How to Safely Sharpen Lawn Mower Blades (5 Safe Step)

How to Safely Sharpen Lawn Mower Blades

Last Updated on May 16, 2022 By Emma W. Thomas

After a year of using your lawnmower, you may notice that it no longer cuts like the first day and that it has lost efficiency and performance. Do not worry, this is normal, the most likely is that the edge of your mower is a bit worn and shows notches or notes that it is somewhat blunt.

It’s time to sharpen the blades of your lawnmower! For this, we will give you all the tips so that you get a perfect result, How to Safely Sharpen Lawn Mower Blades

How to Safely Sharpen Lawn Mower Blades

Before performing any work in which you have to use tools and may pose a danger, we recommend that you use all necessary means of protection, such as gloves, glasses, etc.

First of all, you must take into account if your lawnmower is gasoline or electric. Since if it is gasoline the first thing you should do is empty the tank. For the disassembly of the blades, you must lay the lawnmower to the side. If you forget this simple step, you can spill gasoline on the ground.

Now that you have your lawnmower’s tank empty, let’s disassemble the blades step by step:

To avoid accidents and the machine to start, we will disconnect from the current if the cutter is electric or disconnect the spark plug in case you have a gasoline lawnmower.

Now lay the lawnmower to one side and place a wooden block blocking the blades so they cannot turn freely.

Then loosen the blade bolt by turning it counterclockwise and don’t forget to put a piece of tape or a little spray to mark the bottom of the blades. (it is a very typical mistake to turn them upside down and mount them again).

Finally, clean the blades to remove the remains of grass or mud that may be left using a rag and some soap and water if necessary. Dry them well if you use water to clean them.

We already have the blades out of the machine! Now the most important thing is sharpening. For this task, we recommend that if you are not very handy, take them to a professional who sharpens them. For the most launched we will give you all the tips to leave them perfect.

essentially the blades can be sharpened in two ways, by hand or by machine

Sharpen Blades by Hand

First of all, you must securely fix the blades to a vise or sergeants or something similar. The objective is that they remain well fixed and do not move while we work.

Then use a metal file to sharpen the blades. Move the file at a 40-45 ° angle until the bright edge is left and the notches that had been produced disappear.

It is very important that you do not sharpen the blades too much (it is not that you leave it as a ham knife), so that you notice the sharp edge is sufficient since the rotating blades will cut the grass without any problem.

Sharpen Machine Knives

Sharpening the blades with machines is a process similar to sharpening them by hand, but obviously with some kind of power tool. We are going to give you 3 options so you can choose the one you like best.

First of all, wear glasses and gloves to avoid any kind of accidents, since the filings of the blades can jump and enter the eyes or cause an injury.

Fix the blades well to your work table using a bench screw, sergeants, or the system you prefer, but they are well secured.

Now we can use these 3 machines: a metal disc grinder, a belt sander, or a Dremel with a special mower blade sharpening accessory, which gives the perfect sharpening angle.

If you use the grinder or belt sander, you must sharpen at an angle of 40-45º until the edge is bright and not notched (remember not to sharpen too much).

If you prefer to use a Dremel, it is not necessary to look at the cutting angle, since there is a special accessory for sharpening garden tools (675)  that gives the optimum angle of sharpening so you do not have to worry if you are doing it or not correctly.

Once you have sharpened the blades of our lawnmower, it is time to assemble them again.

First place the blades in their correct position. You will not have problems if you marked them with some tape or spray as we indicated in the disassembly step.

Lubricate the area of ​​the main bolt with a bit of WD 40 or 3 in 1 type lubricant to prevent rusting in the future and to loosen the bolt without problems next time.

Finally, tighten the bolt clockwise with the tightening torque indicated by the manufacturer, which is usually 70 Nm. Use a torque wrench for this. If you do not have this type of wrench, make a firm tightening and make sure the blades can turn freely.

You have sharpened the blades of your lawnmower! You just have to know a couple of things.

The blades should be sharpened once a year and a maximum of 3 or 4 times throughout their useful life, after this it is better to change them and put new ones, since their effectiveness can be affected.

How to Safely Sharpen Lawn Mower Blades A Short Video

When using power tools for sharpening, the blades can become very hot and weak, be careful and cool the area with a little water if necessary.

Now you just have to enjoy your lawn mower and maintain a garden in perfect condition with much less work than with poorly sharp blades.