There are a few reasons for the "dull" blades. The flat edge provides two cutting edges. A very sharp blade quickly dulls anyway. Homeowners are cutting their hands by installing razor sharp blades. Just some of the reasons I've heard. I don't think you'll ever notice the difference in cut.

Rick, no the blades should not be sharpened. Just put 'em on (making darn sure that they're right side up) and go like heck!

*I don't think you'll ever notice the difference in cut."...I have to agree with this. I have a mower with a blade I have sharpened once in 8 years and even then I just dressed it up a little with a file. I didn't notice any difference before and after. However, if you are anal about blade sharpening no one will stop you.

Yes, I think the urge to sharpen rotary mower blades is largely a carryover from the time when reel mowers were the dominant design. The two cutting surfaces had to be aligned and properly finished to function. Old habits get passed down through generations of mower owners whether they are relevant or not.

The slight benefits of rotary blade sharpening are probably a visual inspection if blade integrity and assuring the blade is still in balance.

you can sharpen all you want, but it you mow in sandy or dry conditions with the deck low the blades will take sand blasting. Higher you cut your grass the longer the blades will last IMO.

Blades will dull then after years or months of use in the right conditions they will shapen themselfs. Usually the tips are very worn and the metal is worn thin at the end shaped like C. I touch mine up about every 4 weeks, rebalance, in my conditions due to the sand and dry conditions. My conditions usually the blade ends or tips wear causing me to replace the blades within year or two.

I just have to say that a sharp or better yet "properly finished" blade will give your grass a much better cut. If you cant not tell the difference between an old worn out blade and a newly "finished" blade/brand new blade either you just arent paying attention/looking at your grass or you dont know how to "finish" a blade properly.

A dull/worn out blade will leave ragged edges on the cut grass. This is is very hard for the grass to recuperate from and can lead to an unhealthy lawn. If your blade is in proper repair, your grass should have a perfectly straight edge and not be ragged in the slightest.

I dont look at my blade to tell if I need to run a file across it, I look at my grass.

Somehow I missed the part where someone said that an old worn-out blade would perform as well as a sharpened one. I had the impression that the discussion was about using a new Gator blade just as it came from the factory, or sharpening it. I will agree that a sharpened blade will do a better job than the old worn-out blade that bsmith introduced into the discussion.

"I dont look at my blade to tell if I need to run a file across it, I look at my grass." Good work if you can get it. Personally, I'm not that discerning. Tho, I've gotten strange looks when I tell someone their blade was installed upside down and they didn't know the difference. On repairs, I sharpen to about .015 if they are on the machine and if they end up in the customer's hand nice and razor sharp like they want to see them...

Whell, when my old blade finally wore out and broke I just made my own by bolting an extra piece of rebar to the motor, and it cuts and runs just like the day I bought it.

From reading this I see who really cares about their grass.
The sharper the blade the better the grass will look. Yes, the sharper cut is a cleaner cut and less chance of getting a fungus.
The mower will also run easier.
Now if you hit rocks that will damage your blade, but if you are a home owner you should have removed the rocks a long time ago.
I have seen people put their blade upside down by mistake and still cut grass. I have also seen that they can overheat the engine by making this mistake.
Having a extra set of blades is the way to go .
Also using a flat file can really do a good job.
Remember the blade cuts mostly at the tip. So, a dull tip is a dull blade.
Anyway, I always keep my blades sharp. And painting the spare blades keeps the rust off.

Backing up what Brandon and a few others have implied... first off, yup, you not need to look at the blade of the mower, but rather the tip of the blade of grass will tell all! Like an idiot light on a car, if ya notice that the grass is lighter brown on the top in color all of a sudden like, and the water table is still up, then look closer to the tip of grass blade.... if it is brown past just over the very top of the tip, then your blade needs sharpening.... if the grass blade is split, then you are very much damaging your lawn.... my ears are nowhere's near what they could be, but the first thing I hear with a new blade cutting is this cool sound... it just plumb makes a cool sound... you can hear it like a samari sword lol... leave the grass length up with good water tables, and follow it down in height while the dry out comes, then follow it back up during fall season... cut consistently... one way in direction one time, the other way next time, on borders, then stripe out... different angle of stripes each cut, and if ya can use a different size mower each other time... ok, that part is rather extreme, but all of these things are to prevent sway.... and striping, while also looking good, is also a economical bonus... closest distance between two points is... a straight line! simple math, good practices, and some experience and common sense will have your lawn looking it's finest Cheers!

Anyone who believes cutting with a dull blade produces a quality cut must have had his swing set up too close to the garage eve,s ! RC , we have the same grass and cutting conditions apparently lol.

"From reading this I see who really cares about their grass.
The sharper the blade the better the grass will look. Yes, the sharper cut is a cleaner cut and less chance of getting a fungus.
The mower will also run easier.
Now if you hit rocks that will damage your blade, but if you are a home owner you should have removed the rocks a long time ago.
I have seen people put their blade upside down by mistake and still cut
grass. I have also seen that they can overheat the engine by making this
mistake.
Having a extra set of blades is the way to go .
Also using a flat file can really do a good job.
Remember the blade cuts mostly at the tip. So, a dull tip is a dull blade.
Anyway, I always keep my blades sharp. And painting the spare blades keeps the rust off."

Agree with everything said here. The only thing I can add is that good blade balance and tracking keeps vibration down.

I mulch and have 3 blades on my rider. There is a huge difference on the load being placed on my mower, plus the mulch gets chopped finer and dissapears better. I use a combo sander with its adjustable rests because I can keep a consistent angle and chew less metal. The sander works great for my chipper, post hole digger and other blades as well.