to finer grits
• Compare ground sections to unworn sections
• Hone and polish the edges using the finest grit disc last
• Balance and inspect the blades before reinstalling

Don’t:

• Hold the blade by hand while grinding
• Grind so much that you overheat and ruin the blade temper
• Touch the grinding disc when it is spinning
• Twist or bend the disc when grinding as this can cause it to shatter
• Force the grinder when grinding – use smooth, even pressure
• Grind on the back side or sides of the blade
• Reinstall unbalanced, damaged, or poorly sharpened blades

Following the proper do’s and avoiding the don’ts will help you consistently sharpen your mower blades safely and effectively. This will save you money on replacements and repairs. Taking the time to properly maintain your mower blades using an angle grinder will maximize your mower’s performance and cutting efficiency.

Choosing the Right Grinding Discs

Having the right grinding and cutting discs for your angle grinder is critical to get the best results sharpening blades. Here are some tips on choosing discs:

• Use reinforced fiber or fabric discs which resist shattering from grinding torque.
• Choose various grits from coarse (36 grit) to fine (120+ grit) for shaping and polishing.
• Discs specifically for metal grinding provide faster cutting action.
• Thicker discs resist warping and allow more pressure for faster grinding.
• 4-1/2″ to 5″ diameter discs fit most small angle grinders used for DIY jobs.
• High quality brand name fiber discs like 3M and Norton remove material faster and last longer.
• Avoid cheap no-name discs which shatter easily from grinding forces.

The right combination of fiber grinding discs for your angle grinder makes it much easier to accurately and efficiently sharpen lawn mower blades. Having an assortment of grits allows you to be more aggressive with reshaping or more delicate when polishing the edge. Check the recommending grinding discs for your grinder model.

When to Have Blades Professionally Sharpened

While sharpening mower blades yourself with an angle grinder is fairly straightforward, there are some cases where you may want to have them professionally sharpened instead.

• If the blade is severely damaged, warped, or the cutting edges are gouged deep it may need professional equipment to properly recondition it.
• For a more precise, razor-like edge, the specialized equipment at a shop may provide better results.
• If you need to sharpen the blades frequently, the cost of professional sharpening may end up being cheaper long-term than purchasing all the grinding supplies.
• Professionals can ensure the blades are balanced after sharpening reducing vibration and mower wear.
• Shops have specialty grinding jigs to hold, position, and cool the blades.
• You can drop blades off at a shop saving you time and effort.

Evaluate the condition of your mower blades to determine if you can successfully sharpen them yourself or if it would be better to let professionals handle it. For basic maintenance sharpening 1-2 times per year, doing it yourself with an angle grinder is usually the cheaper and faster option.

How Often to Sharpen Mower Blades

Here are some guidelines on how often you should sharpen your mower blades:

• At least once per year – even blades used in normal lawn conditions will gradually dull over a season of mowing.
• Every 25-50 hours of mowing time – frequent mowing on thick or dirty grass will wear blades faster.
• When lawn cutting performance declines – faded quality of cut is an indicator of dull blades.
• After striking hard objects like rocks, sprinkler heads, etc – impacts will nick and deform the cutting edges.
• When excessive vibration occurs – imbalance from blade wear will cause vibration.
• At the end of the mowing season – sharpening before storage will prevent rusting over winter.

Make it a habit to inspect your mower blades periodically and sharpen them at the first sign of wear and diminished cutting performance. Letting blades get too dull before sharpening makes the job harder and can lead to an uneven cut quality. Stay on top of your mower blade maintenance.

Signs Your Blades Needs Sharpening

Watch for these signs that indicate it is time to sharpen your mower blades:

• Reduced cut quality – ragged, uneven or faded appearance.
• Increased grass clumping – blades unable to mulch as cleanly.
• Excessive vibration – imbalance as blades wear unevenly.
• Decline in cutting power – engine strains more mowing.
• More uncut grass – blades not cutting cleanly across the full width.
• Higher fuel usage – engine working harder with dull blades.
• Overheating engine – engine taxed from lack of blade speed.
• Blade nicks and dings – deformities along cutting edge.

Don’t continue trying to mow with damaged, worn, or dull blades. The decline in cut quality and engine strain will just get worse. Take the time to periodically inspect your blades and sharpen them at the first signs of wear. It’s cheaper and better for your mower than trying to delay blade maintenance until absolutely necessary. Catching dull blades early also makes sharpening much quicker and easier.

How to Balance Lawn Mower Blades

Balanced mower blades are essential for smooth cutting performance and reduced vibration. Here is how to balance blades:

1. Clean the blade to remove any dried grass or debris.
2. Locate the center mounting hole on the blade.
3. Insert a nail into the center hole and rest the blade on a steady surface.
4. Give the ends of the blade a spin – a balanced blade will remain steady.
5. If either end drops, that end is heavier. File or grind that end until balanced.
6. Repeat the process until blade remains steady when spun.
7. Use a blade balancing tool for greater accuracy.

Ideally, check the balance prior to sharpening and after to ensure grinding has not disrupted the original balance. Take time to balance your blades properly for best performance and safety.

Can I Use an Impact Wrench to Remove Blades?

It is not generally recommended to use an impact wrench when removing or installing lawn mower blades. Here’s why:

• Over tightening – Impacts apply tremendous torque and can over-tighten the mounting bolt.
• Damage – Excessive torque stresses and damages the crankshaft splines.
• Rounding bolts – High torque rounds off the mounting bolt head.
• No precision – Impacts do not allow a controlled torque for proper tightness.
• No adjustment after – No way to check or adjust tightness after impacting.

It is safer and better to use hand tools like a socket wrench, extension bar, and bench block to remove and install mower blades. This allows precision tightening to the manufacturer’s torque specs without risk of damage. Only use an impact for initial crack off of seized bolts.

Conclusion

Sharpening your lawn mower blades regularly with an angle grinder is an easy and effective way to maintain a quality cut. Follow proper sharpening techniques and safety precautions. Check for signs your blades need sharpening and don’t wait until they are completely dull. Balanced, sharp blades will maximize the performance of your mower, reduce strain on the engine, and provide a clean, even cut quality. Sharpen often to get the most out of your mower blades.