# Rotary Mower- Blade Sharpening



## cnet24 (Jul 14, 2017)

Ok, so I know I just disqualified about half of this board by asking a question about rotary mowers (haha), but I'm curious to hear some of your preferred methods to sharpen your blade.

Reason I ask, I went to sharpen both of my blades tonight with this kit from Home Depot, while trying to go the cheap route:

http://www.homedepot.com/p/Arnold-Universal-Lawn-Mower-Blade-Sharpening-Kit-490-850-0006/300615901

I came away very unimpressed. The process took way longer than I expected, the blades didn't come out nearly has sharp as I had hoped, and I burned through almost half of the sharpening stone bit.

How do you keep your blades sharp?


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## J_nick (Jan 28, 2017)

cnet24 said:


> Ok, so I know I just disqualified about half of this board by asking a question about rotary mowers (haha)


Most reel mower owners still own rotary mowers. They make good vacuums :rofl:

I use an angle grinder to get the right profile then use a file to finish the edge.


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## chrismar (May 25, 2017)

I use an angle die grinder with my air compressor. I clamp my blades to a table, bust out the die grinder with a "medium" sanding pad and go to town. I try to match the angle of the existing grind, but I don't stress over it. I grind it down until it's sharp. Takes just a few minutes per blade.

Here are the sanding pads I use:

https://smile.amazon.com/gp/product/B01HZMUNMK/ref=ox_sc_sfl_title_13?ie=UTF8&psc=1&smid=A3FV4MIBE1RGSA


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## dfw_pilot (Jan 28, 2017)

I use a simple bench grinder that's older than I am.


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## g-man (Jun 15, 2017)

I use a 1in flat file.


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## cnet24 (Jul 14, 2017)

J_nick said:


> cnet24 said:
> 
> 
> > Ok, so I know I just disqualified about half of this board by asking a question about rotary mowers (haha)
> ...


Haha, that's one way to keep the rotary in commission once you make the switch. Which I can say, I have the itch now to get a reel since joining this forum :shock:

Thanks for the info.



chrismar said:


> I use an angle die grinder with my air compressor. I clamp my blades to a table, bust out the die grinder with a "medium" sanding pad and go to town. I try to match the angle of the existing grind, but I don't stress over it. I grind it down until it's sharp. Takes just a few minutes per blade.
> 
> Here are the sanding pads I use:
> 
> https://smile.amazon.com/gp/product/B01HZMUNMK/ref=ox_sc_sfl_title_13?ie=UTF8&psc=1&smid=A3FV4MIBE1RGSA


Awesome, thanks for the link. If you use a rotary as your main mower, what's the lowest setting you are willing to go to cut?


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## chrismar (May 25, 2017)

cnet24 said:


> Awesome, thanks for the link. If you use a rotary as your main mower, what's the lowest setting you are willing to go to cut?


I'm a cool season guy with a commercial walk behind mower. Changing heights on it is a royal b*tch, so I try not to adjust it unless I absolutely have to. For me, that usually means about twice a year: 3" for fall and spring, 4" for summer.


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## J_nick (Jan 28, 2017)

cnet24 said:


> ....what's the lowest setting you are willing to go to cut?


As low as possible with Bermuda without scalping it. If you're getting a lot of half moons then go up a notch.


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## cnet24 (Jul 14, 2017)

dfw_pilot said:


> I use a simple bench grinder that's older than I am.


Kind of upset this didn't come with a picture!


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## Overfloater (Jun 5, 2017)

I use an angle grinder with flapper disk. Takes about 30 seconds per blade.


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## RockyMtnLawnNut (Jun 23, 2017)

Angle grinder with flap disc for me too...works great and you can see the angle you're getting on the blade better than with a bench grinder


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## GrassDaddy (Mar 21, 2017)

Angle grinder ($5 at harbor freight) and flap disc (forget the cost but similar)

https://www.youtube.com/watch?v=rXWNon54juw

I found doing it this way to be a lot easier than the bench grinder I previously used. You can follow the angle of the blade much easier because you see the angle. When you use a bench grinder you are kinda guessing because the part you are sharpening is opposite of you.


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## Colonel K0rn (Jul 4, 2017)

I've been sharpening my blades with a die grinder and Roloc discs for years. If you'd like a video demonstration of this method, Wranglerstar has a nice video showing you this method on how to do it this way. I really enjoy watching his videos regardless. This one is about 5 years old. His channel is great.

https://youtu.be/oKvONc59Erg


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## cnet24 (Jul 14, 2017)

Angle grinder and flap disk it is. Appreciate everyone's input!

Grassdaddy- Newly subscribed to the YouTube channel, great work.


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## MasterMech (Sep 24, 2017)

I used to have a proper grinder for rotary blades, did a fantastic job. Sold it with my trailer (was a mobile SE shop) though so it's back to the angle grinder for me. Find a way to prop and hold the grinder steady and you might surprise yourself how well you do. Oh yeah, when it's sharp, I will square the leading edge so instead of a razor point, just so it's about a 1/32" (less than a mm) flat face. Performs more better for longer like that.


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## OutdoorEnvy (Sep 27, 2017)

I hand file. Files really aren't that hard to get the feel for if you just give a little time. Mower blade steels aren't tempered that hard so really any file should bite in fine. OF course a quality one made in USA, Swiss, or Germany will be even better. Follow the flat surface angle the blade already has. You are just cleaning up the edge to bring it back. You can do this with minimal material removal and get a super sharp edge. File into the edge, wear gloves. Hand tools are much more forgiving than power tools.


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## Spammage (Apr 30, 2017)

Overfloater said:


> I use an angle grinder with flapper disk. Takes about 30 seconds per blade.


+1 - although I probably average closer to 34.5 seconds.


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## Still learnin (Sep 9, 2017)

I just recently purchased the Dremel blade sharpening kit, but haven't had a chance to use it. If it doesn't work well, I'll go to the angle grinder. I've always paid $10 and had them sharpened once a year, but now that I'm trying to have a really good yard, I'm trying to learn and keep a sharper blade.


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## Togo (Jun 7, 2017)

As many have said, angle grinder and a flap disc. Takes a couple seconds each side.


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## pennstater2005 (Jul 17, 2017)

dfw_pilot said:


> I use a simple bench grinder that's older than I am.


Same here. Bench grinder. I probably buy new blades sooner than I actually need to.


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## OnyxsLawn (Mar 15, 2018)

Gonna resurrect this old thread as I think its useful this time of year.

I've been a fan of using the angle grinder/flap disk method in the past but my flap disk was worn out and my blade was shredding the grass a bit so I pulled out my new belt sander to see how that would work.

Surprisingly it worked much better than even a new flap disk does. it got the edge very sharp and is very easy to match the original angle of the cutting edge. the rounded part of the belt also makes it really easy to follow the contours of the mulching blade.

Anyone else use this method?


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## SCGrassMan (Dec 17, 2017)

g-man said:


> I use a 1in flat file.


+1. Slower to sharpen, but slower when you make mistakes too


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## MasterMech (Sep 24, 2017)

OnyxsLawn said:


> Gonna resurrect this old thread as I think its useful this time of year.
> 
> I've been a fan of using the angle grinder/flap disk method in the past but my flap disk was worn out and my blade was shredding the grass a bit so I pulled out my new belt sander to see how that would work.
> 
> ...


A long time ago, in a land far, far away, I too used that method with excellent results!


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## gene_stl (Oct 29, 2017)

I think a belt like Onysxlawn is the best way to sharpen a regular high lift blade. It has several advantages. 1) a wide one like in the picture makes it really easy to get the edge straight. 2)Belts make it easier to avoid heat damaging the blades. The sparks you see in videos of grindstone blade sharpening machines are impressive but that is not good for the temper of the steel. (Lawn mower blades are usually "austempered". They work harden in use and that is a good thing generally, unless you hit rocks)3) You can get finer grit belts more easily than you can find finer grit and soft bond grinding wheels. You could change to a finer grit and leave a finer surface on edge.

At my old place I had gotten fairly cavalier about mowing and sharpness. Since it will be a while before my lawn is ready to be reeled I am going to see about putting "fly cutting razors" on the hustler. I recently picked up a belt grinder intended for grinding kitchen and morgue knives. I am going to start on that (it uses two inch wide belts) and finish on a buffing wheel.

I have checked that the original blades from the Hustler aren't bent and I will see how badly I can screw them up. Film at eleven.  :lol:

In the process of researching what others have done I ran across this:
https://www.allamericansharpener.com/?gclid=EAIaIQobChMIkefw2Kjw2gIVRr7ACh0fvAojEAAYASAAEgKVPvD_BwE
The guy makes a $200 jig that should help the accuracy of using an angle grinder. Of course for that price you can buy a nice belt at Harbor Fright. But the guy has worked hard on it and it looks cool.

I have only seen one video where the machine being used pays much attention to the temper of the steel. That is a big expensive automatic machine that has a coolant pump like on a surface grinder. I don't really think that is overkill.


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## g-man (Jun 15, 2017)

I sharpen mine monthly (before the reel). I use the flat file since it is quick and effective.

This video shows the proper way to get a blade sharp using a hand file. How to Sharpen and balance a lawn mower blade


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## zinger565 (Nov 28, 2017)

Reviving this again. How sharp is "sharp enough". Should I be able to accidentally cut myself like I would on a steak knife? Or should it just be sharp enough to grab a bit when I run my thumb over it?


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## g-man (Jun 15, 2017)

I do just like the video above.


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## gene_stl (Oct 29, 2017)

There is a school of thought which MasterMech subscribes to that calls for you to grind sort of a flat on the leading edge.
This is so that there is more meat (steel that is) meeting the grass and especially any rocks or sticks the blade may encounter. I would think you would then have an 80 or 85 degree bevel angle followed by whatever the manufacturer ground. 
I intend to resharpen my three Hustler blades very very sharp and not do the one mm 85 degree bevel thing. I will report back. May take a while. 
But I am of the opinion that since these are what a machinist would call "fly cutter blades" they should be as sharp as possible. The Hustler blades are factory ground at 30 degrees. I am going to go down to 25 degrees and polish the blades.


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## TN Hawkeye (May 7, 2018)

zinger565 said:



> Reviving this again. How sharp is "sharp enough". Should I be able to accidentally cut myself like I would on a steak knife? Or should it just be sharp enough to grab a bit when I run my thumb over it?


When I worked at a local college on the grounds crew we had two different mindsets when it come to sharpening blades: make it like a razor or follow the bevel and make it sharp enough to feel the edge. Without fail, when we would remove the blades to resharpen them the "razor" groups blades would be jagged and have many pits in the edge. The other groups would be dull but still have a solid edge on them. If you remove to much edge by making it razor sharp there isn't enough blade to handle hitting sticks or rocks or other hard objects. Just follow the manufacturers angle and clean up the edge a bit. If you sharpen it razor sharp you'll be throwing away your blade well before you should.


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## Alan (Apr 23, 2017)

I use a $9.99 HF angle grinder...I'm not too concerned with the loss of temper...I'm cutting grass.


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## MatthewinGA (May 21, 2018)

Am I the only one who does a touch-up sharpening before each mow?

Once a year, that would drive me crazy!


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## Alan (Apr 23, 2017)

I usually take a walk around the yard to find anything that may potentially damage the blade before I mow. No rocks, no pine cones(not that they're too damaging), no sticks or logs(ugh!)...then I roll.


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## gene_stl (Oct 29, 2017)

I have started walking the yard too mainly to pick up paper and plastic bags that folks litter. :evil: 
I also pick up heavy branches though I will roll over a pine cone. I only have one pine left so those are gradually disappearing anyway.
I like the idea of a touch up each time! Probably not enough to do it.



> When I worked at a local college on the grounds crew we had two different mindsets when it come to sharpening blades: make it like a razor or follow the bevel and make it sharp enough to feel the edge. Without fail, when we would remove the blades to resharpen them the "razor" groups blades would be jagged and have many pits in the edge. The other groups would be dull but still have a solid edge on them. If you remove to much edge by making it razor sharp there isn't enough blade to handle hitting sticks or rocks or other hard objects. Just follow the manufacturers angle and clean up the edge a bit. If you sharpen it razor sharp you'll be throwing away your blade well before you should.


This makes perfect sense. I don't think I mind sacrificing a little blade life for quality of cut. In one of the videos posted elsewhere about sharpening the guy who makes a blade grinder and probably the best balancer says that the rotary lawn mower blade has the "highest surface feet per minute of any common fly cutting tool" and the tip speed works out to like 10,000 plus feet per minute. For the sake of the grass and the engine I believe the blade should be as sharp as you can reasonably make it. I do see the other idea has plenty of merit too.


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## MasterMech (Sep 24, 2017)

You guys sharpen your rotary blades every time you mow? And I thought there was a lot of work in maintaining sharp reels......


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## Alan (Apr 23, 2017)

I know this thread is old...but...here's my setup.


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## TN Hawkeye (May 7, 2018)

Alan said:


> I know this thread is old...but...here's my setup.


Ditto for mine. I'd eventually like to put a vise on my workbench and sharpen on there but the cinder block works for now.


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## HomerGuy (Jun 5, 2017)

For those of you using flap discs, how long do they last?

I've always used a grinding wheel but grabbed a 40 grit flap disc to try out. I used the flap disc it to sharpen three blades, and this is what it looks like now. I was a little surprised how worn it appears after only three blades.


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## Alan (Apr 23, 2017)

I can't answer your question because it's the first time I've used a flap disc. I too was using a grinding wheel, but felt it was a little too aggressive and not very forgiving so I'm giving the flap disc a whirl. I picked them up at Harbor Freight for $1.99 each w/coupon. If they don't last worth a hoot, I'll go back with the grinding wheel.


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## Garyevans95 (Jun 10, 2019)

I use the Dremel with the sharpening kit. It maintains the right angle, which I don't trust myself to do. Highly recommend.


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