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View Full Version : How to sharpen your mower blades?


BAMARED
06-26-2001, 10:03 AM
I've been using a simple file and sometimes a bench-mounted grinder. Is there other easier, faster ways?

Thank You,

Steve Parsons

TGCummings
06-26-2001, 10:19 AM
Steve,

I would recommend a dedicated rotary blade grinder (RBG). I picked one up several weeks back, due to recommendations on this Board, and it's a thing of beauty.

Do a Search on Blade Sharpening for more information!

-TGC

Wangel
06-26-2001, 10:20 AM
There are a few ways to sharpen mower blades.

1) Drill attachment either on or off the mower.
2) Belt sander
3) File
4) Sharpening stone(s)

I have always felt that if the blade just needs touching up, then you can do this on the machine. But, if the blade has many deep knicks, twists, etc. then it is best to remove blade, sharpen, and then balance.

I prefer to have an extra set of blades so that I can just switch them and continue to run.

The blade edge is something I've heard differing opinions on. Some appear to like a razor edge, claiming that they can cut faster, and the grass looks better. Granted, the edge does seem to go away faster. Others prefer, what I like to call the scissor edge. I've seen some people who will use the razor edge blades on one type of lawn and grass and then switch blades for other types.

awm
06-26-2001, 02:20 PM
i totally agree with previous post. i will say this if you cutting with a fast ztr,you need as sharp as you can get it.

SMB
06-26-2001, 05:43 PM
4 ½" Craftsman Pro. angle grinder, the only complaint I have is it heats up the blades really quickly with about 10,000 RPMs.

Administrator
06-26-2001, 06:10 PM
Gotta recommend the MAG-9000 Series Blade Sharpener from Magna-Matic.

This is a TRUE blade sharpener. Not just a fancy bench grinder. :)

http://www.magna-matic.com/products/sharpeners/mag9000.html

BTW... I also sell this sharpener so if your interested let me know.

Chuck K

David Gretzmier
06-27-2001, 12:55 AM
we use a 4 1/2 angle grinder, I wish I had the 9" industrial dewalt grinder that a big shop here uses. 2 licks and that baby is sharp. alot of folks here use the rbg or magnamatic. good luck... Dave g

lawnMaster5000
06-27-2001, 01:51 AM
i have been looking for a dedicated blade sharpener, i am sick of using the competion's (used to work for him). I was wondering if anyone has other brands other than magna-matic, and if its any cheaper than about $550. I think thats alot, but i guess so is everything else. thats why we charge alot.

thanks

David Haggerty
06-27-2001, 08:23 AM
I'm with the people who use the 4 1/2" grinder. I have a 9" Milwaukee hand held grinder but it's too hard to control. Every bench mounted grinder I've ever tried just turned the blade blue. If they're blue, you're loosing the temper of the blade.
I mounted a vise a little lower than my waist. I wear goggles and an apron. Hold the grinder with two hands with arms propped against my body for stability. Position the blade so you can send a rooster tail of sparks to the ceiling. Keep the grinder moving side to side. The blade should come out silver, right down to the cutting edge. Balance it with a $2 cone-on-a-stick type balancer. Only sharpen one side. Grind until you see no sign of wear on the bottom of the blade. That shiny surface on the bottom should be completely gone. Follow the rounded off contour right around the edge. If you get the edge perfect, but it's not balanced, grind a little off of the back edge.
It's fast, inexpensive and gives a very good edge. Practice on some old blades. You'll get the hang of it.
Dave

Holloway Lawns
06-27-2001, 12:56 PM
I take mine to a local small eng repair guy he charges 5 to sharpen and balance on a blade sharpener it works for me those machines are to high for me to justifie buying one right now.

TJLC
06-27-2001, 07:44 PM
I bought an old used RBG for about $65.00. Once you use it for a while and get the hang of it, you probally wouldn't want to use anything else.

Green Hands
08-27-2009, 12:31 AM
I use a small hand held 4 inch grinder but instead of using a grinding stone I use the grinding disk composed of layered sand paper. It is cheap and does not take off too much blade or heat it up hot. The wheel is blue and looks like heavy sandpaper. I buy them at Home Depot for about $6 bucks.

STIHL GUY
08-27-2009, 12:36 AM
i use a bench grinder and a blade ballancer

Lbilawncare
08-27-2009, 01:07 AM
$5 a blade adds up. I love my Magna-Matic. Overlook the cost, because if you buy a decent dedicated unit it will last virtually forever.

Kutz Lawns
08-27-2009, 03:00 AM
A Ryobi 4 1/2 angle grinder is about $29 from Home Depot, put the blade up on a small table or hose caddy and just hold the blade with your foot and grind away to razor sharp, it doesn't get any easier or cheaper!

I sharpen mine before I go out everyday & if your doing 3 to 4 high end thick fescue lawns a day, their dull!

Kutz Lawns
08-27-2009, 03:04 AM
$5 a blade adds up. I love my Magna-Matic. Overlook the cost, because if you buy a decent dedicated unit it will last virtually forever.

He's probably talking once a month or every other month at $5 a pop!

THC
08-27-2009, 03:15 AM
i totally agree with previous post. i will say this if you cutting with a fast ztr,you need as sharp as you can get it.

How come people say DO NOT make them too sharp, that they will last longer?

This is so counter intuitive to me, I ALWAYS make them as sharp as razors but cutting is still never as (almost never) easy as I would like.

John deer Z
08-27-2009, 08:05 AM
I have a angle vise and use a 7 inch hand held grinder.The angle vise alows you to put what ever angle you want from 0-90 degrees. I then touch up the edge with a file to get burs off.

Still cutting 75-80 yards a week I change them 1 time a week.

Mowbizz
08-27-2009, 07:10 PM
How come people say DO NOT make them too sharp, that they will last longer?

This is so counter intuitive to me, I ALWAYS make them as sharp as razors but cutting is still never as (almost never) easy as I would like.


Well you don't understand the "science" behind a lawn mower blade's sharpness.
A razor edge will dull within a few minutes of mowing...while a blade sharpened then filed a bit to leave a slight flatness to the edge will hold that edge longer than the razor sharp edge. The way blades come from the factory is what you should attempt to emulate while re-sharpening. The angle of the edge is as important as the sharpness as well. The manufacturers of blades have, sometime in the last millenium, have figured out what the best edge to mow with is...the factory edge!
( I could explain this till blue in the face, and some just will never get it)

Richard Martin
08-27-2009, 08:47 PM
You mean like Mowbizz?

http://i208.photobucket.com/albums/bb56/RMartin631/mower%20stuff/DSC00651.jpg

E & J Pro Turf
08-27-2009, 10:39 PM
Long live this thread it was started in 2001. I love it.............................

Mowbizz
08-27-2009, 10:56 PM
You mean like Mowbizz?

http://i208.photobucket.com/albums/bb56/RMartin631/mower%20stuff/DSC00651.jpg




What the heck is that picture supposed to be showing?
:dizzy:

Mowbizz
08-27-2009, 10:58 PM
Long live this thread it was started in 2001. I love it.............................

Oops...didn't notice that...this site should not keep posts older than 1 year. That's crazy:dizzy:

Richard Martin
08-28-2009, 07:23 AM
What the heck is that picture supposed to be showing?
:dizzy:

If you look at the edge of the blade you'll see I flattened it off. I've been doing that for years. :)

Mowbizz
08-28-2009, 09:23 AM
If you look at the edge of the blade you'll see I flattened it off. I've been doing that for years. :)


OH...can't really see that in your pic...:drinkup:

GravelyNut
08-28-2009, 09:55 AM
If you look at the edge of the blade you'll see I flattened it off. I've been doing that for years. :)The blades for the 50" deck on the Gravely that are carbide inserts come that way from the factory. They still cut great. Despite what most people would think, it's the speed of the blade and a square edge that does the job.

And for those who turn their blades blue when grinding, where's the bucket of water for cooling the blade? If you can't touch it due to the heat, it needs cooled.

Grass Cake
08-28-2009, 11:12 AM
this subject tilts me so hard

if the last 1-2" of the blade truly did all the work,blades would be made with a 1-2" grind

give me a blade with a center to end grind and i'll cut circles around you,+ it'll be 10x cleaner

theres more than just lopping off grass when it comes to blades
also
blunting the edge is ridic, its like cutting rope with a dull pocket knife,you'll cut it






eventually
/rant

milike
08-28-2009, 01:31 PM
4" angle grinder most of the time...

sometimes a bench grinder if I have alot.

Richard Martin
08-28-2009, 03:51 PM
blunting the edge is ridic, its like cutting rope with a dull pocket knife,you'll cut it eventually

You should try it before you knock it. The edge of that 90 degree angle stays sharp for a while. I've been cutting grass commercially since 1994 and sharpening blades this way is the best I've ever found.

gunsworth
08-28-2009, 10:34 PM
You mean like Mowbizz?

http://i208.photobucket.com/albums/bb56/RMartin631/mower%20stuff/DSC00651.jpg

I supposed bending them helps too :laugh:

Doc Pete
08-28-2009, 11:30 PM
blunting the edge is ridic
/rant

YUP......................
If you don't care about the tips of the grass turning brown, why sharpen at all.
The funny thing is, the important part is the correct grinding wheel hardness..............
Too soft, you waste the wheel in minutes. Too hard, the wheel burns and doesn't cut.........

Richard Martin
08-29-2009, 06:05 AM
I supposed bending them helps too :laugh:

It's a brand new Oregon blade. Take it up with them.

YUP......................
If you don't care about the tips of the grass turning brown, why sharpen at all.

The tips of the grass don't turn brown smart guy. :nono: It cuts the grass clean and stays sharper far longer and requires less passes through the blade grinder to resharpen. Instead of trying to figure out the mechanics of why it shouldn't work why don't you try it and see that it does work?

Doc Pete
08-29-2009, 08:56 AM
The tips of the grass don't turn brown smart guy. :nono: It cuts the grass clean and stays sharper far longer and requires less passes through the blade grinder to resharpen. Instead of trying to figure out the mechanics of why it shouldn't work why don't you try it and see that it does work?

Ah, I knew there was a reason why I stopped posting here.........Thanks for the advice, "O most wise one".

Richard Martin
08-29-2009, 09:55 AM
Ah, I knew there was a reason why I stopped posting here.........Thanks for the advice, "O most wise one".

I'm not trying be a "O most wise one". I share a technique I use to sharpen blades and people shoot it straight down without even trying it. Whatever. I've used razor sharp blades before. They were really great for the 10 minutes that they're razor sharp. Then they're no longer razor sharp.

Doc Pete
08-29-2009, 12:23 PM
I share a technique I use to sharpen blades and people shoot it straight down without even trying it.

As due I share the fact that there's a world of different in grinding wheels...........
In addition there's also a difference between commercial cutting and 5 million dollar home owner lawns:)
Finally, I remember you with great ideas... and forgiving. :usflag:Keep in mind, if the blade cuts better with a 90 degree edge, then why put any bevel on at all. Just have a straight blade with a sharp edge.

Richard Martin
08-29-2009, 01:39 PM
Finally, I remember you with great ideas... and forgiving. :usflag:

I'm still that way. But it gets old after a while when no matter what anybody posts there's always someone there to criticize the post. A month or so ago I started a thread about a mower that I put brakes on. The very first reply was an obvious smart assed answer. Yeah, I could have just bought a mower with brakes but they cost twice as much and we actually had a lot of fun putting the brakes together. I come here to help my few lawn men and to keep up to date on the new goings on. You never know, there might be someone else with the same mower as I have and they can easily see how to put brakes on it. I gave a detailed description of the work involved and included pics. Earlier today there was a new thread that wasn't getting any replies and had been up for a while. I went in there and gave my theory as to a possible answer and that was criticized multiple times. Give it a rest people. We're here to work together. I may come off as a jerk sometimes but you can't keep punching on me and expect me not to punch back. I am only human.

Kutz Lawns
08-29-2009, 01:52 PM
It's just like ass***es, everybody's got one!

Just shapen YOUR blades the way YOU like them, damn!

Richard Martin
08-29-2009, 02:39 PM
Keep in mind, if the blade cuts better with a 90 degree edge, then why put any bevel on at all. Just have a straight blade with a sharp edge.

That's actually a good question and one that an engineering or physics department can only answer. Now just give me a second here.....

We keep trying to apply a slow speed, slicing type theory to this grass cutting. After all, we know that in order to cut a piece of steak or a rope you need a sharp knife. But you can't just push on the knife and expect it to go through the steak or rope very far if at all. You must move the knife back and forth in a slicing motion to get through the material.

But we don't cut grass slow or with a slicing motion. It's cut at a relatively high speed with a striking motion.

Additionally, if you look at things on a molecular level, which is where cutting occurs at, even a surgically sharp knife is tearing and ripping through the material that it's going through. It has to pull one molecule away from another to seperate or cut a material. It's basically the same thing as driving a log splitter into a log.

I don't believe it really makes a difference when both edges are sharp. Whether it's a 90° angle or a sharp edge. I think the only difference between the 2 is how long that angle or edge can be maintained before "cutting" performance is degraded.

But without the benefit of a engineering or physics department we will just have to never know the answer.

Kutz Lawns
08-29-2009, 02:59 PM
ANYTHING spinning around that fast is going to cut or thrash something!

A string trimmer is the same principle, just spinning nylon, it's not even sharp & it's just spinning around fast enough to slice or tear though it!

The sharper the blade only makes the difference of the cutting edge of the grass blade, either cut nicely or torn off!

Damn, this is not rocket science!

Grass Cake
08-29-2009, 03:13 PM
I'm not trying be a "O most wise one". I share a technique I use to sharpen blades and people shoot it straight down without even trying it. Whatever. I've used razor sharp blades before. They were really great for the 10 minutes that they're razor sharp. Then they're no longer razor sharp.

i find just the opposite.......ymmv

I may come off as a jerk sometimes but you can't keep punching on me and expect me not to punch back. I am only human.

we're all human, i'm no physicist but, the blade sharpening is something we all deal with ( some better than others ....punch :) ) it flat out stinks when you get to a job site and realize you muffed the grinding up the day before because you were tired/hungry/hurrying.

btw...i spent 40 bucks on my blade setup. i know for a fact this machine has been grinding "stuff" for 35+ yrs as i took things to this very (cool old) man when i was in my teens.

i changed nothing...the motor/wheel are not aligned,the frame is flimsy,it has a 1/4 hp motor that hums along after weathering who knows what. It'll sharpen both ends of a blade( razor sharp) in about 3 minutes tops!

another side effect: the dip before the sail always wore thru while the edge still had a lil grinding material left. not so when the edge is razor sharp everyday!

It's my belief that the grass folding over the blade causes the wear and the sharper the edge the less folding occurs...again ymmv

thx for your opinion/technique tho
i could be completely out to lunch on this.....but me thinks not :)

http://i295.photobucket.com/albums/mm134/VDownSwingV/grindnwheel.jpg

bigjim56
08-29-2009, 03:44 PM
Just to add my $.02. Being a newbie I have yet to get a ZTR, but I will and I figure I will try the blade sharpening idea mentioned here by Rich Martin before I pass judgement. I figure a few cuts with the factory sharpened blade and on the first sharpening project I can try the squared edge. After closely checking the "cut" I will then judge. what have I got to lose, I'll be mowing this lawn for years from now. I want to find out what works and what does'nt work as soon as I can.

Rich Martin...at what width of a blocked edge do you use? Have you tried varying thicknesses?

bigjim56

AStout
08-29-2009, 04:52 PM
I haven't been at this a long time, but from my initial observations I believe Richard is probably correct. I know it is counter intuitive but let me see if I can share some insight into what is going on here.

When I bought my new ZTR I noticed the "new" blades were not very sharp. I used them for some time and had purchased an extra set when I bought the mower to make blade sharpening something I could do without having down time mowing. I.e., sharpen the old set while the new set is out mowing.

I took the first blade set off after about 25 hours of mowing because I had been into some terrible stuff including gravel, crushed concrete, iron rebarb and many many very hard limbs, etc. I was surprised at how good of shape they were still in despite all the abuse.

Regardless I was thinkning like most here and thought that a really sharp edge would cut better and last longer, so I hand sharpened the other new set of blades before putting them on the mower. After only about 10 hours on the new "sharp" set I felt it wasn't cutting as well as it should and I pulled them off to take a look. Even though I had hit far less hard items the blades looked much worse than the first set that I had installed that were original "factory sharp".

I then saw threads like this and someone mentioned that one of the manufacturers recommended the blunting of the blade after reaching a sharp edge. I didn't "get" it at first but after considering this I have the following theory. I actually think that the most probable ideal situation would be if the blade is ground at the original 30 degree angle until sharp and then finished at about 85 degrees for the final edge to the 1/32 to 1/16 thick "edge" that was recommended by one of the manufactures. My manufacturer made no recommendation in this regard and only stated that the blades should be sharpened only by a "professional".

From what I saw between the original blades and the hand sharpened ones is that the "sharp" ones had far more serious "dents" in the edge. I believe this is because the very sharp edge has extremely little strength to stand up to impact with things other than a blade of grass and at least in the type of mowing I do there is a lot of that. I beleive that the "blunt" or thicker edge offers far more strength at the point of impact and is less dulled by contact with things harder than grass itself.

You then ask why not just have a 90 degree blade at full blade thickness and I believe that is because then the blunt edge is too wide and would then tend to bend the blade of grass over, rather than ripping through it. You could make the blade very thin, but then it would not have the strength not to bend constantly every time you hit something hard.

So cut Richard some slack. I belive there is merit to what he is recommending and it seems to match my observations. I don't have a lot of commercial mowing experience, but I actually do have a significant background in physics, mathematics and science and a very keen understanding of how things break and how things operate at the micro level. I have made a living repairing large scale computers and all the devices that are used with them, going back to the days when they were large beasts and had many electo mechanical parts and pieces. The best thing I had going for me was a very keen ability to observe and make solid conclusions. I believe that the thin but squared off or sharply angled edge cuts just as well as the extremely thin "sharp" edge and keeps its shape much longer, thus being a more effective sharpening technique. You will note that most scissors have this high angle edge at the cutting point and do the job very well. They are not ground to a very thin edge. The same is true of cutting shears for hair, etc.

It's like he said. Maybe you should actually try it before condemming it as "ridiculous".

Richard Martin
08-29-2009, 04:57 PM
Rich Martin...at what width of a blocked edge do you use? Have you tried varying thicknesses?

The recommended is 1/32" to 1/16". I've never tried anything thicker than that.

Grass Cake
08-29-2009, 05:41 PM
I
It's like he said. Maybe you should actually try it before condemming it as "ridiculous".

we should try shaving with scissors :rolling eyes

of course a blunt edge has more strength, its more mass

that doesn't lead us to a cleaner cut

/rant x2

btw: i tried it every way till Sunday,including having them professionally sharpened <- what a joke

AStout
08-30-2009, 12:17 AM
we should try shaving with scissors :rolling eyes

Right, and comparing cutting grass mixed with dirt, sand, twigs, gravel, etc. with a piece of steel moving 18,000+ feet per second has anything at all to do with shaving your face with a blade... Now that is ridiculous! :rolleyes:

Good luck with your blades and this post...

chuacro
08-30-2009, 01:02 AM
I would like too say I appreciate your information on this site. I try it and do not like it I go on to something different. I am glad that you are not a cheerleader for a commercial site.

Runner
08-30-2009, 01:24 AM
Right, and comparing cutting grass mixed with dirt, sand, twigs, gravel, etc. with a piece of steel moving 18,000+ feet per second has anything at all to do with shaving your face with a blade... Now that is ridiculous! :rolleyes:

Good luck with your blades and this post...

Wow! 18,000+ feet per second? That's about 12,000 mph. That's pretty fast! :drinkup:

AStout
08-30-2009, 12:28 PM
Wow! 18,000+ feet per second? That's about 12,000 mph. That's pretty fast!

Sorry, I meant feet per minute... my bad...

The point is the same, cutting grass with a rotating piece of steel in the environment of a yard has about as much in common with shaving your face with a blade as drying your hair with a blow dryer has in common with standing in the middle of an F5 level tornado.

Grass Cake
08-30-2009, 12:35 PM
You will note that most scissors have this high angle edge at the cutting point and do the job very well. They are not ground to a very thin edge. The same is true of cutting shears for hair, etc.


it was you're analogy!

"ridiculous"


indeed

bigjim56
08-30-2009, 12:52 PM
Richard Martin Quote:

The recommended is 1/32" to 1/16". I've never tried anything thicker than that.

Thanks Richard, I will buy a second set of blades to be ready for the blunt blade trial run upon first blade transition. I will check the original factory stock blades for their sharpness before the first cut.

bigjim56

DiamondLawn
09-10-2009, 04:55 PM
yeah, what's next sharpening the round or square trimmer line