I sharpen mower blades to a near knife sharpness

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I always see that you should not sharpen mower blades "razor" sharp because they will dull quickly and are more susceptible to nicks.

I believe mower blades do not come really sharp because of liability reasons. Can you imagine the amount of people that would cut their hands changing blades if blades were actually sharp from the factory?

I sharpen mine to a fairly sharp edge and wear cut resistant gloves to install them.

Now hear me out, the sharp blades, if they do dull quickly, will reach an equilibrium where they will reach a close equivalent to a blade sharpened to a dull edge.

Now I will say a highly sharpened blade will nick easier in some cases, however this is not always the case in my experience because I have nicked plenty of blades shaprened to a dull edge.

I bring this up because I put a new unsharpened set on last night because I had hit a piece of metal by the road and really nicked one, and I did not have time to sharpen the new ones. Well I noticed they were tearing the grass, and the cut was just not as good as when I use a highly sharpened blade.

Just Sayin.....
 
Can you explain why a machete has the same profile as a lawnmower blade?
 
There can be no argument you get a better cut with your SHARP blades, the question would be how long does that cut last? Do you change the profile of the bevel or spend more time getting the factory angle sharp? Bet your lawn looks really nice the first few cuts.
 
I hit a couple small rocks that the mower mulched up. Naturally it was just after I sharpened the blades. That blade got nicked up so bad it looked like a serated knife and didn't cut worth a [censored]. I almost couldn't save that blade.
 
Why put in all the extra time & effort to achieve razor sharpness to have it disappear in 1/100th of the time it took to sharpen the blade? Waste of time and effort no?

The coarse grass, weeds & gravel out where I cut grass would dull that edge in about 30 seconds.
 
Wouldn't razor sharpness roll over real fast?

Don't get me wrong....I'm all for sharp cutting tools but something like a mower blade needs to be sharpened with longevity in mind.
Small twigs and such nicking a blade are inevitable.

If your lawn is "perfect" or you're doing established gold courses etc., you can go surgically sharp.

Also, dressing a blade frequently is probably what carefully maintained outdoor cutting equipment needs.
 
Originally Posted By: eljefino
Can you explain why a machete has the same profile as a lawnmower blade?


generally nobody cares about the cleanliness of a cut with a machete.

People may in some cases care a bit more about the lawn.

Reel mowers do a better job anyway...
 
I have been sharpening blades for my OPE customers for 40+ years, and always sharpen them to a very sharp edge. I agree that in general they will dull faster, although there are some customers that have very nice lawns, and take care to not hit anything but grass, and after a full season of use they bring the blade to me to resharpen, and it is still very sharp. But The average customer wants to see it VERY sharp when he takes it home. I sharpen a LOT of blades.
 
Originally Posted By: JHZR2
Originally Posted By: eljefino
Can you explain why a machete has the same profile as a lawnmower blade?


generally nobody cares about the cleanliness of a cut with a machete.

People may in some cases care a bit more about the lawn.

Reel mowers do a better job anyway...


A few years back we did a stadium tour of Minute Maid Park (Astros) … the grounds keepers were mowing and they brought one over. He had a John Deere reel mower with a basket … blades so sharp they were cutting 1/16” with a clean cut …
 
My OEM JD blades come from the factory with a 1/64 inch edge sharpness. The blades have two angles leading to the blade sharp edge. A steep angle to just before the final edge. I think this allows a sharp blade that lasts long. Ed
 
My mower blades have been heat treated. It is very difficult to sharpen without overheating them and making them soft. I have blued a blade and that spot got dull very fast. I have set up my grinder with a compressed air hose and blow lots of air over the point of cut. This keeps the blade cool and preserves the temper.

Rod
 
I’ve had some custom mower type blades made by an OEM and I think blades aren’t razor sharp because it would take more time (=cost) to make them that sharp in a market where a dollar makes a difference. All of the machining is done pre-heat treatment. A refined edge would have to go back through the sharpening sequence.
The company asked how sharp and for my application it was as sharp as they can get them. The blades were sharper than a standard mower blade but not knife edge sharp.
 
Originally Posted By: AZjeff
There can be no argument you get a better cut with your SHARP blades, the question would be how long does that cut last? Do you change the profile of the bevel or spend more time getting the factory angle sharp? Bet your lawn looks really nice the first few cuts.


This^^

I've done the ultra sharp edge thing, easy with any stone on any tool and it does yield a really clean cut for maybe three hours of mowing. After that, it's gone.
 
It's a matter of how often you wish to sharpen. A really sharp blade cuts well but dulls fast. I grind mine sharp but not knife sharp. I have 3 sets for the zero turn. A mulch gator set for spring/ fall leaves. 2 sets of regular toro blades for summer. That way i always have a sharp set. I take my time sharpening them, as i don't want to get them hot and lose the hardening.
 
I sharpen mine to knife edge, but I use hand tools, so heat is not a concern. My lawn is a 2 minute mow, so it lasts plenty long.
 
I don't even bother. The blades that can be bought for my mower are WAY too soft. After one season they're toast. I try not to hit stones but the soil is sandy in some areas. On our old John Deere the blades that came from the dealer were hard steel. I used them for 4-5 years before they were toast. I don't get it.
 
Originally Posted By: SEMI_287
I don't even bother. The blades that can be bought for my mower are WAY too soft. After one season they're toast. I try not to hit stones but the soil is sandy in some areas. On our old John Deere the blades that came from the dealer were hard steel. I used them for 4-5 years before they were toast. I don't get it.


Just put a new blade on the old Craftsman 22” … $7 off a clearance rack so that’s how I sharpened … grabbed two that will fit the 42” in a week or two … $20 for that set and being I will pull the deck ~ may as well do the 7 year old belts …
 
I have 7 acres and a pull behind finish mower with three blades. I've never been able to grind blades properly to get them really sharp. About the best I can do is knock off the rounded edge; no fear of nicking my finger, but the yard does look better afterwards. Probably time to get new blades as they are 10 years old now. New ones seem to run about $60 or more.
 
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I sharpen the full blade, and balance it. I have been doing this for 30 years. Just makes sense. I see a far better cut when I tested this 30 years ago with long grass and 2 new blades sharpened the same , but one a full length sharped blade.
 
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