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question about how blades cut

Discussion in 'Lawn Mowing' started by mikeshere89, May 29, 2003.

  1. mikeshere89

    mikeshere89 LawnSite Member
    from iowa
    Posts: 117

    my question is on my exmarks the blades dont overlap like my friends john deere, althou i have never had any problems with grass not cut in the middle of the blades i am curious why john deere would have them overlap, my friend's blades hit a tree and broke a belt which in turn made the belts collide together, basically bent both blades and made a horrible noise. to me this is poor design by jd.but it makes me wonder how exmark and im sure alot of other mowers dont have to overlap there blades, i know they are really close together and the tip speed has everything to do with the cut, im just surprised i havent had any problems, also i dont like jd cause u have to buy there type of blades made for jd, any comments would be great.
  2. Cut This!

    Cut This! LawnSite Member
    Posts: 48

    One blade is in front of the other so there is overlap. If you stand in front of your machine and look directly at it, you'll see both blades cut a small section in between so there is no grass left uncut.

    The only reason to used "timed" blades like the JD is to keep the machine's overall length shorter. It costs more to use timed drives.
  3. greenman

    greenman LawnSite Addict
    Posts: 1,405

    I agree with that Cut This, BUT what about the the decks that have only 2 blades, like the 36 and 32? How do they cut all of it without leaving a strip in the middle? I think this is what Mikeshere means.
  4. BSDeality

    BSDeality LawnSite Silver Member
    Posts: 2,850

    my gravely has a 1/4" gap between the blades, i think just the lift from the blades pulls them in towards the center of the blade and then they get chopped. I've never had a real problem with stragglers on my gravely, but i use a kubota machine on one property and if i lift the deck up a little too high i get ton's of stragglers. I've never checked to see how close those blades come together though.
  5. Auroris

    Auroris LawnSite Member
    Posts: 155

    If you look at your eMark Metro 36" from the front, the left blade is not only forward of the right, but does overlap (unless I am horribly mistaken), doesn't it?

    One way to tell would be to take the mower out into the lawn, engage the blades without moving forward, now disengage blades. Now move the mower and see what kind of pattern is left in the lawn?

    I'd like to know if you get a chance to try it since the 36" Metro HP is one I'm loooking to buy.
  6. greenman

    greenman LawnSite Addict
    Posts: 1,405

    How can they overlap when the baffles for the mulch kit enclose each blade? They dont overlap. I have hit a bump in a lawn many times and it makes the deck bounce, leaving swirls. Two circles. Not oval.:confused:
  7. CMerLand

    CMerLand LawnSite Senior Member
    Posts: 393

    Yes they overlap and precisely because of what Auroris said.

    Because the blades are not on a parallel plane to the direction of travel. This is the case with a walker mower and why they require timed blades. IF they were not timed they would hit each other in the middle.

    However, with a 36 and with the 48 inch mowers because the blades are not parallel to the front of the mower there is a slight overlap.

    Simple experiment. Take out two quarters. Draw two lines at 90 degree angles to one another to form a T.

    Next, put one quarter on each side of the bottom leg of the T. When they are both an equal distance from the top of the T, they are configured like a walker.

    Now move the right quarter slightly up and to the left so it crosses over the center of the T-line. Thats how your blades are configured and why you have an overlap. Still the same size quarter but because of the small shift up and to the left you have an overlap.
  8. TLS

    TLS LawnSite Fanatic
    Posts: 7,940


    I really can't believe this has been posted.

    I know I'm up late (just got in from the garage) but I really cant beleive I'm reading this.

    There are a few (very few) mowers out there that have "timed" decks. Where each blade spindle is keyed, and the blades interlace or "overlap". One example of this is a Walker deck. Some other manufacturers have used timed decks. My Aunt and Uncle had a mid 80's cheapie tractor w/ a 44" deck that had two big blades and a cogged belt. My Aunt hit a big rock and skipped a few cogs. Boy did that make short work of two blades.

    All, and I mean just about all other decks have some sort of offset to the spindles. John Deere DOES have one of the biggest offsets out there, Hustler is another one.
  9. Phishook

    Phishook LawnSite Bronze Member
    Posts: 1,143

    It's just MAGIC !

    Or is a wounder of nature?

    My question is, Where do the clippings go from inner blades? The right side blade on my GD has an exit place for the grass to go out, but the other two blades don't!:confused:
  10. hubb

    hubb LawnSite Member
    Posts: 192

    LOL Phishook!
    I agree with TLS. I can't believe more owner/operators don't get the basic concept their machines work on. This is too funny:D

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