How To Sharpen Lawn Mower Blades With A Bench Grinder: VIDEO GUIDE

Your lawnmower is, without a doubt, one of the most important tools you have at home. It helps you keep the backyard and any other part of your home that has grass looking good. But, with long-term use, the blades could grow blunt, and you might start noticing inefficiency when using the machine. Fortunately, that’s a problem you can solve easily.

In this post, you will learn how to sharpen your lawnmower blades at home using a bench grinder.

What is a bench grinder?

For those of you who are into welding or serious DIYing, you might have come across a bench grinder. It is basically a benchtop machine that drives abrasive wheels for shaping metal or sharpening cutting tools. In this case, we’re interested in the latter function – sharpening cutting tools.

Here Is Video Guide:

Let’s go through the steps for sharpening a lawnmower’s blades with a bench grinder.

Prepare the lawnmower 

Safety note: before you start, consider putting on some gloves and eye protection.

Detach the power

You’re dealing with blades, and the last thing you want is for the lawnmower to start while you’re busy working on it. Therefore, before you disassemble the machine, detach its battery or the outlet, as well as the spark plug.

Don’t know how to detach the spark plug? Look for a prominent wire on the front or the side of the engine and disconnect it from where it is mounted. By detaching this, the engine cannot start.

Access the blades

To reach the blades, you need to turn the mower on its side.

Caution: turning the mower on its side can cause the engine oil to drip into the air filter and the carburetor, causing damage to these parts.

To prevent the engine oil from spilling to the air filter and the carb, turn the lawnmower such that the two parts are facing up instead of down. A box-like plastic case normally houses the two components but if you’re not sure where they’re situated, consult your manual, and if that doesn’t help, call the manufacturer’s support team.

If you don’t want to take the risk of oil spilling into the air filter and the carb, you can try:

  • Running the lawnmower until the gas is finished
  • Draining the oil

Mark the sides of the blade

Here’s a common mistake that folks do: they remove the blade, sharpen it properly, then reinstall it facing upside-down. No matter how well sharpened that blade is, it will not cut the grass. They usually have to go through the process of disassembling the mower to reinstall the blade correctly, which you will not find very convenient.

So, use a marker pen or aerosol paint to mark the sides of the blade. You can just mark the non-cutting side, as the sharpening action will erase the mark if you put it on the side that cuts.

Remove the blade

Most of the time, there’s a bolt at the center of the blade, and it’s quite challenging to remove. Using a ratchet or a wrench might not pull this off as the blade turns with the tool.

First, immobilize the blade by wedging a firm wood block between the mower’s deck and the blade, then use a clamp or vise to unfasten the bolt.

The placement of your blade’s fastener might not be exactly the same as described above, but there’s sure to be a fastener (or fasteners) and depending on its nature and placement, you can use various tools, like wrenches, ratchets, vises, and more to remove it.

Prepare the blade for sharpening

The blade likely has grass clippings and other debris stuck on it; clean that off. If the blade is only slightly dirty, you can use a dry rag for cleaning, but if there’s too much grime, a hose and soap are necessary. If you use water to clean it, be sure to dry the blade completely before sharpening it.

Sharpen it

Precaution: we hope you have your gloves and eye protection on. You don’t want sparks flying into your eyes. Also, be careful when sharpening the tool, keeping your body off the wheel of the bench grinder.

The advantage of using a bench grinder to sharpen the blade is that unlike simple methods like filing, a bench grinder is fast and effective. Again, filing is only good for eliminating tiny dents as opposed to critical sharpening.

The effective approach of sharpening the blade is moving it back and forth against the grinder’s wheel. Be sure to uphold the blade bevel’s original slope to ensure effectiveness and avoid wasting the blade.

Cool the blade

Using a bench grinder to sharpen the blade generates plenty of heat, and as the blade gets hotter, it can grow weak and warp. To protect it from that, cool the blade down several times through the sharpening session.

Have a basin full of water and a few towels nearby. When you sharpen the blade for a few moments, dip it in the water and allow it to cool down a bit before advancing with the sharpening exercise. But before putting it on the grinder, be sure to use the towels to dry it completely.

Alright, that’s all about using a grinder to sharpen the lawnmower blade. Before you go, have a look at the following maintenance tips. They will help you keep your lawnmower blades working efficiently for many years to come, and you will likely be happy with the mowing results every time.

Maintenance Tips

Sharpen the blade regularly. The more you use the lawnmower, the duller the blade gets. That said, consider sharpening the blade at least twice each mowing season; more frequently if you use it very often.

Tip on knowing when to sharpen: of course, you should sharpen when the blade starts getting ineffective. One way of telling the time has come is to observe the grass. If it has a neat, smooth edge, that shows the blade is adequately sharp, but if it looks torn and frayed, the blade has probably grown blunt and needs sharpening.

Balance the blade frequently

When the blade is out of balance, the mower might start vibrating abnormally. One terrible thing about this is that the internal parts might get damaged, and that’s why you need to bring the blade back to balance.

The best time for restoring the blade’s balance is after sharpening. A special piece of equipment known as a balancer and found at hardware stores will come in handy for this task.

Replace the blade

Sharpening may be very helpful for dealing with dullness and minor imperfections like little dents. However, when it comes to major issues like extreme wear and tear, huge cracks, and loss of sturdiness due to many years of use and numerous sharpening times, the best way out is a replacement.

Seek help

Are you in doubt about sharpening the blade? You’re not sure if you’re going to reinstall it correctly? Perhaps you’re worried that the oil will drip into the carb or that the engine will somehow develop an issue.

In case, we’d recommend that you contact a repairer. This might be a good option, and again, by watching what they do closely, you might be able to handle the task next time without needing any help.

The repairman should sharpen the blade, balance it, and reinstall it. They might even apply a rust remover or rust converter to deal with any rust that might be on the blade. Amazingly, they don’t charge much; you might even pay as little as 10 or 15 bucks depending on your location.

Oh, and by the way, rust is another cause of dullness, so you might want to get the perfect rust removers and use them from time to time.

Mower Blades sharpening infographic

Frequently Asked Questions (FAQs)

1. Where can I have my lawnmower blade sharpened?

If you don’t want to DIY using a file or a bench grinder, then you might find help a lawnmower dealer shop that incorporates a service department.

2. How often should I sharpen my lawnmower blade?

It depends on the frequency with which you use the lawnmower, but ideally, during a mowing season, you should sharpen it at least twice. Do it more if you use the mower very frequently.

3. I just purchased new blades for my lawnmower. Do they have to be sharpened before use?

In most cases, new lawnmower blades come pre-sharpened, so there’s no need to sharpen them immediately. Only do so when the blades go dull.

4. Is it possible to sharpen the blade without removing it from the mower?

There are products in the market designed for sharpening the blade without taking it off. The Dremel 675 Sharpener is one such tool but from what we gather, these tools are not very efficient, and they might lead to unbalanced sharpening. However, you can try them and see how they work out for you.

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