Go BottomPuzzled by blade edge
 | cutter
Join Date: Feb 2000 Posts: 1307 The South Shore of Lake Ontario, New York 
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2002-06-02 39255
As I have always done, I puchased an extra set of blades for my latest mower to use when the current set requires sharpening. I am a bit puzzled by the Kubota blades. When I removed my deck last week to use the machine for loader work, I noticed the relatively new blades that were on the machine when I bought it seemed dull. Since they had perhaps only twenty hours of mowing on them, that appeared odd to me. I have used blades an entire season and actually found they did not need to be sharpened much. I checked the new blades that were still in the box from Kubota and found them to be not much sharper than the original set. I am wondering if these blades are designed to be run without a knife edge. The dealer could not answer my question so I thought perhaps someone here might know. It seems odd to me they would need sharpening out of the box and the owners manual for the 72" deck states that sharpening is required when the blade appears worn or has struck something. It says nothing about sharp edges. I do know my bush hog rotary cutter blade is meant to be dull, but I don't think I want my lawn to be torn rather than cut. Any help would be appreciated. Thanks.
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 | Peters
Join Date: Feb 2002 Posts: 3034 Northern AL 
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2002-06-02 39259
I found the same thing with the Bulher I bought last year. I think the blades are left dull until they are installed or finished shipping so that someone does not get cut on the sharp blades.
I have never seen a razor sharp axe or machette at a store either. Although for splitting you don't want it sharp axe. ....
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 | DavidJ
Join Date: Jul 2003 Posts: 62 Alabama 
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2002-06-03 39273
My JD mower blades are not meant to be sharpened in the conventional sense about 1/16 of the bottom edge is left square instead of sharp. It's supposed to make the edge last longer. It looks kind of like the depiction below. They cut well and when I sharpen them I maintain that shape.
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| cutter
Join Date: Feb 2000 Posts: 1307 The South Shore of Lake Ontario, New York
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2002-06-03 39276
David, that is how mine look. It would be nice if a Kubota expert (Art) was available to add his comments! Mine seem to cut nice as well but I thought perhaps it might be damaging the grass with that blunt spot. ....
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| Spring Valley
Join Date: Jul 2003 Posts: 7 Terre Haute, Indiana
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2002-06-30 39931
As a commercial lawn mower, I sharpen the blades on my JD mower every 10-12 hours of mowing. I put a sharp edge on the blade that would cut your finger. I even sharpen new blades before I put them on because they have the flat spot on them. You do not want the grass to tear, you want it to cut. Besides, sharpening often will require you to take off less material to get your edge back.
Remember, sharpen often and make them sharp!!
Matt ....
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| cutter
Join Date: Feb 2000 Posts: 1307 The South Shore of Lake Ontario, New York
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2002-06-30 39938
Oddly enough, the replacement set from Kubota is about a quarter inch narrower than the original set and the blade is cut at a single angle, although not extremely sharp. I put the file to them last week and changed them out. When I removed the OEM's that had been on since the end of last summer, I was able to get a better look at the cutting edge. The blade is ground at a slightly lesser angle than the replacements and a second angle is then added in the last eigth of and inch to create somewhat of a blunt cutting edge. The edge would probably last quite awhile, but is never really sharp enough to do a great job. Like you said, sharp is best and there apparently is no way to avoid constantly keeping them that way. I had thought of trying to put a case hardening on the edge after they were filed, since I rarely strike anything with them but thought better of it due to the cost of another set. Once they are wore down a bit I may try that. I was able to purchase some that way from Gator for my Grasshopper a number of years ago, I never did have to sharpen them. ....
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| Peters
Join Date: Feb 2002 Posts: 3034 Northern AL
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2002-06-30 39939
It seems to me that we talked about this in regards to Brushcutters also.
The old reel mowers slice the grass rather than breaking the end. The better the cut the healthier the grass.
The sharper the blades the less power you will use and the cleaner the cut.
Having hand cut miles of rain forest with a machette I would say it is easier to resharpen a razor sharp blade and not worry about the odd ding from a rock than work with a dull blade.
The main question is how do you get a hard steel with resilience and flexibility.
Many lawn mower manufactures just provide a soft steel blade.
A hardenable grade of tool steel is desired but a blade also needs to be resilient so that it will not split when contacting the odd rock.
Metallurgy like a sword blade, hard and soft layers, would be desirable but it would be difficult to control the process.
As I stated before I think the initial edge is just a matter of shipping and handling. ....
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 | Art White
Join Date: Jan 2000 Posts: 6898 Waterville New York
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2002-07-01 39946
I like my blades sharp when cutting as stated earlier it takes less horsepower and does a better job. Many different edges come from the factory as they all don't come from the same mold. To keep them sharp on the top gives the best cut, the best angle is a little more alusive as the blade design dictates some of this. When sharpening you should do it the same as the manufacturer has made the blade. Sometimes before we get them they are banged up enough that it makes it tough to figure out but any sharp edge is better than no edge at all. Been away to big tractor school in Dallas this past week. Hope to keep up with you folks better this week. ....
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