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.
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.
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..
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.
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
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
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
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
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
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.
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 :)
Email "dan lehr at comcast dot net". Text only or goes to trash automatically.
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
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