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

[TNhobbyfarmer]

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.

 

[TNhobbyfarmer]

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

 

[Baby Grand]

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.

 

[mogwai]

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.

 

[TerryR]

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

 

[Marveltone]

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

 

[rekees4300]

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.

 

[creekbend]

How to Sharpen Bush Hog Mower Blades | eHow.com

 

[pacerron]

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

 

[sweep]

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.

 

[sweep]

Even the directions say you should not sharpen them.

My Brush Hog instructions also say not to sharpen them but to replace as needed. My dealer say's he sharpens them properly and does it all the time.

 

[MESSMAKER]

I hit mine with a grinder while still on the machine. It takes about 5 min per blade. I do it about every 25 hours of mowing. Spend more time on the end. That is where most of the cutting takes place. Dull blades may work better in rough stuff. It makes tree stumps less likely to become spears(tough on tires).

 

[k0ua]

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

What he said.

James K0UA

 

[Soundguy]

i sharpen them at the beginning of the season.. and inspect them at the end of the season for cracks or wear that would mean I need to replace them.. that way if needing repalcing i can do it over the winter..

if i hit any noticable or catastrophic debris whilst mowing I reinspect after that session and dress or re-evaluate as needed.

soundguy

 

[Soundguy]

My Brush Hog instructions also say not to sharpen them but to replace as needed. My dealer say's he sharpens them properly and does it all the time.

i think there is a bit of nomenclature issue goin on here.

a hog blade is not 'sharpened' as is a finish mower blade or a lawnmower blade.. rather it is dressed to have a thin blunt edge.. say 1/16 or 1/32 etc. this shatters stubble and prevents making sharp points that puncture tires.. also inhibits plant growth.

 

[Ken45101]

Replace them? The only time I did that is when I had a blade break off.

I've "sharpened" them once or twice in 12 years.

 

[TripleR]

About every three or four years, I touch them up with a 4" angle grinder. I can't say this is what should be done, just what I do.

 

[Western]

I've sharpened one set, using a 5" grinder while still on the shredder. didn't go for "sharp", rather uniformity. I worry about blade balance more than the sharpness, a large nick or other major blow and I would just replace the set (if it felt out of balance). A finish mower (I dont have) would be different as Soundguy said.

I have thought of hard surfacing my blades with 7018 welding rod , but figured it wouldn't be worth the trouble.

 

[jobguy]

I sharpen the blades as I cut a lot of tough grass. By the time I get to the brush they are dull enough that they work well for that job also. As stated above, when the grass lays down instead of being cut, sharpen the blades
I started pulling the brush to keep it from growing back cutting was making things worse (buck-thorne).

 

[DK35vince]

I prefer mine sharp.
I sharpen the blades about once per year with an angle grinder.