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How can I sharpen an 8" tri-arc brush cutter blade?

Discussion in 'Chainsaw' started by cbr929rr, Jun 14, 2007.

  1. cbr929rr

    cbr929rr ArboristSite Member

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    Just purchased my ryobi 30cc brushcutter ( expand it model ) and all sides of the 8" tri-arc blade are blunt.
    *Can I sharpen, grind, or file the sides like a lawn mower blade to get better performance?
    *Which edges should be sharpened, ex. the insides or outer or both edges?
    *Has anyone done a muffler mod to this line of ryobi tools?
    *Is there anything else that will help this machine cut any better?
    I know this is a homeowner model and not meant to perform like profesional models costing 3x as much. Thanks for any help...
     
  2. computeruser

    computeruser Addicted to ArboristSite

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    File away, from both the top and bottom, like a knife. Start the sharpening up near the hub and work all the way to the tip. The Stihl tri-blades come that way, and I'd figure that most other quality ones would, too. You can do both the leading and trailing edges, too, assuming the blade is symetrical; that way you can just flip it over and have a sharp edge to keep working with.

    Out of curiosity what sort of stuff are you cutting and how is that machine working out so far? I ask because I recently picked up a used Stihl FS200 (36cc, 2.2hp) that I converted to a brushcutter. Piston and cylinder are pristine, and after replacing the carb and working out an early fuel delivery gremlin, it seems happy as can be with woody material up to .75" and with care and patience the tri-blade was OK in 1.25" ailanthus. Haven't yet tried the chisel tooth or four-edge grass blades that I also bought.

    Happy brushcutting!
     
  3. Lakeside53

    Lakeside53 Stihl Wrenching

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    Just don't make it too "sharp"... It's supposed to be "blunt".
     
  4. Crofter

    Crofter Addicted to ArboristSite

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    Two cautions about muffler modding. The design is made to limit rpms to a safe number so you dont blow up any cutter heads. Some of the Ryobi/MTD designs have fixed jet carbs and some have limited range of adjustment so if you do much modding you could have problems. I have modded and played with a few of these for Radio Control airplanes. The older Pre EPA ones had full adjustable carbs.
     
  5. blis

    blis Addicted to ArboristSite

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    I fail to see how you could make it too sharp...
     
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  6. Lakeside53

    Lakeside53 Stihl Wrenching

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    It blunts to easily if "too sharp" and edges break off. Look at the factory sharpen...it's just a little less than a 1mm "edge". We're not talking wood saw blades or clearing blades here...
     
  7. Stihl #1

    Stihl #1 ArboristSite Operative

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    When the brush knife is sharpened, a guide, part number 4020 890 5500 is available. Use it to be sure that the blade has the same amount of material removed from each of the three cutting surfaces, and that the proper angle is maintained. The gauge is set and then rotated to each tooth to verify they are even.
    I attached a pic, and will try to insert, I just never seem to get it right. Maybe this time.
    [​IMG]
     

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