Blade-balance oddity
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Jimmy the Lock
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The blade is going to be spinning horizontally on the mower so seems like that would be the thing to focus on when balancing which should be a matter of trying to achieve equal weight distribution across the entire blade.
When you buy new blades, are they balanced at the factory?
When you buy new blades, are they balanced at the factory?
It is gravity. Maybe it would help if you think about objects floating in liquids, rather than being suspended in air, like you do when you attach the blade to your balancer. If you threw a two by four in a pond it would float horizontally, not vertically, unless you attached an even heavier weight to one end. Everything is being pulled to the center of the earth (not counting the much lower gravitational pull of other heavenly bodies, like the moon and sun). Your balancer is set up plumb, in other words, in alignment with and pointing at the center of the earth. The cone on the balancer aligns the blade so that its center is perfectly centered (assuming the blade was correctly manufactured and that the blade hasn’t been deformed). The bearings allow the blade to react to gravity without falling to the floor, just like the pond water allows the 2x4 to float horizontally as gravity evenly pulls it to the center of the earth. The higher density of the water prevents the wood from falling below the water’s surface. An out of balance blade has two uneven halves. The one with the greater mass is pulled with greater force by gravity than the one with less mass, leaving the heavier half pointing to the earth’s center. Balance the masses of the halves and you have a blade that ”floats” like a uniformly dense piece of dimensional lumber on a calm water surface.
Jimmy the Lock
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Yes, and if the blade has equal weight distribution across the entire blade then it should be balanced and spin smoothly without vibration.
I balance every new blade I buy. One in twenty might be close enough to use. I user a $200 balancer. I balance tip to tip, like you do. But sometimes, the center hole is off center, rarely, but enough to make the edge of the blade at the hole heavier on one side. I've never had it off enough to matter, but a few times, for the fun of it, I would grind a little bit off next to the hole, and get the blade very balanced. But the mower never seemed to notice.
I've never seen a new blade that was balanced. Maybe it'd be if it was hung from a nail, but not on my balancer.
Jimmy the Lock
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So how much grinding is typically needed to get one to balance?
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Just depends how bad it is out balance due to wear. Some it a little and other it takes a lot. Even new blades are sometimes out balance according to my balancer. You first correct cutting edge and then sneak up getting them near prefect balance by grinding the heavy end further while keeping about a 35 degree cutting edge angle.
But i hate try to sharpen those 1/4 thick blade as they can up to 30 minutes to correct them.
But i hate try to sharpen those 1/4 thick blade as they can up to 30 minutes to correct them.
Gord Baker
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Gord Baker
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Yes. It will be fine. Run it.