Can a Lawn Mower Blade Fly Off?

You’ve probably run over a few foreign objects with your lawn mower before, but can a lawn mower blade really fly off just like that? Nowadays you can read all kinds of stories online, so it can be hard to tell myth from reality. So, what’s the truth?

Can a lawn mower blade fly off? A lawn mower blade can fly off if the blade or blade adapter is damaged. A loud rattling sound or excessive vibrations are signs that the blade is not functioning correctly. If you notice either of these problems, turn off the motor and have the machine serviced immediately.

Late spring is usually the time that you dust off your lawn mower for the first mowing of the season. Although some people, often those with large lawns, dread the thought of another long summer of yard work, other homeowners look forward to the warm weather and neatly manicured lawns. Whichever type of person you are, you’ve likely seen your fair share of lawn mower mishaps or malfunctions. 

For a machine that seems so simple, the lawn mower frustrates more homeowners and landscapers than any other tool. To avoid any potential hazardous outcomes, you should examine your yard for obstacles before mowing, regularly clean your mower, listen for new rattling noises or vibrations, and avoid trying to repair the mower if you’re unsure what the problem is.

How Can a Lawn Mower Blade Fly Off?

There are plenty of forums and videos online that focus on lawn mower problems. It’s evident that mower manufacturers, even the ones with exceptional reputations, have not produced a maintenance-free machine so far. 

The top of the line mowers should be more reliable than cheaper models, but even the priciest machine can disappoint you after a few seasons. Usually, this is not the fault of the manufacturer but is the result of the failure to maintain the mower properly. The following is a list of possible reasons your lawn mower blade can fly off. 

  • Manufacturer defect
  • Loose blade bolt
  • Sheared blade adapter studs
  • Incorrect replacement parts
  • Damaged blade
  • Dull Blade
  • Grass and debris buildup

Now, let me give you some more details on these.

Manufacturer Defect

Although it’s rare, some lawn mower accidents are the result of defective equipment. If you purchase a new mower and you notice a strange sound or intense vibration, turn off the mower right away. Don’t attempt to repair a new mower. 

Limited warranties become void if you tamper with the mower and damage it further. Any defect is the responsibility of the company, and you will not have to pay for the repairs. In 2016, an Australian Company recalled their mowers when they discovered a minor defect could potentially cause the mower blade to fly off.

The faulty mowers were missing an anti-vibration washer in the blade disk, and the recall repairs only consisted of adding the washer to the blade adapter.

Loose Blade Bolt

The lawn mower blade is attached to the blade adaptor with a bolt, and the bolt must be tightly fastened to the blade for the mower to cut correctly. If the bolt becomes loose, the blade will become unbalanced and can eventually break the bolt and fall off.

Before mowing your first lawn of the season, you should check your blade to make sure it is securely attached to the blade adapter. Also, if the mower starts to vibrate uncontrollably sometime in the mowing season, check the bolt first before attempting repairs.

If you had your mower shipped to your home from an online retailer, check all of the screws and bolts for tightness. Sometimes, the shipping process can loosen screws and nuts on pre-assembled machines.

If you aren’t sure just how tight your lawn mower’s blade should be, check out this article I wrote about this topic. 

Sheared Adapter Studs

Your lawn mower’s blade attaches to the blade adapter with a long bolt. The other end of the adapter attaches to the engine’s crankshaft, and when you start up the mower, the crankshaft spins the adapter connected to the blade. 

The adapter has two metal studs that fit the two holes in the blade. When you run over something solid like a rock or piece of metal, the blade, and the adapter can become damaged. If the metal studs are damaged when a foreign object is hit, the blade will not fit securely onto the adapter. 

Since the studs are machined into the adapter, the entire adapter must be replaced to operate the lawn mower safely. If you notice that your blade continues to fall off after it’s been replaced, the adapter is likely the culprit.

Incorrect Replacement Parts

Most replacement parts, like the blade, are similar among different manufacturers. However, some parts, especially those sold outside of the United States, are produced with metrics rather than standard specifications.

If you order a part online for your lawn mower, you must ensure that it is a standard part. Metric and standard parts will not work together, and if you place a metric adapter on your mower with a standard bolt and blade, the blade can fly off. 

In the following video, a man displays how a metric adapter fits loosely on the lawn mover he’s repairing:

A standard adapter should fit tightly on the bottom of the mower, but the loose-fitting metric piece caused his client’s blade to fall off the mower.

Damaged Blade

The most common reason for a blade to fly off a mower is prior damage to the blade. Rocks, large hardwood branches, and other foreign objects can permanently damage your mower. The blade can develop chips and cracks from hitting hard objects that will only get worse with time.

The blade spins at an incredibly high RPM, and if it’s cracked, a piece can break off and fly off of the mower. When you hear a loud crash associated with your blade hitting a hard object, stop the mower and inspect the blade. If the metal is bent or cracked, replace it before you use the mower again. Most blades are inexpensive and easy to replace.

Dull Blade

A dull blade is not as hazardous as a damaged one, but it can become dislodged easier than a sharp blade. A sharp blade can cut through some foreign objects, but a dull blade will only butt against the object and ricochet. If you repeatedly hit objects with a dull blade, it can become dislodged.

If you notice that your grass has small tears after being mowed instead of a clean-cut, you should sharpen the blade or replace it. Use protective gloves to handle the blade before removing it. Although the blade is dull on one side, the other side can cut your hands if you’re not careful.

Grass and Debris Buildup

If you look underneath your mower, you’ll probably see a fair amount of grass and dirt near the blade. Over time, the debris can build up and eventually interfere with the blade’s spinning movement. The blade can become damaged by striking the debris and can subsequently fly off.

To avoid this scenario, you should regularly clean the mower’s undercarriage. Some models include an attachment on the front of the mower that connects to a water hose. When you turn the hose on, the water sprays the undercarriage and removes the grass and debris.

How Can You Prevent Your Lawn Mower Blade From Flying off?

A flying lawn mower blade is a scary thought, and thankfully it’s not a common occurrence for people who maintain their mowers correctly. Keeping your lawn mower clean and keeping the blade sharp will go a long way to ensuring the mower will function safely. 

Clean the Mower

After each mowing, use a leaf blower to clean off the excess dirt and grass. Tilt the lawn mower back and spray water under the mower to remove the built-up grass and dirt. Use the cleaning spout if your lawn mower has one. 

When you tilt the mower, make sure that the air filter is pointing up. If you tilt the mower towards the air filter, the gas can enter the filter and ruin it.

Inspect Your Yard Before Mowing

Before starting your mower, walk around the yard, and inspect it for large rocks, sticks, and children’s toys. By removing any possible obstacles, you decrease the likelihood that your blade will become damaged.

Inspect Your Mower for Loose Bolts or Screws

If you notice an annoying rattling sound when you start the mower, the problem might be something simple like a loose bolt. Inspect your mower frequently and tighten any loose bolts or screws.

Keep the Blade Sharp

With a large yard that you mow every weekend, you should probably sharpen the blade two or three times a season. A sharp blade will not produce ragged tears and is better for your mower and your lawn. 

Torn grass from a dull blade can leave the grass vulnerable to infections. Infected grass will quickly turn brown and can ruin the lawn’s appearance if left untreated.

Closing Remarks

Keeping your lawn mower clean and well-maintained will minimize the likelihood of a blade malfunction. Although a flying blade scenario is rare, a mower’s sharp blade can cause substantial damage if it’s dislodged. 

Now, lace up your steel-toed boots and fire up the lawn mower!



Peter Toth

Hi! I'm Peter, the owner of BackyardGadget. Working around the house has always been a big part of my life. I've created this site to share my experience, and to help people choose the right tools for the job. Thank you for stopping by!

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