Replacing the blade on your lawnmower is usually a simple task, but a lawn mower blade that's stuck requires some elbow grease and the help of some extra tools, most of which you have at home.
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Lawn Mower Blade Stuck?
A lawn mower blade can get stuck for several reasons, one of which includes over-tightening. Lawn mower blades are supposed to be loose enough to slip when they hit a solid object in order to protect the engine and the blade itself from damage. Lawn mower blades may also get stuck if the bolt is threaded the wrong way. Single blade walk-behind mower bolts are right-hand threaded; this means that in order to loosen it, you will have to turn it to the left.
Some twin-blade walk-behind mowers and lawn tractor mowers have both left-hand and right-hand threaded blades. To tell which blade you have, note which direction the blade cuts grass. Blades that turn left have a right-hand thread, while blades that turn right have a left-hand thread. Rounded bolts could also be the culprit – this may occur if the bolt is old and falls victim to corrosion or if the tool is old or damaged, the wrong size or the wrong tool for a stuck bolt.
Removing a Stuck Bolt
Before you attempt to remove the bolt, make sure that it is safe to do so. Remove the plug wire and set it aside. If the mower has a gas tap, turn the gas off before proceeding. Turn the mower on its side so the carburetor is facing up to keep gas from leaking.
Check the status of the bolt. If there is rust around the bolt, remove as much rust as you can with a wire brush. Then, spray the bolt with WD40 or a similar penetrating oil product, taking care to cover above and below the blade and making sure to give it time to seep into the threads. Once you have sprayed the oil product, you may attempt to remove the bolt again with a socket wrench, or try one of the methods below.
Remove a Stuck Blade with Leverage
A breaker bar may help leverage and loosen stuck bolts. Breaker bars are an extension to a socket wrench that gives you a longer handle to apply more leverage. Immobilize the blade by wedging a piece of scrap wood between the mower blade and the mower deck. Once it's secure, place a socket wrench over the bolt, (making sure it is the correct size), and attach the breaker bar to the socket.
Use the breaker bar as the socket wrench handle and loosen the bolt. Once it is loose, unthread the bolt by hand and remove the blade.
Remove a Rounded-Off Bolt
If the wrench cannot grip the bolt, tap the side of the bolt head with a hammer instead after spraying it with penetrating oil. Be careful not to damage the bolt.
However, if the wrench continues to slip, apply more oil to the bolt. Then, use a pair of vice grips, (also known as locking pliers), and adjust the tension so it can securely clamp over the head and turn.