How to Sharpen a Lawn Mower Blade

Lawn Mower Blade Sharpening

Video: How to Use Oregon Blade Sharpening Belt Grinders

Belt grinders are easier to use than traditional stone wheel grinders. This machine is ideal for lawn mower blades and chainsaw bars.

Tools Required

Before Sharpening Your Lawn Mower Blades with a Blade Grinder

Step 1

Check the work area. Make sure the grinder is properly supported on a flat and level work surface.

Step 2

Make sure that there are no:

Flammable materials such as shop rags, gas cans and other solvents.
Objects or people nearby who are positioned close enough to be hit by sparks or debris.
Loose objects (including your clothing or hair) that could get caught in the grinding wheel.

Step 3

Inspect all aspects of the grinder. If any of the following questions can be answered with a “yes”, do not operate the grinder.

Are there breaks in the insulation or exposed wires on the power cord?
Is the cord’s ground terminal broken or damaged?
Is the stone cracked or chipped?
Are any of the guards missing or damaged?

Step 4

Check the tongue guards for clearance. Tongue guards on the top of the wheel should be positioned no more than ¼ of an inch away from the stone. The bottom guard which connects to the work table should be positioned no more than 1/8 of an inch away of the stone. If the clearances aren’t adjusted to the specifications above, do not use the grinder.

Follow these steps to adjust the guards:

Check that the power is off and the lock is removed before adjusting the guards.
To adjust the guards, loosen the nuts which hold them in place.
Slide the guard toward the stone within the proper dimension. (If you don’t know what this distance should be or the stone is so worn you can’t achieve the proper distance, don’t use the grinder. Only continue after you have confirmed that the tongue guards are properly adjusted.)

Using the Lawn Mower Blade Grinder

Note: These instruction are written in order to give a general overview of the steps involved in using a lawn mower blade grinder. They are not intended as a replacement for your blade grinder’s user manual.

Step 1

Determine whether the lawn mower blade is left-handed or right-handed. On a flat surface, lay the blade so that the bottom side of the blade (aka the flat or “grass side”) is down against a flat surface. Position the blade so that it is extending away from you (as if each end were at the “12” and “6” positions on a clock). lf the straight (cutting) edge on the far end is on the right, it is a right-handed blade. If the edge is on the left, it cannot be sharpened with the Oregon 88-025 Lawn Mower Blade Standard Duty grinder. Check your blade grinder manual for details.

Step 2a

Adjust the grinding angle for the blade. The blade to be sharpened will determine the angle the machine is set at. All Oregon blades, are ground at 30 degrees.

Step 2b

Set the blade on the table and match its angle to the stone face. It should look as if the stone is directly touching the grinding edge. If it is not touching from top to bottom, the angle needs to be adjusted. In order to change the grinding angle, you will need to loosen the two tower nuts and turn the top adjusting screw to raise or lower the stone and motor. Consult your manual for details. Once the correct angle is achieved, recheck the adjustment of the guards and plates and retighten the tower nuts.

Step 3

Plug the power cord into an approved outlet. Place the safety lock pin in the power switch.

Step 4

Set the motor switch to forward or reverse. For normal, right-hand cut blades (those with the cutting edge on the right side), the motor switch should be set to the forward position. This rotates the stone counterclockwise, drawing the blade toward the stone so that sparks are thrown to the opposite side of the mower blade.

Step 5

If your lawn mower blade grinder has a light attached, adjust it to the correct position.

Step 6

Stand facing front of the grinder – never on the sides. The face of the grinding wheel should be in front of you. Standing this way ensures you are out of the path of any material thrown from the grinding wheel.

Step 7

Turn the switch to the “on” position. Let the motor and stone come to full speed.

Step 8

Hold the blade with both hands positioned on the opposite end of the area you intend to sharpen.

Step 9

With the motor at full speed, lay the blade flat on the table (grass side down) at 90 degrees to the one inch stone face.

Step 10

Pass the cutting edge blade edge back and forth in the direction of the grinding wheel, removing material with each pass. Hold the blade so the cutting edge is parallel to the surface of the grinding wheel. If the motor switch is set to the forward position, the sparks will be thrown out on the work table to the right. If you have the optional grit collector, it can be placed to the side of the grinder. This will help keep your work area much cleaner.

Step 11

Continue to pass the blade across the stone until the edge has all the nicks and dull spots removed. The blade edge should not be razor-sharp – a .030 inch to .045 inch edge is recommended.

Step 12

Turn the mower blade and repeat the process on the opposite end. Try to make the same number of passes that you made on the first end.

Step 13

Switch the grinder off.

Step 14

Check the mower blade for correct balance. Use a blade balancer (such as the Oregon 42-047 Precision Blade Balancer). Push the magnetic unit back, then center the blade on the cone. Pull the magnetic hold unit into position and then, holding the blade horizontal, release it. If one end of the blade drops down, that end needs to have more material removed from it. Remove the blade from the balancer making note of the heavy end.

Tip: Balancing mower blades protects your mower from harmful vibration and wear.

Step 15

Go back to the grinder and slowly remove material from the heavy end. Remove material from the sharpened edge only. Never grind material from the ends or back of the blade. Check frequently until you achieve a balanced blade.

Step 16

When you are finished sharpening, turn off the grinder switch and remove the safety pin.

Tip: Removing the safety pin will prevent accidental starting or unauthorized use of the grinder.

Step 17

Turn off the light and clean the work area of grit and dust.

FAQs

How Sharp Should Your Mower Blade Be?

Mower blades should be aggressively sharp, but not as sharp as a razor’s edge. You should be able to touch the blade with your hand without getting cut. Contrary to popular belief, a lawn mower blade with a razor sharp edge will not cut grass better. In fact, an edge that is that sharp has the tendency to roll over, which can cause blades to get nicked and chipped. Additionally, lawn mower blades that are too sharp get duller, faster resulting in the need to sharpen more frequently and a shorter blade life.

Warning WARNING: Make sure your lawn mower blade grinder is always turned off before you perform any maintenance.

How Often Should You Sharpen Lawn Mower Blades?

How often you sharpen your lawn mower blades depends on your frequency of use. If your lawn mower is only used at home, you probably only need to sharpen your blades once a year. If you are a professional, you will need to sharpen your blades more frequently. Once you notice a reduction in cutting performance, it’s time to sharpen your mower blades. Damaged blades should be replaced immediately.

What tool do you use to sharpen mower blades?

The best way to sharpen a mower blade is with a dedicated blade grinder. A blade grinder is the best tool to use because it can maintain consistent sharpening angles.