My Black&Decker electric mower was loan to friend. He ran the
mower over several boulders several times, chipping a couple
pearl size sections off the blade. Possibly, this is causing the mover
to vibrate to the point of causing a shoulder sore.
I remove the blade, then clamp it to a vise grip. I have an angle
grinder that I will use to fix the balancing problem. The problem is,
I've never done this before. What is a practical way to balance a
Sears and other places that sell mowers will sell a small cone shaped device
on which you position the mower blade before and after grinding to determine
if it's balanced, probably not more than $5 I would guess.
Hate to be the bearer of bad news, but the odds are that the severe
vibration that you are experienceing is not due to an out of ballance
blade. When a mower hits an object like a root, or rock or other
obstruction, it often bends the crankshaft that the blade is attached
to. This happened to my parents Honda mower when my son ran it into a
rock and the repair guy told us that it is a common occurance. In their
case it required a fairly expensive repair, the replacement of the crank
shaft AND a new blade. You can try a new blade, and maybe you will get
lucky, but if he hit rocks numerous times, I expect that the vibration
will still be there with the new blade. They don't make the motors on
mowers with heavy enough parts to be mowing rocks.
This is Turtle.
I take the blade off and bring it with me to Walmarts and go to the lawn mower
area and match it up and get a new one for $9.95 and come back and put it on.
Tring to balance a blade on a lawn mower with chunks missing is right next to
Now like Randy said it might be a bent shaft on the motor.
Your mistake was loaning the mower. Your "friend" owes you a new one,
or at the very least should take it in for repair. You may have a
bent shaft and in that case the mower is trashed.
You can buy a balancing cone made specifically for mower blades.
These work well. Or, you can use the shaft of a screwdriver to
balance it, but the cone works better.
I use an old knife blade clamped in the jaws of a vise. I then balance
the blade with the knife edge running across the center of the hole. Grind
the edges to balance. You will never get the blade to sit stationary but
you will see which end is heavy. If the mower is shaking enough to feel in
your shoulders I suspect that the motor shaft is bent.
If it is a serious wobble I'll put my money on a bent motor shaft rather
than an unbalanced blade. I have a battery-powered electric sold by
Sears but IIRC made by B&D and hitting a tree root with it left me with
a bend in the motor shaft which was unrepairable leaving me to replace a
very expensive motor. I'm a lot more careful now...
Replace the blade. A blade that has been that badly abused may have had
its integrity compromised. You can bank on that blade being severly
weakened. If you try to balance it and use it, you are running the risk of
a catastrophic blade failure in the future, which means that it is possible
that chunks of metal could come flying out from underneath the mower.
It is possible that the shaft is bent; however, some lawn mower engines
have small aluminum 'keys' that sit in slots machined into the shaft (or at
least where there is a mechanical connection between the shaft and the
engine). These are designed to fail if the blade strikes something hard.
It happened to me once. I hit a metal culvert and the mower stopped dead
and would not restart. Once the keys were replaced, everything was fine.
Don't know how big "pearl size" is since pearls
come in a lot of different sizes. You're going to
have to do a lot of grinding to get it in good
shape and balanced.
To balance it, just clamp a six or eight penny
nail in a vice (horizontal) with about 3/4"
sticking out. Or, pound the nail into anything
and stick the center hole of the blade on it. You
can get fancier but a nail works. Set the blade
slightly off horizontal and grind until the side
that is down always swings down (try each side
slightly below horizontal).
Finally, you may have a worse problem than just
chips in the blade -- the crank shaft may be
slightly bent. Be sure you get the blade balanced
well, because you need a balanced blade to tell if
the crankshaft was bent.
I dought it is the blade probably the rotor shaft, A new motor is in
order but at the price of parts a new mower your idiot friend owes you.
He wont be your friend now. And you wont loan out your stuff. My
neighbor wanted to borrow my mower I said its broke, He borrowed someone
elses and I heard him hitting rocks for an hour stalling his loaner
Dave HVac electric motors dont have Crankshafts.
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