Blade sharpening, blunt vs. razor edge

Discussion in 'Lawn Mowing' started by treemonkey, Oct 4, 2007.

  1. treemonkey

    treemonkey LawnSite Member
    Messages: 178

    I wish to share my observations from this summer regarding OEM "blunt" edge sharpened blades vs. shop sharpened "razor" edge blades and see where the debate takes us.

    On my new Exmark Hp 56, the OEM high lift blades came sharpened at 33 degrees and a somewhat "blunt" edge. I mowed about 25 to 30 hours with these before changing out. The blades still looked good and the cut was excellent. I replaced with another new set (to alternate sets) and ran another 25 hours +/-.

    I then replaced the second set with blades sharpened in our shop to the OEM 33 degrees, BUT, with a razor sharp edge. After only about 6 hours use, these blades showed a few tiny nicks and a small amount of "folding over" or metal ridge on the blade bottom in places.

    I did not see a cut quality difference between the "blunt" and the "razor" edge. No tearing and/or tip browning with the blunt blades.

    I'm wondering if the few guys here that recommend sharpening to a "blunt" edge are more correct? Maybe the best sharpening procedure would be to grind the edge to your preferred angle (30 to 33 degrees), then "dress" or "break" the cutting edge with a hand file to maybe a 45 degree or other angle.

    Any opinions???? Sharpen a razor edge every 8 hours vs. every 20 to 30 for a blunt edge????
  2. Nosmo

    Nosmo LawnSite Bronze Member
    Messages: 1,216

    I'd say for my own use if the blade when sharpened to a 30degree angle is razor sharp I'd make one or two passes at 90 degrees with a file. This will blunt the razor edge and should last a lot longer with the slightly thicker edge.

  3. Budget

    Budget LawnSite Senior Member
    from Pa.
    Messages: 368

    I do the same as you.
    You are making two cuttting egdes when done right.
  4. treemonkey

    treemonkey LawnSite Member
    Messages: 178


    What do you mean by "two cutting edges"?
  5. supercuts

    supercuts LawnSite Silver Member
    Messages: 2,814

    by giving it a blunt edge your just taking extra material off the blade. i too notice little difference from razor to blunt, but leaving that little bit extra will lesson the blow against a rock or stump.
  6. Budget

    Budget LawnSite Senior Member
    from Pa.
    Messages: 368

    Use a file to make a 90 deg. angle on the blade will make a top edge and a bottom edge on the same blade. I hope this helps you.:)
    Or if you do a search you might even find a picture of it.
  7. LawnBrother

    LawnBrother LawnSite Senior Member
    from SW Ohio
    Messages: 867

    IMO a blunt or "maintenance" edge is more durable. As you have noticed a razor edge will nick much easier, requiring more frequent sharpening and you have to remove more material to get it right again.
  8. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    Not to interrupt the process, but I believe the folding over actually happens during the sharpening process...
    Next time someone puts a razor's edge on, check it out, that's when I always notice that little lip.

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