How and when to sharpen Rotary BH blades

[cisco]

Lots of prior posts on this issue, like most others. In brief, rough cutting requires little in the way of blade sharpening unless one has really rocky soil, lots of raised stumps or similar. For finer cutting, grinding out major nicks in the blade edge, and narrowing such to the 1/8 - 1/16 inch range, is preferable (examine the cut end of the grass before and after you sharpen the blade, and note the ease with which your tractor/hog combination runs). I change blades every few years, for a large field grass area my wife likes to see "nice", keeping the last used set for rougher stuff, like thick brush, saplings and such. I sharpen the blades every month in about 15 minutes - time to raise cutter as high as 3pt will allow, place blocks under the cutter, put on a faceshield and use an angle grinder. Every 6 months or so I drop the blades off with a 3/4" impact wrench (my 1/2 inch was not up to the task - it's a 1 & 13/16 nut), and use the bench grinder. .......And if all I did was cut thick brush, and my wife wasn't looking over shoulder, I might pay a lot less attention to the blades. That said, putting a bit of an edge on a rotary cutter blade is EASY.

 

[sld]

If you are going to go to the trouble of sharpening them I would take them off and do it right.

You really should attempt to balance them, even if it is just hanging them on a nail. I can tell when mine are slightly out of balance but maybe that is just because I have a smaller tractor.

I like to feel the smoothness in a beast like a bush hog.

 

[PM1]

I've never tried sharpening my blades with an angle grinder while still mounted, but it sounds easier than removing and reinstalling blades. The bottom edge of the blade is flat, and the top edge is beveled. How do you grind the top beveled edge (and see what you're doing) with the blades still mounted?

 

[skipmarcy]

I've never tried sharpening my blades with an angle grinder while still mounted, but it sounds easier than removing and reinstalling blades. The bottom edge of the blade is flat, and the top edge is beveled. How do you grind the top beveled edge (and see what you're doing) with the blades still mounted?

It's the way I've always done it - it's ridiculous to R&R blades for a sharpening. As far as balancing them - I've been sharpening the set on mine now 3 or 4 times a year for about 8 years and have never had a balance problem. Touching-up the edge with an angle grinder might take 1/4 oz. to 1/2 oz. of metal off - not much affect on a blade that weighs about 10 or 15 lbs. I just bring the 3 point up as high as it will go and shorten the toplink and the rear of my cutter is right at eye level while sitting on a small crate. I clamp a pair of vise-grips to the end of the blade I'm working on and let it butt up against the cutter housing to hold it still. Plenty of room between the deck and blade for my 4 1/2" grinder. I guess if you have a rear guard of some sort you would have to remove it but mine doesn't have anything. I can touch my blades up in less than 5 minutes and get a nice cut on my yard.

 

[LoneCowboy]

It's a rotary cutter, not a finish mower.
If you want a perfect cut, get a finish mower.

rotary cutters (aka bush hogs) don't cut, they shred. (I like that in Texas they call them shredders, it's a much better name). Look at the tip of the grass blade that gets cut, it's literally torn apart, not sliced clean like a mower. Sharpening doesn't do boo.

90% or more of the cutting happens on the far tip of the blade. When that tip gets worn back an inch or so at a 45 degree angle, you aren't hitting the grass/weeds with a straight edge and the grass slides off instead of being hit at 90 degrees. When that happens, it's time to replace the blade because it won't cut well, it's just bends it over.

There is no sharpening. The cutting isn't happening at the "edge", it's happening at the far tip of the blade, where it's spinning the fastest.

When that tip wears down, buy a new blade and replace.
For us it's every 500 to a 1000 acres.

 

[J_J]

The reason that people sharpened bush hog blades, is that they do want a better cut. When you get a new bush hog and cut a field with out a lot of debris, it does a very good job, and as the blades wear from use, it does start to tear and shred the grass. You could even use a flat faced blade, and it would cut better than a rounded off blade. Some people say they never sharpen, but to each his own. You won't get into balance problems unless you grind more off one blade than the other. Most of the blades start off with a slight edge to them. You all should know by now that a sharp blade cuts better, in any situation. When to sharpen, is your choice. I have even thought of welding some hard surface on the first 2 in of the blade, to reduce wear. It should work.

 

[Deadman]

Its so much easier to just take the blades off, and clamp them in a vice.

 

[J_J]

Its so much easier to just take the blades off, and clamp them in a vice.

What you say is true, but a lot of people do not have air, or a big enough socket, or the torque necessary to take off the bolts.

 

[jb62901]

Took my blades off the other day and did a touch up on them. Weighed them, one at 8.000 and the other at 8.005 think Im good to go this time around. Used a floor jack to reinstall, worked like a champ.

 

[pitt_md]

The reason that people sharpened bush hog blades, is that they do want a better cut. When you get a new bush hog and cut a field with out a lot of debris, it does a very good job, and as the blades wear from use, it does start to tear and shred the grass. You could even use a flat faced blade, and it would cut better than a rounded off blade. Some people say they never sharpen, but to each his own. You won't get into balance problems unless you grind more off one blade than the other. Most of the blades start off with a slight edge to them. You all should know by now that a sharp blade cuts better, in any situation. When to sharpen, is your choice. I have even thought of welding some hard surface on the first 2 in of the blade, to reduce wear. It should work.

I agree with the above. I don't know that it makes a difference when wading through thick brush but I can tell you it makes a lot better cut on tall grass/clover when sharp. It still is not a "finish" quality cut but its pretty darn good.
If it didn't matter if the blades are sharp or not why do the new ones come with a sharp edge?