Another Question Concerning Blade Sharpening

Discussion in 'Lawn Mowing' started by MOturkey, Oct 6, 2012.

  1. MOturkey

    MOturkey LawnSite Silver Member
    Messages: 2,782

    Okay, I know this topic gets worn out on here, but I'm interested in getting some more information on something. I have a Magna-Matic sharpener and try to replicate as closely as possible the factory edge on the OE blades I use. In other words, I sharpen the blade to somewhat less than razor sharp.

    I think most of us are aware that if you overheat a blade during the grinding process to the point of discoloring the metal, you have removed the temper, and the blade won't hold an edge as long. I also realize quenching the blade in cool water can help reduce the likelihood of this happening. My question is, for those knowledgable on the subject, is there any benefit from quenching even if you don't have a problem with heating the edge to the point of discoloration? In other words, does the heat produced from grinding soften the metal over time even at lower temperatures?

    It seems to me that as my blades get more worn, they don't hold an edge as well, and get more nicks and dings than newer blades. This observation isn't scientific. I've never tried to keep track of the hours etc, not sure if it would be possible anyway due to the wide range of conditions the blades encounter on a daily basis, but it just seems to me like my blades that are close to the end of their useful life tend to need changing out more often than blades I've just put into service. Thanks for any input.
  2. PlantscapeSolutions

    PlantscapeSolutions LawnSite Gold Member
    Messages: 3,012

    I find if you care about quality and want to minimize the amount of grinding you do then daily sharpening is a must. The Magna-Matic is not a machine for sharpening blades that are allowed to become really dull.
  3. williams lcm

    williams lcm LawnSite Bronze Member
    Messages: 1,200

    I personally sharpend my blades to razor sharp. I have not noticed them dulling any faster. Yes they sometimes turn blue while sharpening but I sharpen daily and have never had a problem.

    THIESSENS TLC LawnSite Senior Member
    Messages: 892

    if your quenching the blades in cool water, you are hardening (annealing) the blades and causing them to become very brittle which will increase the nicks you are getting. If you dip them in oil instead of water, you are still hardening them but not as quick as water. water shocks it almost instantly, which makes it very brittle. water will make it extremely hard but can also cause it snap, crumble etc. if hit hard. oil will still harden the blades but at a slower rate, and will not be as brittle. hope that helps...probly not the answer your looking for, but thats what i know.
    happy thanksgiving!
  5. IMO there isn't need for razor sharp. I sharpen mine till the edge is sharp, and get a solid 8 hours of machine use, most of the time 10. Razor sharp is gone after you start the first lawn.
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  6. Ridin' Green

    Ridin' Green LawnSite Fanatic
    Male, from Michigan
    Messages: 17,807

    I agree with this.

    They should feel nice and sharp to the touch, but not so sharp that you can't slide your finger down the edge using moderate pressure without cutting it. All my Deere manuals have always said 1/64" edge is ideal, and over the years I've found that is about exactly the amount of the square/flat edge left on the cutting edge you end up with, if you sharpen your blades to like what I described at the start of the post.
  7. Sprinkler Buddy

    Sprinkler Buddy LawnSite Bronze Member
    from Florida
    Messages: 1,185

    I too use a Magna-Matic sharpener for a # of years now. I haven't noticed this problem your having. Maybe it's the quality of the blades that your using. I have found that some after market blades hold their edge much better than others. Are you using a high or mid-lift blade? In sandy conditions like we have in my area, I use a low lift blade to keep from dulling the blades as quickly by picking up so much sand and they also make my mower decks last much,much,much!!! LONGER!

    Despite what many of the shop guys tell you, they mulch just as well also. Cracks me up when I hear them telling folks how much better these high dollar mulching blades work.
  8. kawakx125

    kawakx125 LawnSite Bronze Member
    Messages: 1,130

    i have a hard time believing anyone who sharpens to nearly razor sharp doesn't have problems with chipping and dulling quickly.
  9. Greg78

    Greg78 LawnSite Silver Member
    Messages: 2,010

    Tried em all low, med, high lift, gators and wavy mulch blades. By far wavy mulch blades work the best with a full kit.
  10. Ridin' Green

    Ridin' Green LawnSite Fanatic
    Male, from Michigan
    Messages: 17,807

    True that.

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