How to Sharpen a Lawn Mower Blade

Keeping your lawn mower's blade sharp is an important part of yard maintenance. When you mow a lawn with a sharp blade, it helps the grass stay healthy. Dull blades rip the grass and make it more susceptible to disease, while sharp lawn mower blades cut grass evenly and quickly.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• Wrench
• File
• Blade balancer

1. Remove the spark plug wire on the front of the engine. With the spark plug wire removed, the engine won't start. This prevents injury while you are sharpening the blades.

2. Detach the blade from the bottom of the lawn mower. Use a wrench to loosen and remove the nut and bolt holding the blade in place.

3. Sharpen the blade with a file following the angle of the edge. If the angle is worn down it should be at 45 degrees.

4. File each side of the mower blade the same number of times. If the sides are filed differently the blade be off balance.

5. Re-attach the blade to the bottom of the lawn mower. Secure the nut and bolt to hold the blade.

6. Balance the blade with a blade balancer. If the blade is not balanced, file a little of the heavy side and try again. The lawn mower vibrates if the blade is not perfectly balanced.

7. Replace the spark plug wire and try out your new, sharp lawn mower blade.

Tips & Warnings

• Lawnmower blades should be sharpened every 10 uses depending on the thickness of the grass.
• Blade balancers can be purchased at any hardware store.
• Be careful when handling the blades. They can cut you even if they are dull.

Resources

• Learn lawn mower basic care and maintenance.
• Find tips and hints for lawn mowers.

[Forumtroll]

on 8/6/2008 (Blades are cheap - prosthetic legs are NOT)

#5) Pay attention to 'lines' on the blade that indicate maximum material removal. Some blades have 'lines, markers, or groves' to indicate the minimum amount of material for blade replacement. (The blade acts as a balancer and you can damage things by taking off too much metal).

How to Balance (more detail):
Before you replace the blade you should find a flat level surface without any wind. Place the blade balancer on this surface and use:
A) the bubble at top (if it has one, it is worth the money so get one with if you can) or
B) a tape measure and measure from the surface to the blade (under 1/4 of an inch is best).
Some blades have "Nicks" on the back side that are intended to balance the blade by filing a small amount of these grooves or nicks. Otherwise file a small portion of the angled side of the blade and then recheck

[Forumtroll]

on 8/6/2008 The blade should be like the blade of a good pair of scissors (Like /_ not like < ) Normally blades are flat on the bottom side and have a 45 deg (or more) angle on the upper side (never use less than a 45 deg angle, it makes the material too thin and wears faster). knifes and razors have two angles filed together.

Also note:
#1) The instructions as given are a bit off; do "6" and then "5" - never put an unbalanced blade on a lawn mower. Unbalanced blades can damage the motor, or break the crank and fly off.

#2) I would also suggest STRONG LEATHER GLOVES as the blade can and will cut you during removal and replacement.

#3) CHECK THE THREADS. Some lawnmower crankshafts have normal threads, others have reversed threads (tighten means loosen).

#4) NEVER try to sharpen, straighten, or re-use a blade that has a large nick, crack, break or bend. (Blades are cheap - prostheti

[mikeg1014]

on 5/13/2008 how sharp should the blade be? Like a razor or what?