New mower blade

This seems like a silly question... but here goes... I've just purchased new blades for my Craftsman 42" mower. The blades are not at all what I'd call "sharp" - which surprised me. Should new mower blades be sharpened before they are used? or is this angled edge (but again, not "sharp") proper for a mower? If it makes a difference, these are mulching blades.
thanks!
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JaxDawg wrote:

I dunno. It takes a lot less power and noise to cut with sharp blades, at least with my 22" it did. I could run it at low throttle after sharpening where it was full throttle before.
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Ron Hardin
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As a follow-up... I called a local lawn mower place. They tell me that new blades are covered with paint, and that as the paint comes off - the blades will be sharp. Time will tell...
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JaxDawg wrote:

I've been cutting my acre with a scythe for a couple years, and the scythe works on grass only with a razor-sharp edge, which means stopping to resharpen every dozen strokes sometimes, just to indicate how fast an edge wears against grass.
(The stopping doesn't actually slow you down, since it's also a rest, meaning you can work faster when working since a rest is coming up pretty fast periodically)
The sharpness needed on a scythe though is so that half-cut grass doesn't hang up on the edge and form a clot, which I imagine does not bother the nearly-broadside cutting of a mower blade.
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Ron Hardin
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1) How sharp is sharp... kind of hard to say without looking at them.
2) And how sharp do you really need it to be?
A low-angle really sharp edge will nick up and "edge-roll" pretty quick just from hitting grass - so as I understand it, the leading edge on a flat-type mower blade isn't supposed to be knife-sharp. Not rounded, either, though.
I have always found my new blades to be "sharp". And so far, the blade has been a flat end-twisted rectangular blank that has the edge ground onto the steel blank. I can't see how that can be anything but "sharp" as long as the edge is ground onto the blank. (I suppose given a big enough press, one might be able to stamp the edge onto the blank. Then who knows)
FWIW - The edge of the blades on my John Deere have two angles - the cutting edge ground on the main edge is steeper than the other. But only the John Deere dealer has ground them in two angles when re-sharpened.
Hope it helps..

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I was told to never sharpen blades on a lawnmower because it can unbalance it, which would cause other problems. The blades always seem blunt to me when I get a new set, but new ones always cut really well, much better than old blunt ones.
Just give them a go. See how they go.
Jen
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1) Dull blades often go out of balance, especially if nicked. A blade needs to be balanced as well as sharpened, or the blade-shaft bearing will rapidly wear. 2) Dull blades smash the grass into two pieces, rather than cut it, which is hard on the grass; and also the grass looks grey in a day or two.
To balance a mower blade, put the lightly-cleaned-with-sand-paper smoothed hole in the middle of the blade onto a horizontally driven small nail (the blade should not be near the head of the nail, and centered on the hole), or onto a cone-shaped blade balancer. Put the blade horizontally on the nail/balancer, centered on the hole. Grind a bit off the edge on the side that drops. And recheck balance. Repeat until the blade end does not drop more than an inch or so. (or, if klutzy, repeat until the blade has been completely ground away ) )
To double check the setup and balance, flip the blade end-for-end and recheck.

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Surely it would be much safer just to buy new ones. As I said new ones *seem* blunt but cut well. Obviously they are sharpened the way they should be.
Jen
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Ideally the blade for a rotary mower is sharpened to a 30 degree bevel and then blunted by about 1/64" because a razor edge is not durable. In manufacturing if the blades are milled or stamped or milled stamped and hardened the edge burns away to about what you saw on the new blade.
Jen wrote:

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On 29 Sep 2006 05:54:10 -0700, snipped-for-privacy@localnet.com wrote:

My soil is a sandy loam which sandblasts the edge off of mower blades very quickly. Beginning with a sharp edge or not they are quickly blunted.
John

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Jen wrote:

Who told you that? The guy who sells you the new blades?
I bought an extra set of blades for my 42" dual-blade riding mower when I bought it six years ago. I keep the extra set sharpened and ready to go. During mowing season, I swap the blades every month. Takes about 5 minutes. The difference is quite noticeable with freshly sharpened blades.
My lawn is 2.5 acres. The mower has over 180 hours on it. That's 90 hours per set of blades. If I'd bought new blades every time I wanted them sharp, I'd have spent over half the price of the mower already on blades.
Balance? Never had a problem. If the blades are out of balance, you'll hear and feel it. My mower has heavy-duty spindles, and I keep them properly greased.
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I agree with Jen. I have a five year old 48" Xmark with about 320 hours on it from mowing 5 acres. I also swap blades on it and use a dremil tool for sharpening the blades. Balancing has never been a problem. It takes me longer to take the blades off than it does to sharpen them.
I have purchased news blades in the past, some come with a thick coating on the blades to keep them from rusting or from cutting yourself. The first time you more your grass that coating comes off real fast and you should find those blades very sharp.
This is just my opinion and I am no expert on lawn mowers :)
Dan ...........
--
Email "dan lehr at comcast dot net". Text only or goes to trash automatically.

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07:56:58 -0700:

Sorry I'm late on this thread, I don't read r.g all that often.
One thing nobody has pointed out -- mulching blades have several different regions. Some are designed for cutting and some are meant to circulate the air for mulching.
Last time I replaced the blade on my 24" Craftsman (mulching), I noticed the cutting edge was quite a small part of the total blade length, maybe 25%. That would be 3" on each side.
-- spud_demon -at- thundermaker.net The above may not (yet) represent the opinions of my employer.
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Hey John The local mow and go guys seem to feel that the blades with the notched lift wings are more durable in sandy areas. I think one brand is "Gator" JaxDawg wrote:

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