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  1. #1
    Platinum Member TNhobbyfarmer's Avatar
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    Middle Tennessee
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    Kubota 3430 4WD

    Default How often do you sharpen/replace blades on you rotary cutter?

    I was bush hogging yesterday. Seat time give you lots of time to think. I got to thinking about my blades and how often I should either sharpen or replace them. I thought I would come to the TBN brain trust for opinions.

    I'll give you my thoughts/opinions. You give me yours. The blades on a rotary cutter are not intended to be sharp. In fact they come new with a 1/16 or so edge. The cutting isn't dependent on sharpness but rather the shear force behind those large rapidly spinning heavy objects. So bottom line, I don't worry too much about real regular maintenance. As long as they are not just beat to h***, they seem to work just fine. Just my 2 cents. Now hopefully some of you guys who are much smarter than me will chime in.
    Jerry
    Kubota L3430 with FEL

  2. #2
    Platinum Member TNhobbyfarmer's Avatar
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    Middle Tennessee
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    Kubota 3430 4WD

    Default Re: How often do you sharpen/replace blades on you rotary cutter?

    Oops. That should have been your not you in the title of the thread. It wouldn't let me edit the title.
    Jerry
    Kubota L3430 with FEL

  3. #3
    Elite Member Baby Grand's Avatar
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    Windsor, CT.
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    Kubotas: L3240GST B2320HST B5100D & G5200H

    Default Re: How often do you sharpen/replace blades on you rotary cutter?

    I agree, in principle. My suspicion is that the blades "cut" by kinetic effect, rather than shear action. Similar to the way a kinetic anti-tank round works. They just beat the h*** out of what ever they encounter, unless it's too tough, and then they just beat to h*** out of the operator. I had a real wakey-wakey moment encountering an old engine block in a thicket of multi-flora rose.

    The modern KE weapon (rotary cutter) maximizes KE and minimizes the area over which it is delivered by:
    being fired (operated) with a very high muzzle velocity (blade tip velocity)
    concentrating the force in a small impact area (that 1/16" edge) while still retaining a relatively large mass (blade)
    maximizing the mass of whatever -albeit small - volume is occupied by the projectile (blade), that is, using the densest metals practical, which is one of the reasons depleted uranium is often used.
    Just substitute (my words) into the text, and I think it reads about right for a rotary cutter. Except for the DU bit.
    That's the problem with trouble.
    It always starts out as such fun."
    - Randall Brown

  4. #4
    Member
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    Dec 2010
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    31
    Location
    Shawano WI
    Tractor
    NH Workmaster 55

    Default Re: How often do you sharpen/replace blades on you rotary cutter?

    I agree that sharpening to a razor edge is not worthwile, but I try to put some kind of edge on my rotary blades at the beginning of the season.

  5. #5
    Gold Member TerryR's Avatar
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    Boone, NC
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    JD 870

    Default Re: How often do you sharpen/replace blades on you rotary cutter?

    After 8 to 10 years of no attention, I finally took mine off and sharpened them, as best I could given the tough shape they were in. Then two years later I bought new blades, and have tried very hard to keep them out of the rocks. I find that sharper blades cut cleaner, and work the tractor less.

    Terry

  6. #6
    Veteran Member Marveltone's Avatar
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    Somewhere north of Roseau, MN
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    Fordson Major Diesel, McCormick Deering W4, Ford 1510, John Deere L111

    Default Re: How often do you sharpen/replace blades on you rotary cutter?

    So far, I've just let the beat-up, blunt edge do the bashing without being sharpened. It shatters the stubs of saplings into relatively soft, frayed brushes sticking up into the air, rather than sharpened punji sticks. So far, I haven't had one puncture my rather delicate turf tires. I'd like to keep it that way. Besides, I'm also under the suspicion that frayed, shattered stubs decompose faster than sharply cut, intact ones.

    I suspect when the time comes when it no longer cuts (shreds?) the grass and just starts laying it down, I may pull out the grinder and restore the blades back to the original 1/16" edge. Until then, I'll just keep hacking away as is.

    Joe
    Joe

    Fordson Major Diesel: Case 3-bottom Trip Plow, Case 12' Trip Field Cultivator, Kewanee 130 Disc, John Deere 1209 Mower Conditioner, John Deere 594LW Side Delivery Rake, New Holland Hayliner 273 Baler, 18' Spike-Tooth Harrow
    Ford 1510: Du-Al 105 Loader, "The Thumb" Grapple, Bush Hog RBC60 Rear Blade, Woods HC54 Rotary Cutter, Tarter 5' Heavy-Duty Hinge Back Box Blade, Buhler Farm King Y600 Snowblower

  7. #7
    Elite Member rekees4300's Avatar
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    Feb 2010
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    Indiana
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    JD 4300, JD X500

    Default Re: How often do you sharpen/replace blades on you rotary cutter?

    Haven't sharpened my bushhog blades in 12 years and still cuts fine. Probably should sharpen them but taking them off, sharpening, balancing, putting back on with proper bolt torque is a major project so will hire the JD dealer to do it.

  8. #8
    Super Star Member
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    Yanceyville, North Carolina
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    Kubota L4400

    Default Re: How often do you sharpen/replace blades on you rotary cutter?

    The PUPIL who does not surpass his Master, fails his Master.

  9. #9
    Veteran Member
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    Jun 2011
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    2,313
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    CNH 4020

    Default Re: How often do you sharpen/replace blades on you rotary cutter?

    Quote Originally Posted by TNhobbyfarmer View Post
    I was bush hogging yesterday. Seat time give you lots of time to think. I got to thinking about my blades and how often I should either sharpen or replace them. I thought I would come to the TBN brain trust for opinions.

    I'll give you my thoughts/opinions. You give me yours. The blades on a rotary cutter are not intended to be sharp. In fact they come new with a 1/16 or so edge. The cutting isn't dependent on sharpness but rather the shear force behind those large rapidly spinning heavy objects. So bottom line, I don't worry too much about real regular maintenance. As long as they are not just beat to h***, they seem to work just fine. Just my 2 cents. Now hopefully some of you guys who are much smarter than me will chime in.
    I agree completely. Mine has 2 heavy swing blades attached to a "stump jumper" center plate. Even the directions say you should not sharpen them.
    They are not intended for mowing yards and have no suction lift.
    Up here we would say: " that's like trying to make a silk purse, out of a sow's ear"
    Not to be saying anything derogatory about a sow's ear. Everything has it's purpose

  10. #10
    Gold Member
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    Jul 2007
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    485
    Location
    Ohio hill country
    Tractor
    2006 TC45A

    Default Re: How often do you sharpen/replace blades on you rotary cutter?

    My BH is 7 years old, I do 10 acres and noticed this year the cut was getting kinda lousey. Don't really want to take them off. Will probably sharpen them as per the article posted above or have the dealer do them.

    Mine take 600ft lbs to tighten and my torque wrench does not go that high and I don't want them coming loose and killing someone.
    2006 TC45A

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