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How Fast Do Lawnmower Blades Spin?

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The weather is warming up outside, which means the time to achieve the perfect yard is upon us. While preparing to tackle the grass that's started growing again, you may wonder how fast lawn mower blades spin. We will explore this along with more helpful information.

Lawnmower blades spin at approximately 3,000 revolutions per minute or RPM at the blade spindle. The blade tip spins at around 200 miles per hour. However, several factors can affect this rate. 

A few variables that can change the speed of lawn mower blades include:

  • The type of lawnmower 
  • Length of blades
  • Blades are actively cutting grass

The average range for lawn mower blade speed is 2,800 - 3,600 RPM for the blade spindle when the blades move freely. This means the blades are not currently cutting grass. The blades' actively cutting can drop the spindle speed down to as low as 2,500 RPM.

The tip of a lawnmower blade usually spins much faster. The range can go from 200 to 250 MPH; however, regulations are in place to prevent blade tips from exceeding 219 MPH. 

Female person gardener mowing green lawn with lawnmower, having problem with broken mower - How Fast Do Lawnmower Blades Spin

Types of Lawn Mowers

Push mowers tend to stay around 3,000 RPM, while riding mowers run slightly higher at 3,200 to 3,600 RPM. Zero-turn mowers remain in the higher range than a riding mower at 3,600 RPM. This means zero-turn mowers have a blade rotating speed higher than other common mowers. 

Another measurement used to show the difference in these mowers is feet per second or FPS. A zero-turn mower has an FPS of 17,000 to 18,500. Other mowers or lawn tractors are usually only 11,000 to 12,ooo FPS. 

Measuring a Lawn Mower's RPM

You may not be sure what RPM your lawnmower has and wonder how you can find out this information. The good news is that you only need one tool. You will use a hand-held instrument known as a tachometer.

Here is a hand-held tachometer. This one tool will be able to measure the RPM of your mower engine and tell you what RPM it runs at.

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Length of Blades

A longer lawn mower blade will spin slower than shorter blades because it will be heavier. It is important to note that a shorter blade that spins a bit faster does not always mean that it will cut better than a longer blade spinning slightly slower. Both will cut the same as long as the blades are sharpened properly.

Red Lawn mower cutting gardening grass process of lawn mowing

How to Make Lawn Mower Blades Spin Faster

If your mower blades are not operating as you want them to, you can make changes to your mower to make the blades spin faster. You can replace the blade pulley with a smaller one and then change out the drive pulley for one that is bigger. However, it is important to note that changing blade spinning speed could potentially be dangerous if done incorrectly or set to too high a speed. 

Because of the potential risks of changing blade speed, improving overall mower speed may be more beneficial. Tips and tricks for achieving this on a riding lawn mower can be found in our post, "How to Make a Riding Mower Mow Faster."

Is it Better to Mow Fast or Slow?

Though you may want to get the chore of cutting the grass over with as quickly as possible, it may be better to take things slowly. The number one reason to cut grass slowly is to ensure a more even cut. If you mow through too fast, you risk tearing your yard rather than cutting, giving it an uneven look. 

Another reason to relax and enjoy the ride is that you risk doing damage to your mower by going too fast. Big clumps of grass from cutting too quickly can get caught underneath the mower. This can create problems and damage various parts of your mower. 

Causes of Mower Running Slowly

Even though going slow while mowing is preferable, sometimes a mower may start running too slow or take a while to start. This could indicate that something is wrong with your mower, and it may be time for some maintenance. 

Here is a small list of a few things you can check on your mower if problems arise.

  • Spark plug
  • Air filter
  • carburetor
  • dirty blades
  • poor quality gasoline

lawnmower at work cutting gardening grass

When to Replace Mower Blades

An important part of keeping up with mower maintenance is keeping up with the mower blades. To get the best cut on your yard, the blades on the mower need to be properly cared for. This means replacing them after a few years when sharpening them no longer seems to be enough or the blades become too thin. 

To learn more about how to do this, check out our post, "What Angle to Sharpen Lawn Mower Blades."

As time goes by, blades are gradually eroded by various debris while mowing any lawn. It is important to check the state of your blades regularly. Sharpening them will help get a good cut on your grass each time, but if you notice the metal starts to look thin, it is time to replace the blades altogether.

Direction to Place Blades

Something to make a note of when you replace the mower blades is the direction in which the blades spin when the mower is on.

The direction the rotation of the blades moves in is where the blade's cutting edge will need to be pointed. If the rotation turns to the right, the blades sharp side should be pointed to the right. 

Making sure the sharp side of the blade is pointing in the same direction it will rotate in ensures the blades can do their job and cut your grass.

How Tight Lawn Mower Blades Should Be

 Female person gardener mowing green lawn with lawnmower, having problem with broken mower

Most lawn mower manuals will have an exact measurement guide for how tight the blades need to be. However, the general rule to follow is making sure the blades do not spin freely on their own.

If this happens, they are far too loose and can be dangerous. If the blades are not tight enough, they can fly off after starting the mower.

Blades that are too tight also pose a threat. You will want to make sure that you can manually spin the blades with your hand without much difficulty.

If you cannot make them spin after using a little bit of pressure, they may be too tight. Trying to run the mower with blades too tightly fastened could cause damage to the blades and mower.

Mower Blades Aren't Turning

You may notice the blades on your mower are no longer turning when they should be. This suggests you could have an issue with a different part of the mower. The part of the mower that houses the blades is the deck.

 This deck has a belt that spins the blades of the mower. If this belt is worn down, it will have trouble making the blades move. Replacing the deck belt in your mower is the most likely cause for blades that no longer rotate.

lawn mower blade close up

How Lawn Mower Blades Spin

With all this talk about mower blades, you may be curious to learn more about how they work. Modern mowers operate much differently than mowers of the past.

Over a century ago, most lawn mowers were reel mowers. These mowers only ever got power from people pushing them through the yard. The blades on these mowers were essentially scissors fastened underneath the mower.

Today, lawnmowers are predominantly gasoline or electric, rotary mowers. They no longer rely on the person pushing them to get power. This opened up new possibilities for how to move the blades.

Rotary mowers have blades that rotate, or spin, around to slice at the grass rather than snip it like previous mowers. These mowers most often require gasoline to run, but some have cords, batteries or are solar-powered.

Summary

Today's most lawn mowers are rotary mowers that work by using fuel to start the engine and rotate the blades doing the cutting. These engines are typically in a range of 2,800 - 3,600 RPMs or revolutions per minute. This translates to a blade spin speed of around 200 mph. 

Although it is possible to increase blade speed yourself, most will still be within this range due to guidelines that keep blade speed below 219 mph. 

The blade speed is also affected by mower type, blade length and condition, and actively cutting grass. They may stop spinning altogether if the deck belt of the mower needs to be replaced.

You will need to replace the blades when you notice them thinning out. It is crucial to ensure that they are correctly tightened back to the mower as being too loose or too tight can be dangerous. 

With all this information on lawnmowers and blade care, we hope this grass-cutting season will be a good one!