Sharp blades less important when going slower?

Discussion in 'Lawn Mowing' started by Calvin, Jul 9, 2001.

  1. Calvin

    Calvin Banned
    from Ontario
    Posts: 73

    I have never sharpened my blades as much as many members here seem to (once a day, or every second day), usually only once a week or every 2 depending on use. Does the fact that many of you are running z's at high speeds mean that sharp blades are more important.?
    We run WB's (and walk behind them) & 21's on small residentials so we are moving alot slower than a Z in open area. Are razor sharp blades less important in these conditions? Does the blade tip speed compensate for razor sharp blades at slower cutting speed?
     
  2. Eric ELM

    Eric ELM Husband, Father, Friend, Angel
    Posts: 4,831

    I feel that the blades should be sharp no matter if you go slow or fast to help prevent damage to the grass. You can look at a lawn and tell if it has been cut with dull blades or not.

    I change blades daily or more often if I feel it is needed, depending on how fast the grass is growing and how many lawns I have cut in a day. After 10 acres of cutting, they are ready to change since they have lost their razor edge by then.
     
  3. John DiMartino

    John DiMartino LawnSite Silver Member
    Posts: 2,555

    Im with Eric,I see so many guys cut with dull blades,you can see the grass tips torn,and split by them very easiy.A sharp blade leaves a clean cut and the blade of grass is uninjured by comparison.I sharpen every 4-8 cutting hours unless Im cutting low then its more often.
     
  4. carl28

    carl28 LawnSite Member
    Posts: 37

    Our Cardinal Rule when it comes to Blade sharpening is dull blade dead grass. Take the time to Sharpen Your Blades daily. YOur lawns will be the talk of the Town.
     
  5. Kent Lawns

    Kent Lawns LawnSite Senior Member
    from Midwest
    Posts: 870

    Running a Hi-speed Z at 13mph or whatever these guys claim does require sharper blades.

    It's simple physics.

    Does that mean you can run with dull blades? No.
     
  6. rdh

    rdh LawnSite Senior Member
    Posts: 394

    this is what i think ......
    most decks clogg from the wet or damp grass, never in dry grass have i had to scrape a deck.
    ok now lets think about taking a butcher knife and chopping a tomato in half. now think about chopping the tomato with the dull edge. the tomato that was chopped with the sharp edge would have less liquid from the tomato the dull would have more liquid.
    well what im trying to say is that dull blades just beats the liquid out of the grass. the damp grass is what clogs decks so sharp blades not only make grass greener but keeps you from unnecesary deck scraping.



    any comments
     
  7. Kent Lawns

    Kent Lawns LawnSite Senior Member
    from Midwest
    Posts: 870

    I think the mulching/re-cutting charateristics have more to do with the tomato/grass splatter than the knife-edge cut.
     
  8. GroundKprs

    GroundKprs LawnSite Bronze Member
    Posts: 1,969

    Cutting grass with a rotary mower is done by impact, as opposed to the clean scissor action of a reel mower. So if you impact anything with a razor sharp blade, you are most likely making a fairly clean cut; a dull blade makes a ragged cut on anything, if it cuts at all.

    When you are cutting grass, a duller blade will tear the leaves, making them ragged, or shredded. This ragged edge will brown shortly after cutting. I have seen grass blades with up to 1/4" of shredded brown tip from dull blades. Compound this millions of times in a lawn, and you dramatically reduce the green of the lawn. A clean cut will give just a slight brown line on the tip of the grass blade.

    Look at the tips of your grass blades from last weeks mowing, and you can tell if the mower blade was sharp enough. What is often enough to sharpen? At 3", I can sometimes go 2 days, but will still dress the blades twice a day. At 2-1/2", sometimes a blade will last a day. I like my lawns GREEN.
     
  9. Calvin

    Calvin Banned
    from Ontario
    Posts: 73

    Doesn't the fact that the blade is rotating at such a high speed ensure the grass will be cut cleanly even without a razor sharp blade if you are not flying over it with a z but walking behind a WB.?
     
  10. Richard Martin

    Richard Martin LawnSite Fanatic
    Posts: 14,700

    All you need to do Calvin is look at the blades of grass when you are done cutting the grass. If the blades look like the tips were ripped off then you know that it's time to sharpen the mower blades.
     

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