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Rotary mower blade sharpening thoughts.

blade sharpening

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#1 MiCarl ONLINE  

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Posted July 25, 2016 - 01:26 PM

I've got a little down time today and decided to take advantage of it by sharpening the blades on my new Simplicity ZTR.  They've got half a season on them and I figured it was worth a look.


The blades didn't have any nicks in them but the edges weren't what I'd consider sharp.  The cutting edges seemed rounded and not as sharp as your typical butter knife.


I ground the blades so the angle goes all the way to the cutting edge.


I started looking on line for blades because I'd like to go ahead and have another set on hand.  I noticed in one of the pictures the new blade seemed to be no sharper than mine were when I removed them.


My previous mower had a mulching deck and the curvature of the blades made them difficult to sharpen.  Since I had access to aftermarket replacements at wholesale cost (under $6 each) I always just replaced rather than sharpening.  Those blades were always as sharp as I just made my Simplicity blades.


So I searched the internet for articles on lawnmower blade sharpening.  Most of the articles say the blade should only be butter knife sharp.  I understand why they shouldn't be ground to have a razor edge, but "butter knife" sure seems too dull to me.


Did I over-sharpen my blades?


What do you folks do?

Edited by MiCarl, July 25, 2016 - 01:33 PM.

#2 Bill 76 ONLINE  

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Posted July 25, 2016 - 03:23 PM

I always sharpen mine the same way you do- sharp but not razor sharp , sharp enough to cut me.They probably don't stay that sharp for long but that's always how I have done mine.

Maybe I've been it wrong all these years but will keep doing it that way until I, am proved wrong. 

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#3 boyscout862 OFFLINE  

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Posted July 25, 2016 - 04:02 PM

I get mine almost sharp. Be sure to balance them. Good Luck, Rick

#4 Cat385B OFFLINE  

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Posted July 25, 2016 - 04:03 PM

My thought was always that I'm trying to cut the grass, not knock it over with enough speed to snap it.

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#5 Bruce Dorsi OFFLINE  

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Posted July 25, 2016 - 04:06 PM

I sharpened thousands of blades in my Dad's mower shop over the years.


Our customers expected to get a very sharp edge, so that's what we gave them.  ...I sharpen my own blades the same way.


In actual use, that sharp edge will disappear after very little mowing.  ...Sandy soils, or cutting close, will accelerate dulling of that sharp edge.


The sharpness of the blade is not as critical as having a nice continuous angle.  ....Hitting rocks upsets that continuous angle.


Having said that, obviously there comes a point where the edge is so blunt that the grass is not sheared, but bludgeoned.

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#6 lrhredjb OFFLINE  



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Posted July 25, 2016 - 05:05 PM

I make mine sharp using a double cut file and it works for me. My lawn is not that good and there are some tough weeds in it.

#7 Gtractor ONLINE  


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Posted July 25, 2016 - 06:02 PM

I try to make mine very sharp but I've seen really dull rounded blades give a very good quality cut over the years so figure its not all that important.

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#8 MiCarl ONLINE  

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Posted July 25, 2016 - 06:27 PM

Well, I just finished mowing.  I can't say the lawn looks any different than the last time I mowed so maybe having a keen edge isn't that critical.


Of course it's been so dry the lawn is going to look like crap no matter what........

#9 chieffan OFFLINE  

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Posted July 25, 2016 - 06:36 PM

A sharp blade will not pull as hard as dull blades.  If your mowing a lot, less fuel usage with sharp blades.

Edited by chieffan, July 25, 2016 - 06:36 PM.

#10 shorty ONLINE  



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Posted July 25, 2016 - 08:52 PM

The grass always looks better with a sharp blade. The sharper a blade is, the cut edge of a blade of grass is less likely to turn brown. Mine are never as good as I would like tho.

#11 DennyIN ONLINE  

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Posted July 25, 2016 - 09:22 PM

I sharpen them sharp then break the sharp edge with a file so the sharp edge doesn't roll over when mowing. I think the sharp blade is part of it, the other part is having a clean deck so the grass throws better with no or little clumping. I remove and clean the bottom of my deck with a high pressure washer and then spray it down with WD-40 to displace moisture and minimize sticking until the WD-40 wears off.   

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#12 Eric ONLINE  

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Posted July 25, 2016 - 10:59 PM

Depends on blade speed, landscaper friend tells me low speed deck has to have very constant edge and fairly sharp not split hair sharp as that will just alter the constant edge quicker. High speed deck is less critical but the cut angle must be steeper as the cutting action is more of a chop which he says leaves a more consistent cut in thicker grass. Just what I was told but his logic seems sound.

#13 FrozenInTime OFFLINE  

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Posted July 28, 2016 - 04:29 PM

I used to sharpen mine almost every time I mowed.  I mow bout 3 acres.  My soil is sandy, when I sharpen as needed, I go through 2, sometimes 3 sets of blades.  When I don't sharpen, 1 set lasts a season.  At close to $100 per set of 3, I have stopped sharpening so much.  Yard still looks ok with dull blade but yes, sharp blades will put less stress on grass and it grows nicer looking.  IMHO