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View Full Version : Best stone grit for sharpening blades?


CoachLinz
06-20-2003, 10:31 PM
I only have money for a cheap bench grinder for now. I was out looking and there were 2 I saw at a low enough price. 1 has a single 120 grit stone that is approx. 1 1/2" wide. The other has 2 stones - 36 grit and 60 grit - that are each about 3/4" wide. I can buy other stones (coarser or finer) for either one. So ,my question is - what grit is correct for sharpening mower blades? What grit stones are you guys using.

Please don't recommend other, more expensive options. I know there are better machines to do it, but this is all I can afford right now. Next year, I will upgrade.

Grassmechanic
06-20-2003, 11:09 PM
It's been a while since I've sharpened blades (out of the mowing end of the business), but I believe 120 grit is too coarse. I used a ruby wheel, but i forget what grit it was. Hopefully, someone else can help shed light on this.

Mike

CoachLinz
06-20-2003, 11:35 PM
OK. If the 120 is too coarse, then the other 2 are definitely out (lower number=coarser stone). Anybody else know for sure?

TLS
06-20-2003, 11:55 PM
Buy a 4 1/2" hand held angle grinder.

Put blade in vise, clamp down.

And grind away.

Only thing a bench grinder is good for is to put a wire wheel on to clean the blade prior to sharpening and balancing. On the other end I have a fine grit stone to dress the back side of the blade if needed.

If you plan to be in this business, invest in a dedicated blade sharpener. Go out and get a 0% intrest credit card and put it on there!? But you don't want to hear this, right!?


Bottom line, if all you can afford is a $ 75 grinder, get a hand held angle grinder.

grassdaddy
06-21-2003, 12:55 AM
Have you priced blade sharpening in your area?A local hardware store here charges 2.00 each.they do a better job than I can,I have a benchgrinder,4"angle grinder,a dremel tool,a vise and a half dozen files and still can't do a good job. The Lesco dealer does them 3 fo 7.00 and they are fantastic,twice as good as hardware store, 10x better than me.:confused:

Did I mention I'm saving for a good sharpener??;)

TLS
06-21-2003, 12:58 AM
:D

But for $2/blade, Id have them do it too!

Most are $5 to 7 and don't do nearly as good a job as I can.

Navig8r
06-21-2003, 11:48 AM
I use an angle grinder and a big file...... the grinder is only used when the file can't restore the edge...... oh yeah, keep a wire brush handy to clean the file.... makes a big difference.
I have used a blade grinder, and they do work exactly as they're designed to.............. I just can't swing the expense right now.......maybe after some fall clean-up ca$h!.......... ready for next year.

steve225
06-21-2003, 06:23 PM
Use the coarse stone 60 grit.
Steve Snider

Strongmd
06-21-2003, 07:26 PM
I have a magnamatic. LOVE IT!.
I can get a perfect edge in less than 1 minute per blade.
Only way to go. Even a not-so-bright employee can't screw it up.

lawnMaster5000
06-21-2003, 10:56 PM
I am not exactly sure, but i think one of the dealers around here charges homeowners $15 per blade for sharpening.

Again not sure, but can't they buy a new blade for $20?

MOW ED
06-22-2003, 12:20 AM
Sorry bout bein a smart a.. but I can't resist...
this one is gonna go over a lot of the new peoples heads but the old dawgs know what I mean.

If you want grit then you need the Lawrence Stone. or the Larry Flynt..

Thats enuf. Its late and I am leaving now.

hunter
06-22-2003, 01:12 AM
try a 36 grit. Less time to sharpen and keep the blade at a 40 degree angle.

Envy Lawn Service
06-22-2003, 01:24 AM
I don't know what to tell you about the grit. I'm not worth a **** at using grinders. But I grew up in the sticks. So I've sharpened a lot of stuff over the years with a file. After a few minutes and some good old fashioned elbow grease, I can lay a heck of an edge on a blade with a ******* file. I don't know wht grit that would be equal too, but it works well for me. I have one set that has a flatter angle than the others. When I'm finished with those, I have to be careful handleing them. I've cut myself with them twice already.

Doc Pete
06-22-2003, 09:25 AM
Originally posted by CoachLinz
I only have money for a cheap bench grinder for now. I was out looking and there were 2 I saw at a low enough price. 1 has a single 120 grit stone that is approx. 1 1/2" wide. The other has 2 stones - 36 grit and 60 grit - that are each about 3/4" wide. I can buy other stones (coarser or finer) for either one. So ,my question is - what grit is correct for sharpening mower blades? What grit stones are you guys using.

Well, I can see why some guy's don't sharpen their own blades or complain about how long it takes, most of them are stupid. There is only "ONE" grit size......24, got that, 24, not the coarse 36, but 24. OK? That's 24. Gees, just look in the catolog and it will tell you 24 is the best grit. This is a no brainer. Everything else is too fine and too slow. Also, a "Dresser tool" is a must, otherwise the wheels will load up, plus a fresh dressed wheel will cut faster.
Also, with 24 grit there's less chance of heating and burning the blade, and you can sharpen blades in about 2 minutes, with balancing.

hunter
06-22-2003, 03:17 PM
Originally posted by Switchless@aol.com
There is only "ONE" grit size......24, got that, 24, not the coarse 36, but 24. OK? That's 24. Gees, just look in the catolog and it will tell you 24 is the best grit.

Not much differnece between 36 and 24 grit. And 24 is a lot courser than 36. Been using 36 and no problem and that on a 6" grinder. Avaerage blade on takes appox 2-3min and thier done. We all have our own ways right or wrong. Just knows what works for me. That's a big NO brainer. It WORKS.

Doc Pete
06-22-2003, 04:10 PM
Originally posted by hunter
Not much differnece between 36 and 24 grit. And 24 is a lot courser than 36. Been using 36 and no problem and that on a 6" grinder. Avaerage blade on takes appox 2-3min and thier done. We all have our own ways right or wrong. Just knows what works for me. That's a big NO brainer. It WORKS.

As you say 24 "is" a lot coarser than 36. So, I wonder why your #24 stone doesn't cut better than your #36???? For me, the 24 allows a lot more pressure to be applied, taking off more material while also decreasing the possibility of burning.
Pete

steve225
06-22-2003, 08:28 PM
good post Pete.
You're correct more metal less heat the coarser the stone.
Now where can I get a 24 grit stone ?

Envy Lawn Service
06-22-2003, 10:34 PM
To begin, just for the record **** = cr@p and ******* = b@stard as in b@stard file. I didn't know that cr@p and the actual name of a file was considered offensive or whatever :rolleyes:

Anyways, I bought myself a 4 1/2" angle grinder today. I figured I'd try to learn to use one. Is the 24 grit the best to use on it too?

DLCS
06-22-2003, 11:46 PM
Originally posted by Envy Lawn Service
To begin, just for the record **** = cr@p and ******* = b@stard as in b@stard file. I didn't know that cr@p and the actual name of a file was considered offensive or whatever :rolleyes:

Anyways, I bought myself a 4 1/2" angle grinder today. I figured I'd try to learn to use one. Is the 24 grit the best to use on it too?


Don't use a grinding wheel on the angle grinder. You need to get yourself a flap sanding disc. Will not heat the blade up as much and will not remove as much metal.

Envy Lawn Service
06-23-2003, 02:46 AM
Originally posted by DLCS
Don't use a grinding wheel on the angle grinder. You need to get yourself a flap sanding disc. Will not heat the blade up as much and will not remove as much metal.

I have several of those, what grit?

Doc Pete
06-23-2003, 08:13 AM
Originally posted by DLCS
Don't use a grinding wheel on the angle grinder. You need to get yourself a flap sanding disc. Will not heat the blade up as much and will not remove as much metal.

I'll be glad to eat my words, but I can't believe a flap disc will work at all: You can't put enough pressure to cut the steel, or get a sharp edge.............. Please enlighten me..............
Pete

DLCS
06-23-2003, 08:49 AM
Well, all I can say is give it a try. I'm not sure but I think the discs I use are 60 grit. I'll check tonight. You don't need a whole lot of down pressure while sharpening blades.

Likestomow
06-23-2003, 11:00 PM
I have been using Norton's 32A46-KVBE wheels, but I since have tried a 32A60-IVBE and found it to be much superior. It cuts faster and seems to last longer.

Here is a hint: call Norton and ask them to send you a sample to try out before ordering. They have sent me some in the past and should do the same for anyone else.

DLCS
06-23-2003, 11:12 PM
switchless,

I'm not sure if you know what kind of disc that I'm talking about. Here is a link to where you can order them online and they also have a picture. They are on page 2517 of their online catalog. They have many differnet kinds some for steel and some even for stainless.

Craig T
06-24-2003, 07:09 PM
Since my Dad owns a Tool Grind shop and thats what they do is sharpen tools (cutting) and make them I have a little know how on the mower blades. First the bench grinder is fine if thats all you have just be sure to dress the wheels down alittle so they are not to agressive or you will be going through blades like crazy. I use a roller dresser. (Norton wheels) Look up KBC Tools (catalog) they will have all the wheels and supplies you need.
What I use to do my blades is a commercial belt sander with a Baldor motor and different grit belts. It mounts to a bench just like the bench grinder.(Runs vertically) Depending how bad the blades are determines the belt you will want to use. Also with a belt sander you can flex the belt around to get the off-sets of the blades, will make them razor sharp. Just takes some pratice just like the bench grinder. I sharpen my blades once a week and I'm good to go. (exmark excalibur)I will post a picture of the sander in some weeks to come.

saw man
06-24-2003, 07:21 PM
i also use a sander like the guy above, i think you get a better edge than you can with a wheeled grinder.
besides you dont get a hollow grind from a belt sander, so the edge can last longer.

was also in the business of sharpening carbide blades, router bits, etc.

Envy Lawn Service
06-28-2003, 06:46 PM
Originally posted by DLCS
Well, all I can say is give it a try. I'm not sure but I think the discs I use are 60 grit. I'll check tonight. You don't need a whole lot of down pressure while sharpening blades.

I have 40, 60, 80 and 100 grit. I'm going to try them since I'm rained out again.

Envy Lawn Service
06-29-2003, 01:11 AM
I tried the 60 grit sanding disc. I sharpened 2 sets of blades, one of which was a set of Gator blades. I was surprised with the results.

After sharpening the 2 sets, I decided to take off the set on the mower and put a set of these razors on. A few (?) minutes, 2 sets of blades, one set on and 7 small cuts total on my fingers by the time I was done.

Needless to say it was quick and they were SHARP!!!

DLCS, thanks for the sanding disc idea. I would have never thought to try it in a million years.


Now I regret to say that I laid the grinder on the bench as I always do, the sanding disc is much lighter, it tiped off the bench and landed just perfect to snap the disc holder.

:cry: :cry: :cry:

Doc Pete
06-29-2003, 01:18 AM
Originally posted by DLCS
switchless,

I'm not sure if you know what kind of disc that I'm talking about. Here is a link to where you can order them online and they also have a picture. They are on page 2517 of their online catalog. They have many differnet kinds some for steel and some even for stainless.
I don't seem to see the link..... Please post again.
Thanks,
Pete

DLCS
06-29-2003, 01:25 AM
Originally posted by Switchless@aol.com
I don't seem to see the link..... Please post again.
Thanks,
Pete


Sorry, here it is. Just enter page 2517 in the search field. http://www.mcmaster.com/

Envy Lawn Service
06-29-2003, 01:36 AM
DLCS,

That's different from what I used. Mine has a flexable (to a point) plastic disc holder and you just put whatever grit sanding disc you want on it. Like sandpaper.

This will probably work great on wave style mulching blades.

I will have to order some of those like you have from McMaster.

DLCS
06-29-2003, 01:37 AM
Envy,

I'm glad it worked for ya. I started using those sanding discs last year. I like them better than grinding wheels since the blade doesn't get so hot and also is quicker.

DLCS
06-29-2003, 01:41 AM
Originally posted by Envy Lawn Service
DLCS,

That's different from what I used. Mine has a flexable (to a point) plastic disc holder and you just put whatever grit sanding disc you want on it. Like sandpaper.

This will probably work great on wave style mulching blades.

I will have to order some of those like you have from McMaster.


Ok I know whick ones you are talking about. Get ones like I linked too. They will last last so much longer. I sharpen mulching blades with them too.

Envy Lawn Service
06-29-2003, 01:44 AM
Originally posted by DLCS
Ok I know whick ones you are talking about. Get ones like I linked too. They will last last so much longer. I sharpen mulching blades with them too.

Consider them ordered!!!!;) :cool: :D

HayBay
04-09-2004, 01:41 PM
So I was looking everywhere for a way to grind my blades.
Magnamatic to Canada seems to be dificult plus I read there is a 4 week delay on all orders now. Tried their Alberta supplier and they didnt return my call. So I checked out Oregon. They have one which looks nice but will take some time to get here too.

Then I went to the local golf course to get the blades sharpened, the guy there says they send all theirs out.

What to do I say.....

I get on Lawnsite, do a search for 100 grit because you need 3 letters to do a search. I really wanted to search for 60 grit.

Anyhow, came across this post and saw the suggestions about grinding discs with 24-36 grit sand paper.

I knew I had a 36 grit set up on my belt sander, so I went and made a simple holder for the Belt sander to sit up at a Level vertical position on my work table, cut a 40 degree angle with 2x6 P.T. wood and attached it to my work table in front of the sander. Slide the blade along that 4-5 times and bam.... Instant sharp. No heat buildup at all.

What a great and very low cost Idea, Thanks guys..

CEGreen
03-05-2014, 11:32 AM
Ok, so the last comment on this post was from 10 years ago. Is the flap sanding disc still the best to use for sharpening mower blades? What grit should be used? Didn't really see a consensus in the thread.

TTS
03-05-2014, 12:03 PM
They all work. Flap discs belt sander magnamatic or a file. Depends what you got and what you need. I personally use a belt sander because I am a knife collector also a hobby woodworker and I use it to sharpen all of my other tools. For a quick job when I'm not taking the blades off I will hit them with an angle grinder
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gardiner
03-05-2014, 06:25 PM
Go get a bench grinder from lowes and while your there grab a wire wheel that will fits the grinder you are buying .and a few spacers ,

take the course one off and replaced it with the wire wheel .
using them spacer to get wire wheel nice and tight .

you can clean and shapen a blade in 2 min like the shops .

i pounded a nail on side of bench . to use as a level ,
and a place to keep the safty glasses when not in use .

After a few times you have it ,, and friends and family will come to you for a sharpening

Magna-Matic
03-07-2014, 02:19 PM
Hello All,

Feel free to take a look at our educational information and our equipment at www.magna-matic.com

We are the oldest manufacturer of lawn mower blade service tools, and the only sharpeners that will maintain consistent cutting edge angles. We invented the industry standard lawn mower blade balancers that professionals and blade manufactures have used since 1958.

Here is an educational video explaining why a NAIL should NEVER be used as a method to balance a lawn mower blade.

http://youtu.be/x3RMN1QfutM

Thank you,

Choppin
03-08-2014, 09:52 PM
I have never balanced a blade and my mower runs smooth and cuts smooth. Why is it such a big deal to balance.
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worm1
03-09-2014, 06:22 PM
I have been using 60 grit flap sanders for over 10 years, they are fast, easy and cheap. We use them on blades, spades and axes.
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Bryan27
03-10-2014, 06:10 AM
I have never balanced a blade and my mower runs smooth and cuts smooth. Why is it such a big deal to balance.
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If your blades are out of balance they can cause damage and wear spindles out faster than balanced blades. I think it's to be expected that they are going to be out of balance to some degree, it's a matter of how precisely you want to measure. Same principle as balancing a tire on your truck, if you've ever lost a wheel weight and then went down the road at 60mph you know how something as little as a 1 ounce weight can make a 70 lb wheel and tire become unstable.

For a comparison:

20" lawn mower blade at 18500 fpm tip speed is moving at 210 mph. The circumference of the blades' path is 62.8". So 18500ft x 12in / 62.8in =3535rpm's.

35" tire going down the road at 60mph: 63360inches in a mile, 110 inches per revolution... 63,360/110=576rpm

Your lawn mower blades are spinning about 6 times faster than your tires are when driving 60mph.

I'm sure that wide tolerances are engineered into the spindles on a lawn mower because as soon as you start cutting with a perfectly balanced blade it's going to be out of balance again, but it's probably good practice to stay at least pretty close to balanced. Not to mention what happens when you hit something besides grass with the blade moving at those speeds!

rockymtnnut
03-12-2014, 12:11 PM
I've been told the flap sander works great I've used course grit grinders with good success but two years ago I started using a very large file this I get the best edge.
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