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  1. #1
    Silver Member
    Join Date
    Jul 2006
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    109
    Location
    Kalama,WA
    Tractor
    Kubota B7510HSD

    Default How and when to sharpen Rotary BH blades

    I have a bush hog that I bought a short time ago. My land is mostly 15 degree or better slopes and the terrain is quite uneven. To be safe, I mow up and down the slopes. Actually because of some of the terrain I can't always tell if it's up or sideway because it's deceptive I find that a lot of time I'm englfed in dust. Even if I raise it, if I want to cut weeds and tall grass the brush hog will bottom out and hit dirt. There's a few small rocks but not a bunch.

    My question is, how do you know when it's time to sharpen the blades and how do you do it. I looked at the blades when I got it and it just looked like flat stock. what am I missing?

    Harris
    Kubota B7510HST, FEL, tooth bar, brush cutter, box blade, portable forks, tiller, boom pole, carry all, homemade 15" bucket mounted dirt scoop.

  2. #2
    Epic Contributor Bird's Avatar
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    Mar 2000
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    37,619
    Location
    Texas

    Default Re: How and when to sharpen Rotary BH blades

    If you use the search function, you should find lots of previous discussions on the topic of sharpening brush hog or rotary cutter blades. Most manuals say to leave approximately a 1/8" flat edge on them instead of making them sharp as you would with a lawn mower or finish mower. That's because they are made to cut (or shatter) woody type material (brush, bushes, or saplings) and a razor edge would very quickly have nicks in it. Of course if all you're cutting with yours is grass, you can certainly sharpen it to a finer edge to get a neater, cleaner cut.

    As for how to sharpen it? Some sharpen the blades with an angle grinder without removing the blades from the machine. Others remove the blades and sharpen them on a bench grinder or put them in a vise and sharpen them with an angle grinder. I've tried all three of those methods and don't know that I have a preference, but of course, I had an air impact wrench to remove blades. If you don't have big enough or strong enough wrenches to remove the blades, then the angle grinder is the way to go.
    Bird

  3. #3
    Gold Member
    Join Date
    Dec 2003
    Posts
    444
    Location
    Emporia, Kansas
    Tractor
    Kubota L3130 HST

    Default Re: How and when to sharpen Rotary BH blades

    Hoist that puppy way up in the air and get your angle grinder out and grind away. It's the simplest and fastest way.
    If you try and take the blades off, you'll get frustrated VERY quickly....

  4. #4
    Super Member Farmwithjunk's Avatar
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    Aug 2005
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    7,514
    Location
    Mt Washington, Kentucky
    Tractor
    Where do I begin.....

    Default Re: How and when to sharpen Rotary BH blades

    Quote Originally Posted by hz293
    I have a bush hog that I bought a short time ago. My land is mostly 15 degree or better slopes and the terrain is quite uneven. To be safe, I mow up and down the slopes. Actually because of some of the terrain I can't always tell if it's up or sideway because it's deceptive I find that a lot of time I'm englfed in dust. Even if I raise it, if I want to cut weeds and tall grass the brush hog will bottom out and hit dirt. There's a few small rocks but not a bunch.

    My question is, how do you know when it's time to sharpen the blades and how do you do it. I looked at the blades when I got it and it just looked like flat stock. what am I missing?

    Harris
    When? When they need it. Actually, it's best to touch them up periodically BEFORE they really HAVE to be ground. It's easier that way and you don't have to suffer through poor results mowing until the baldes are too far gone.

    I usually sharpen 3 or 4 times a summer. That translates to around 15 to 20 hours of mowing between touch-ups.

    How? In 35+ years, I've removed ONE set of blades to grind. It's unneccisary and time consuming. I raise the mower as far as the 3-point will lift it, then back the tail wheel up onto my trailerto support it. I block the front end with jack stands or wood blocks. Even then, I don't actually get UNDER the mower. I don't want to be a statistic.

    4" angle grinder and a face shield. Don't grind the edge at too abrupt of an angle nor too flat. 55% seems to work well for me, although I usually just "eyeball" the angle. Any nicks or rolled edge that sticks below the cutting edge, I grind off flat before working the cutting angle. Then I grind just enough to clean up the edge. They don't need to be like a surgical scalpel. Slightly blunt edge does a sufficient job. Too sharp cuts brush rather than shattering it. That leaves tire killers. Too sharp also doesn't hold an edge for long in dirt,rocks, brush and all the other assorted gremlins a bush hog gets into. I try for 1/16th" at the absolute sharpest, and prefer around 1/8th" blunt edge.
    There are three kinds of men;
    1.) The ones that learn by reading
    2.) The few who learn by observation
    3.) The rest of them have to pee on the electric fence for themselves.

  5. #5
    Elite Member
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    Jul 2006
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    3,015
    Location
    midwest
    Tractor
    JD 4520, Toolcat 5610, Bobcat S300, Case-IH 125 Pro, Case-IH 245, IH 1086, IH 806

    Default Re: How and when to sharpen Rotary BH blades

    I may be alone on this one, but I have never sharpened bush hog type mower blades. I figure they are for a rough cut and I usually hit rocks, limbs and so on. My 6' mower is probably 20 years old. Heck, I never look under the thing unless something wrapped around the blades. Maybe that is where Jimmy Hoffa is? I bought is used 10 years ago for $250 but have changed the gear box oil and grease it regularly. Just mowed down probably 100 cedar trees, some 5'-6' tall two weeks ago but went very slow over the big ones.
    Finish mower blades are a totally different story. 3-4 times per year.

  6. #6
    Bronze Member
    Join Date
    Mar 2006
    Posts
    77
    Location
    North Alabama
    Tractor
    Kubota L4630

    Default Re: How and when to sharpen Rotary BH blades

    Factory recommends my blades get sharpened to 1/16" at the edge (Rhino SE6) I check them every few hours and only felt I had to sharpen once (after maybe 20 hrs of cutting). I raise the rig up, put concrete blocks under the edges so I don't get surprised and use a 4" angle grinder, takes about 20 sec of touch up per blade and it's done.

    Total time from when I shut off the tractor to when I turn it back on again is around 5 min or so.

  7. #7
    Veteran Member have_blue's Avatar
    Join Date
    Oct 2003
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    1,730
    Location
    Eunice, Louisiana
    Tractor
    L4400

    Default Re: How and when to sharpen Rotary BH blades

    Quote Originally Posted by radman1
    I may be alone on this one, but I have never sharpened bush hog type mower blades. I figure they are for a rough cut and I usually hit rocks, limbs and so on. 3-4 times per year.

    Agreed! A brush hog used as intended doesn't benefit much from sharpening at all. Heavy brush, rocks, and dirt piles will only undo a sharp edge in 30 minutes.

    Problem is, when you hog your rough stuff and remove your rocks, you end up with a nice grass field. Instead of buying a finishing mower, I kept using my brush hog, trying to make it mow like a finishing mower. In my case, it helps a lot to keep the blades sharp. It's like daylight and dark. Sharp blades do a 200% better job, and require a lot less power. I keep my blades dead sharp, and do a 15 minute touchup before each use. Reducing the PTO RPM just a bit keeps the blades sharp 2x longer.
    -

    Bob

    From the heart of Cajun Country

  8. #8
    New Member wetrombley's Avatar
    Join Date
    May 2009
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    1
    Location
    Magnolia, KY
    Tractor
    Mahindra 3510

    Default Re: How and when to sharpen Rotary BH blades

    I have a similar situation with my 6 ft. bush hog blades. Over the past two years I've noticed that they just are not cutting as cleanly as I would like. I would like to sharpen the blades in place and wondered how difficult it would be with an angle grinder. Since my tractor is a Mahindra 3510, I want to get all the cutting action I can without sapping the horsepower.
    Regards, Wayne

  9. #9
    Super Star Member J_J's Avatar
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    Sep 2003
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    17,222
    Location
    JACKSONVILLE, FL
    Tractor
    Power-Trac 1445, KUBOTA B-9200HST

    Default Re: How and when to sharpen Rotary BH blades

    Quote Originally Posted by wetrombley View Post
    I have a similar situation with my 6 ft. bush hog blades. Over the past two years I've noticed that they just are not cutting as cleanly as I would like. I would like to sharpen the blades in place and wondered how difficult it would be with an angle grinder. Since my tractor is a Mahindra 3510, I want to get all the cutting action I can without sapping the horsepower.
    It is not difficult at all. Just raise it up, support it, and go to work on the blades. They don't need to be real sharp. Don't even crawl under there, just reach in with the grinder.

    If you have the stuff to remove the blades, do so, and sharpen. Impact wrench, 1 1/2 socket, or whatever. There is a hole in the top plate with a cover. just for this.
    J.J.

    When I works, I works hard. When I sits and thinks, I goes to sleep.

    Git er done.

  10. #10
    Platinum Member
    Join Date
    Jan 2009
    Posts
    965

    Default Re: How and when to sharpen Rotary BH blades

    Got a 5 ft kk cutter that has 7-8 years on it just cutting grass and weeds,very little brush,no rocks,etc. Still does a fine job cutting, never sharpened blades.

    Figured,[if mower still is workin when they do need some attention] would just take torch,cut bolts off,and put new blades on,seems the simplist thing to me to do.

    Always sharpen my own lawn mower blades[got an old sears mower that I have shapened probably 10 times,same blades] so not worried about doing it,just figured to sharpen them right,would need to take them off hog,and if I was going to go through that probably painfull procedure,would just cut bolts off and put new blades on,than I'd be good for another 10 year??!!

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