Blade on Snapper SPV21675

nbpt100

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This is a walk behind mower. The blade looks like it is on ok condition. No dents or dings in it. Does not look like it hit anything hard. But.....One end seems to be twisted up more than the other. In other words is not symmetrical. I looked up the P/N and it is STEEL WAVE BLADE 1700242ayp. Can anyone confirm if this is intentional and the way it is intended to be made. Thanks.
 

bertsmobile1

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Don't need to lookup anything.
Blade must be symmetrical or they will be out of balance when they spin.
Each side has to weight the same and if possible they should also balance front to back.
 

nbpt100

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Don't need to lookup anything.
Blade must be symmetrical or they will be out of balance when they spin.
Each side has to weight the same and if possible they should also balance front to back.
I am sure both sides weigh the same. One just has more of an upward bend on the trailing edge. it looks really odd. I am not sure how that could have happened by hitting something. Like I said above, the cutting edges look ok.
 

bertsmobile1

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Measure it.
A lump of play doe pushed onto the end of one side should be a neat fit on the other.
If one side has a different flute to the other then it will be under more load as the blade spins so it will be unbalanced in operation.
The blade might weigh the same but the load will be more on one end than the other.
It could be a bad blade.
IT does happen.
 

nbpt100

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Measure it.
A lump of play doe pushed onto the end of one side should be a neat fit on the other.
If one side has a different flute to the other then it will be under more load as the blade spins so it will be unbalanced in operation.
The blade might weigh the same but the load will be more on one end than the other.
It could be a bad blade.
IT does happen.[/QUOTE

Clearly the angle on one side is different than the other. When you say a bad blade are you suggesting bad from the factory? Or something else?

I am thinking I can bend it back to be identical to the other side, which looks normal. Or as good as I can get it.
 

bertsmobile1

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If you can bend a length of heat treated high boron steel forging back into the correct shape then you have a bright future as a 1st class blacksmith.
Hundreds of museums and historical societies will be knocking each other over beating a path to your door.

You would also be the first person on the planet that has actually done it.
But it is your mower not mine so have fun.
 

nbpt100

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If you can bend a length of heat treated high boron steel forging back into the correct shape then you have a bright future as a 1st class blacksmith.
Hundreds of museums and historical societies will be knocking each other over beating a path to your door.

You would also be the first person on the planet that has actually done it.
But it is your mower not mine so have fun.
Okay, Lots of sarcasm. I can play that game too. But I won't! I am too busy trying solve a problem. I do know someone who has bent them back. But he says it is usually not worth it. I just want to use it today and not have to wait for a new balde.
 

ILENGINE

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Unless I have overlooked a link a picture of the offending blade would be handy.
 

bertsmobile1

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Okay, Lots of sarcasm. I can play that game too. But I won't! I am too busy trying solve a problem. I do know someone who has bent them back. But he says it is usually not worth it. I just want to use it today and not have to wait for a new balde.
Some times it is necessary to make people stop & think.
You are not the first person who would think, "no worries, I can just bend it back " without the faintest idea of what your are actually doing.
To most it is just a lump of steel & steel bends dosn't it ? So naturally I can bend it.

Well yes it bends.
It also springs back
And it has to be balanced within a very fine tollerance
If it has bent in service then structural damage has been done to the internal microstructure.
Bending it back makes this damage worse
It is not a fender
The thing is spinning at close to 200 mph and you are only a foot or so away from it.
At the best the out of balance will cause the crank to wobble and flog out the lower bush then chew up the oil seal then dump the oil.
At the worst the blade can fracture and send schrapnel flying at 200 mph.

Mowers are not rocket science but blades are. The metallurgy & engineering that goes into them is amazingly complex.
I imagine some where on the web will be information about blade making put out by the factories that make them.

If you were about to jump onto a place & saw the pilot smacking the propeller to knock it back into shape would you get on the plane ?

At a rough guess I would put my money on the blade being defective from the factory and slipped past quality control as it would be rare for a flute to twist in use.

And just because you know some one who has apparently gotten away with it does not mean that it should be done nor that it is safe to do it or even that it was done properly or that in 1,2,3,4 years down the track the damage that the "repaired" blade caused became apparent.
It took near 20 years for metallurgists & engineers to convince the government down here that bending an aluminium motorcycle wheel back into shape should never be done.
However around 40 young men died from wheel failure before anyone took notice & legislation was enacted .

There is a very sound reason why your owners manual warns about using a blade with any signs of damage & it is not just to avoid being sued.
 

Mow Joe

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In all the years I spent in the mower business, I never saw a "bad" new blade. Your blade is bent because it hit something. A tree root, or maybe being run aground into some tough turf, often won't ding the edge of the blade. I won't get into the science part of it, but trying to straighten it is difficult, if not futile...I've tried. Usually, when vibration comes along with a bent blade it's because the crankshaft was bent along with the blade. A twist in a blade causing a noticeable vibration, I don't buy into at all.
 
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