Sharpen a 21' blade

Discussion in 'Homeowner Assistance Forum' started by mlong30, May 13, 2008.

  1. mlong30

    mlong30 LawnSite Member
    Messages: 111

    Hi All,

    What is the best way to sharpen my lawn mower blade? I never done this myself so, I was curious to know what device do I need to purchase to get the best blade sharpener.

  2. lzrj

    lzrj LawnSite Member
    Messages: 245

    I just bought myself a 4 1/2" angle grinder (cheap $10 at Harbor Freight on sale) and grinding wheel for it. I used it the first time over the weekend and was very easy and fast (3 minutes per blade). Used an impact wrench to take off (also bought at Harbor Freight for $30) but you can use a breaker bar as well if the blade is on there good. Just stay at a 30 degree angle (or slightly less) while sharping. You can tell by following the angle already there and watching the fresh metal you are exposing. Sharpen both sides to get a razor sharp blade. Most say don't go that sharp because the sharper it is the quicker it will dull. But I like a the sharpest blade I can get for a smoother more even cut lawn. If you don't have much lawn to cut it will last several cuts. I mow three acres and will probably sharpen between every other mowing. I was nervous at first but once it was done, I felt like a pro and was really easy looking back. One more thing, make sure the blade is balanced when done. If you do same routine for both sides of the blade it should be balanced. All three of my blades were balanced the first time and I did not have to go back a shave a little more off one side to even it.
  3. mlong30

    mlong30 LawnSite Member
    Messages: 111

    How do I kept the blade in a locked position when using the impact wrench?

    Also how do I balance my blade?

  4. Toy2

    Toy2 LawnSite Bronze Member
    Messages: 1,924

    I would just lift the deck with a block of wood and use a Dremel with a grinding stone. I'm sure the blade doesnt need to be balanced.
  5. DavidR

    DavidR LawnSite Member
    Messages: 180

    Ummm...yeah it does kind of need to be balanced. That is a very important part to sharpening. It will destroy your mower if you don't balance the blade.

    As for the sharpening, I use a bench grinder. I have found it works pretty well for my needs. I just try to follow the previous grind as best I can. Just don't get to aggressive of a stone. Do it slowly at first. Also, don't let the metal get to hot as it will start to break down any heat treat that was done.
  6. ffemtmcd

    ffemtmcd LawnSite Senior Member
    Messages: 532

  7. lzrj

    lzrj LawnSite Member
    Messages: 245

    An impact wrench will get the bolt loose just by holding the blade with one hand. Balance the blade by just putting a nail in the wall and putting the center hole on it. If the blade stays even, then it is balanced. If one side falls, that side is heavier and needs to be shaved a bit.
  8. cgaengineer

    cgaengineer LawnSite Fanatic
    Messages: 15,778

    Most important thing to remember is to remove the spark plug wire so that the engine doesnt bump and then the blade cut your hand or arm. Use a block of wood to jam blade and remove the blade. Once blade is removed use a flat file to sharpen blade and keep the file angled at the original angle of the blade edge. When buying a file buy a Nicholson brand, dont skimp on files or you will be unhappy. After sharpening balance blade by using a nail driven into a wall and place center hole of blade onto screw...if the blade stays horizontal its balanced, if vertical remove more metal off the side of the blade that is on the bottom side of the nail
  9. mngrassguy

    mngrassguy LawnSite Silver Member
    Messages: 2,167

    Or just buy a spare blade and switch them. Take the dull blade to your local hardware store/outdoor power equipment dealer. Blades are relatively inexpensive and don't cost much to have sharpened professionally

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