Blade balancing

Discussion in 'Mechanic and Repair' started by rootytalbot, Apr 28, 2013.

  1. Pietro

    Pietro LawnSite Senior Member
    Posts: 858

    I keep my spindles greased and have never balanced a blade. I've got a magnamatic 9000 sharpener. We sharpen the blades and just mount them. Never balanced a blade ever, all my toros cut great.
     
  2. rlitman

    rlitman LawnSite Bronze Member
    Posts: 1,501

    RPM is only a small part of the story to.
    The issue with balance is not so much how fast the part rotates, but how far the imbalance is from the center. Car wheels are not only larger in diameter, but they also have a large amount of rotating mass that is far from the center. They also have thickness that creates vibrations that do not exist in a relatively flat mower blade.

    I agree that the nail method is useless. The stepped cone method is fine, IF the steps in the cone align with the hole in the blade's center as well as the bolts.

    That is actually a big issue on car tire balance. On some vehicles, the center of rotation is not hub centric (which would be aligned on a balancer's centering cone), but lug centric. So, if your balancer is perfectly aligned with the center of the blade's center hole, but that hole isn't aligned with the center of the shaft (because of how the bolts line up), you won't be balanced.

    BTW, your balancer looks like a pretty sweet setup. The way the chuck approaches the blade works in the same way as the cone retracts into a car tire balancer's hub. Yes, a cone without steps has the potential to center better, but only if something holds the cone straight. Just like that. I use a dial indicator to measure runout on my wheels, but that indicator stick is actually a great idea to check for a bent blade. Just turning the blade 180 degrees will only tell you if one side of the blade is bent up or down. If you leave the indicator in place and flip the blade over, you can see it's "dish" too (how much the blade is out of plane)
     
    Last edited: Apr 30, 2013
  3. ed2hess

    ed2hess LawnSite Fanatic
    Posts: 12,962

     
  4. Blade Runners

    Blade Runners LawnSite Bronze Member
    Posts: 1,021

     
  5. rlitman

    rlitman LawnSite Bronze Member
    Posts: 1,501

    How does hitting a rock throw a blade off balance? It may deform the blade a little, but balance is based on weight distribution. If hitting a rock was always enough to rip a large enough chunk of metal off the blade to effect balance, you're in for a lot of problems.

    Balance is more likely affected by one side of the blade wearing faster than the other (if the blade is off angle and one side always cuts first), or grinding one side more than the other.
     
  6. Pietro

    Pietro LawnSite Senior Member
    Posts: 858

     
  7. caseysmowing

    caseysmowing LawnSite Bronze Member
    Posts: 1,849

    I can see doing it on a push mower but not on a bigger mower. They get caked with grass in two seconds anyways. Someone mention about cheap china spindle bearings. I'm pretty sure scag uses timken bearings which I believe are made in the USA and are the best in the industry. Don't quote me on that just what I've read.
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