How Sharp Should a Lawn Mower Blade Be? (Solved & Explained!)

A lawnmower blade should not be razor sharp. Rather, you should feel that it is definitely sharp, but not enough so as to cut your finger when you feel the edge. If you aren’t certain what the factory-level sharpness was, try to make your blade as sharp as a butter knife and this should be just about perfect for cutting the lawn.

For the rest of this article we’re going to focus on sharpness – what is too sharp, what dull blades can do, and how often you need to sharpen and replace your blades. Read on to find out everything you need to know when it comes to mower blades and your lawn!

Should lawn mower blades feel sharp?

Yes, mower blades should feel sharp, but they should never feel razor sharp. You should be able to trace your fingers and notice an edge, without it being sharp enough to cut your finger. A common novice mistake is sharpening mower blades to razor sharpness and this should not be done

It thins out the metal, making it more prone to damage, and the oversharp blade will become dull very quickly.

Can a mower blade be too sharp?

Yes. A razor edge on a mower blade is going to be much more prone to damage. It is best upon purchase of new mower blades to feel the edge that the manufacturer has put on them and use this as your guide when it comes time to sharpen them.

Oversharpening your blades will reduce their overall life, so try to reproduce the factory edge as closely as possible for best results.

Are new mower blades sharp enough?

Yes, newly purchased mower blades will come ready to use, with their edges already sharpened to the optimal sharpness by the blade’s manufacturer. You can install the blades and use them right away, just make sure that you sharpen them after 20 to 25 hours of use and you’ll get the best life and performance out of your blades.

How do I know if my lawn mower blade needs to be sharpened?

Dull blades tend to rip at grass, rather than cutting it cleanly, though the first sign will generally be that the mowing will look a little uneven. If you see these, give the blades a physical assessment to look for dents or nicks, and go ahead and sharpen them to see if this resolves the issue.

Note: If your mower appears to be pulling grass out by the roots, stop mowing immediately and sharpen and balance the blades, as this is a definite red flag and your lawn and mower can both be damaged during this time.

Should mulching blades be sharp?

Mulching blades need to be kept sharp, just like any other blades. They do not require a special schedule of their own, but rather the same sharpening schedule as you would with standard mower blades. For every 20 to 25 hours of use, remove the blades and clean them, followed by sharpening them before using the mower again.

Are new lawn mower blades balanced?

Yes, new mower blades come from the factory fully sharpened, balanced, and ready for immediate installation and use. This is a great time to feel the edge to see what sharpness you should go for when it’s time to sharpen the blades, and you can even take a couple of pictures with your phone to remind you.

What angle should a lawn mower blade be?

Lawn mower blades come to you from the manufacturer with a model-specific angle to the edge, which will typically fall in the range of 30 to 35 degrees. If you aren’t certain, however, it is easy to tell. Simply hold your sharpening file against the current angle to the edge and you’ll know exactly how to hold your file during sharpening sessions.

What is the best way to sharpen lawnmower blades?

A bench grinder is the fastest and most efficient means of sharpening your blades, but a handheld angle grinder is inexpensive and a very close second. You can typically find a nice, portable angle grinder for under $60 and it will save you a lot of time filing if you invest in one for sharpening your mower blades and DIY tools at home.

What does a dull lawn mower blade do?

Dull blades can cause all kinds of damage to your lawn. Most often, the dull blades will rip and tear at the grass, cutting unevenly and damaging your lawn. It might not be apparent at first, simply looking like a low-quality cut, but typically the grass will begin browning fairly quickly.

 Dull blades can also rip out grass by roots if you are very unlucky, so be sure to sharpen your blades or have them sharpened at your local hardware store every 20 to 25 hours of work use to avoid these issues.

Are mower blades pre-sharpened?

Yes. Mower blades some pre-sharpened, pre-balanced, and ready to go. You won’t need to sharpen them on your own until you have used them for 20 to 25 hours o mowing and with standard blades, you can expect 100 to 200 hours of work use before the blades will need to be replaced.

Commercial grade blades are also available and these incorporate tougher metal alloys, extending life to up to 400 hours in some cases!

How much does it cost to sharpen a lawnmower blade?

Getting your mower blades sharpened professionally is inexpensive and can save you time in a pinch. Expect the costs to run anywhere between $5 and $15 for standard mower blades, while mulching and commercial grade blades will run you a little more (although check around, as this varies quite a bit depending on the vendor).

What’s the difference between mulching blades and regular blades?

Standard mowing blades tend to be rectangular and straight, while mulching blades will typically have a noticeable curvature to them, as well as an extended and even extra cutting edges along the length of the blade. Mulching blades also have ‘teeth’ that help in shredding leaves and which face up when installed underneath your mower.

John Deere mulching blades are a rare exception, as they are rectangular and smaller on one side, but such exceptions are uncommon.

Do you sharpen both sides of a lawn mower blade?

No. The cutting edge on your mower blade is only going to be sharpened on one side and you can place your file against the existing edge so that you will know exactly the angle in which this needs to be sharpened.

Sharpening both sides is not necessary nor recommended, just focus on the existing edge and sharpen it to the factory edge if you remember it or to the same sharpness as a butter knife, if you don’t.