Should Lawnmower Blades Be Razor Sharp? (Solved & Explained!)

Cutting your lawn is an essential part of your garden maintenance routine but you don’t want your lawnmower blades to be too razor-sharp as this can affect their lifespan. You need a blade that can cut the grass cleanly and to achieve this you want to be able to touch the blades with your hand without them cutting you.

In this article, we explore how to maintain your lawnmower blades to ensure they are cutting effectively and to keep them that way for as long as possible. 

How sharp should my lawnmower blades be?

As a rule, your lawnmower blades should stay the same sharpness as the day you bought it as they are manufactured to the best specification for the model. You will find that most blades maintain a sharpness angle of between 30 and 40 degrees, this ensures it will cut through weeds and grass with ease and won’t be too severely affected by stones and rocks. 

Any blades sharpened to an angle of 30 degrees or less will find that the blade is too thin and could fracture when colliding with rougher terrain. 

Will a sharp blade make a difference to my lawn?

Of course! A sharp blade will trim the grass neatly, ensuring that your lawn isn’t rugged and rough, and doesn’t cause the grass to dry out. You will find that grass that is torn rather than cut will fray at the edges, and these will brown and discolor over time which can make your lawn look unsightly. 

How do I sharpen my blades?

You should always check your blades before mowing your lawn, doing a thorough check in the Spring when you know you are likely to start using it more regularly. Inspect the blades for any nicks, bends, or dents so you can gain an understanding of where you need to work on. The following are the steps you then need to take to sharpen your blades:

  • Prepare Your Tools: For this task you will need a grinder, rags, a vice, a ratchet set, and a lubricant such as WD-40.
  • Wear Protection: Ensure you are keeping yourself safe by wearing safety goggles, heavy-duty gloves that are resistant to cuts, and an apron to shield your body and clothing. 
  • Check the Spark Plug is Disengaged: The spark plug will need to be disengaged as this protects against the machine trying to start on its own. 
  • Remove the Nicks and Dents: Secure your blade into the vice and use a good grinder to remove any dents or nicks. 
  • Sharpen in One Direction: You want to sharpen your blades in one direction, maintaining a bevelling angle of at least 40 degrees and ensuring it is no less than 30 degrees. 

Balance your Blades: Test the balance of your blades after sharpening them as this is equally as important as their sharpness as it will ensure your blade lifespan is maximized. 

How frequently should I sharpen my blades?

Genuine tempered blades should last you at least a year, and most experts agree that you wouldn’t want to sharpen your blades more than four times a year. The more frequently you sharpen your blades, the more likely you are to have to replace them at regular intervals.

As a rule of thumb, you should be able to keep your blades mowing your lawn for around 1-3 years without having to look at replacing them but of course this can vary depending on the type of terrain your lawn has and how frequently you use the machine. 

What can I do to protect my blades?

Whilst there are many factors associated with sharpening lawnmower blades, you want to ensure that you are doing all you can to minimize their wear and tear, so we suggest the following simple tasks to help keep your blades in good condition:

  • Clear Away Debris: Clearing your lawn of any debris such as stones, rocks, branches, and thick shrubbery prior to using your machine.
  • Use a Balancer Tool: Costing little more than a cup of coffee, a good balancing tool will help you realize even weight distribution on the blade and avoid any stresses or fractures when in use. 
  • Consult a Professional: If you are concerned about sharpening your own blades, consult a service provider who can help you and take the stress off you. They will be comfortable with this kind of work and shouldn’t cost you too much either. 
  • Adjust the Height of your Blades: Some machines have the option to change the height of cutting, and whilst many of us want to cut our grass shorter, our blades are less likely to come into contact with debris if the height is adjusted.

How do blades become dull or lose their sharpness?

Over time and exposure to potentially rugged terrain, your blades will lose their effectiveness and you’ll notice your lawn is not looking as fresh and tidy as it once did. Whilst stones and rocks can cause chips and dents, continual use of just general cutting will eventually wear down the metal of the blade. 

Mowing your grass too close to the ground can also have an impact as the blade will also then be cutting through soil and earth, which will likely house stones and rocks which cause abrasion and collision with blade edge and will file the sharpness down. 

When do I need to replace my blades?

You know your lawns and so you are the best person to decide whether sharpening the blade has done enough or whether the time has come to replace. If you are concerned at all over the performance of your blade, and if you feel that further sharpening will cause an imbalance, then it is likely time to replace it. 

It’s important when looking for a replacement blade, that you look for an exact replacement of your current blade preferably from the same manufacturer and as mentioned previously, if you’re unsure or concerned about replacing this yourself, seek the advice of a professional. Even with your new blades, you still need to follow the above advice routinely to ensure optimal blade performance for as long as possible.