View Full Version : Sharpening Blades

Expert Lawns
08-08-2002, 11:55 AM
all i have is a bench grinder. i don't think i'm sharpenin them the right way. they dull fast and are inconsistant. how do you guys sharpen your blades and whats the best way to use the bench grinder. maybe i'm taking too much off or going at a bad angle

08-08-2002, 12:03 PM
I remove them and use a hand file. I keep 4 sets (2 gators + 2 highlift). I'll pull 'em off and jam on the other set. Sharpen the dull ones I pulled off when I fell like it.

Cut 2 Please
08-08-2002, 12:16 PM
You really need a dedicated blade sharpener. I use a friends RBG now but I am saving to buy a Magna Matic. You will find that many people here love the Magna Matic. There are several problems with using a bench grinder. 1) Many times you do not get the proper angle on the blade. 2) I always seemed to get hot spots on the cutting surface which weakens the blade and lets it dull faster. 3) Unless you are really good your cutting surface will have a wave pattern. 4) The blade will tend to be unbalanced.
I use to sharpen blades on a bench grinder and had the same problem as you. I then started using a disk grinder with the blade being held in a vise. This worked better. However when I discoverd the RBG blade sharpener I realized how blades are supose to be sharpened. If the Magna Matic is so much better than the RBG like I have read in many posts I have to have one. Do a search and you will find a wealth of info. Also Magn Matic is an advertiser on this site and there is a link to their web-site.

Doc Pete
08-08-2002, 12:59 PM
I don't seem to have a problem using my grinder. You'll get better results with at least an 8" diameter 1" wide wheel. I adjust the grinder base plate, where I rest the back of the blade on, so that the back of the blade is in the middle, when the face of the blade is at the correct angle for sharpening. I sharpen my blade at about a 30 degree angle, which more, or longer than at 45 degrees. You also need the "extremely" rough grit number, which is lower than the "rough grit" of #46.
All I do is hold the end of the blade with one hand and position the other hand as close to the end I intend to sharpen, without bumping into the grinder, as you slide the blade back and forth. Besides needing a welding glove for the hand close to the end your are sharpening, I use "aluminum tape" wrapped around my thumb, otherwise the amount of red hot metal coming off the blade with burn a hole through the thumb part of the glove. It takes me about 5 minutes to sharpen and balance one blade, 15 minutes for 3.

08-08-2002, 01:48 PM
this will work tho theres better ways that cost more money.
1 take time on the edge and never allow the metal to heat up. this happens and the steel edge breaks like glass.
2 use more angle than is normal .
this will allow more support to the edge and will hold edge better for me.
3 just knock off any burrs on the bottum of the edge. dont sharpen from that side.
again take plenty of time so it does not build heat.
like i said theres better ,more modern ways . but this works pretty good for me .
i forgot, did i mention dont allow any heat to build up . any blue or black edge aint gonna stay past the first yd.
good luck to u.

Expert Lawns
08-08-2002, 01:59 PM
thanks for the tips guys. wow, that mega matic sharpener costs a pretty penny.

now, why does heat play such a big role?

Cut 2 Please
08-08-2002, 02:08 PM
The heat weakens the metal and makes it more brittle.

Expert Lawns
08-08-2002, 02:22 PM
so when the blade gets weak, it doesn't stay sharp as long?

08-08-2002, 04:04 PM
Originally posted by Expert Lawns
wow, that mega matic sharpener costs a pretty penny.

Expert, I know when I first found LS and saw guys talking about these $500-$900 blade grinders, I was like "no way I'm spending that kind of money for a simple blade sharpener!, That's crazy!".

Now I can't wait to get one! I was taking 8-10 blades a week to a sharpening guy and paying $5 per blade. THis was running me $40-50 a week. I'm only cutting part time right now, so once a week is all I need, but when I go more full time next season these blades would have to be sharpened every one to two days!! That's gonna add up REAL quick. Hell, it already is. I could have already paid for a nice blade grinder by now.

Not to mention the time it was taking me to drive to the sharpener and wait while he sharpened them and drive home.

I did buy a bench grinder to hold me over until I can get a dedicated grinder for next season. Not as happy with the edge, but it's saving me alot of time and money for now.

How many blades are you sharpening and how often? Do the math and you'll see why you probably NEED a dedicated grinder too.

08-08-2002, 04:05 PM
I got a dedicated blade sharpener that normally cost about $375.00 off of ebay a couple of years ago and paid $125.00 plus $20.00 shipping. The thing was like new and works great!;)

08-08-2002, 04:51 PM

I thought i'd drop a note here about the burning or blueing of steel and its effects.

Most Lawn Mower blades are AUSTEMPERED. This is a type of heat treating that increases the ductility of the steel. Lawn mower blades are not HARDENED, if they were when you would hit a rock or curb they would crack/shatter/break. In a very short explaination the metal is brought up to a certian temperature and then is quenched in molten salt. There is a difference between tempering and hardening of steel.

Also note this is done after the blade is manufactured, i.e. the blade's edges have already been milled on.

Now if during the sharpening of a mower blade you turn an area of the steel blue this is thought to remove the temper from that area. In general you want to NOT blue the blade when sharpening, however if the blade discolors to brown you have not raised the temperature of the steel high enough to do any damage.

Also a note about mower blades, never try to straighten a mower blade. Doing this can create micro-fractures in the steel, making weak points that may shatter after hitting a rock.

Lastly a product plug: All of MAGNA-MATIC sharpeners can sharpen a blade in under 60 seconds without blueing the blade.

Thank you, i hope this was of some help.

08-08-2002, 05:17 PM
I would agree that a true blade grinder would probably be best, but I too have a hard time justifying the cost of one. That said, I do very well with my Delta 1/2 hp bench grinder that I bought for about $75 ... it has a fully adjustable fence which I have set to about a 32 degree angle. I can do a blade in about 4-5 minutes, debbured, sharpened, and balanced ... if it hasn't met up with any rocks, about 7-8 minutes if it is bad. I may be a rarity, but on occasion a few guys at lawn mower shop have seen the angle and smoothness and have made comment that you could even shave with one of my blades.
BTW, you should really be changing blades daily, that way they never get too bad and are easier and take less time to sharpen and your customers lawns won't complain that you are beating them to death ...

Expert Lawns
08-08-2002, 05:20 PM
talk about detailed sharpening........i'll have to look into a good sharpener soon. thanks for the tip

08-08-2002, 06:38 PM
I find that a handheld angle grinder works great for me. 2-3 minutes per blade.

08-08-2002, 06:51 PM
I too went the grinder route, and then discovered a hand held 4.5" grinder and a vise to be much more effective. If blades are sharpened on a daily basis it won't take more than a minute or two per blade. If they are really gouged due to hitting a rock, etc., it still would never take more than 5-6 minutes per blade max. I'd love a professional grinder, but can't seem to justify the cost. This is a part time business for me until I retire from my "real" job.....maybe then!!

Doc Pete
08-08-2002, 08:37 PM
Originally posted by Cut 2 Please
The heat weakens the metal and makes it more brittle.

What changed everything for me was going from the 46 grit, which is said to be for rough grinding and the coarsed wheel that many catalogs offer, to the one labeled for deburring only. It's something like 23 grit.
The 46 grit heats up the blade very fast, and really doesn't take off material fast. It is very hard not to blue the blade with the 46 grit.


08-08-2002, 08:59 PM
get a magna matic we just got one a while back and it is much better then the rbg that it is replaceing.

They are fast and easy to get the right angle everytime.

08-09-2002, 12:32 AM
I'm with you Tom and Westbrook. Hand grinder is the way to go. Just try it for a week till you get a handle on it. I think it makes my blades last twice as long since I can put a sharp edge on the areas that have hit objects without grinding the rest of the blade down to "meet' the damaged area. I can also put on a quick edge at a slightly elevated angle when I'm in a hurry. The only thing I use my blade grinder for is to hold my blades on while I'm sharpening them with my hand grinder.

08-11-2002, 06:59 PM
This post is for PETE (CUT 2 PLEASE)

In grit sizes the lower the number the more coarse/porous.

The grit size has far less to do with the burning or glazing of grinding wheels than the HARDNESS does. All of the bench grinders that you are used to have very hard grinding wheels on them. This is one of the reasons why they sharpen so slowly and burn blades.

A 46 grit is what MAGNA-MATIC sharpeners use, and there are no burning issues.

The problem is that in a bench grinder arbor hole size (traditionally 5/8") the wheel hardnesses are limited to very hard wheels. A bench grinder is made for sharpening HARD steels such as tool bits or chisels. A lawnmower blade is relatively soft ductile steel.

Thank you,

08-11-2002, 07:17 PM
I have a Neary blade grinder that works ok for now. I will be getting a Magna Matic as soon as I can swing the cost. Too many other things this year have eat away the money (if you know how that goes). However I will say that if you guys arent balancing those blades your missing the boat.

I did get my new Magna Matic blade balancer (Thank you) and wow what a difference from the old worn out one I had. This thing is so smooth and has made a huge difference in how my mowers cut and feel when running. If you dont have a balancer I would strongly encourage you to get one soon. It will make that much difference, plus you wont ruin any spindles or anything else due to out of balance blades. Try it, you'll like it!

08-11-2002, 07:19 PM
I too have the MM itch.

There is no comparasent to a bench grinder or a hand held grinder.

I have used a Lesco for the past ten years or so, and a buddy bought an MM and I barrowed it for a week to see if there was a difference. Yes there is.

My only problem is I have a blade sharpener so it is hard to justify the cost of the MM right now, but they are a time saver over the other brands.

As far as dedicated grinders go, the best thing for the blades is the uniform edge you get with one.

I have seen radial arm saws converted, to the Magna-Matic and there is no comparesent. The MM was designed to sharpen lawn mower blades.

08-11-2002, 10:43 PM
The usefulness of the Magna Matic is about 80% due to the grinding wheel they use. It is a Norton 32A46-IVBE, and it is rather soft. It will cut the steel off of a mower blade very rapidly, bringing a very well worn blade to sharp condition in a matter of about a minute or less. Because the wheel is so soft, and because it cuts so fast, the blade doesnít get as hot as with other wheels. Of course the trade-off for the faster grinding is that this wheel wears out quickly. I think the speed it provides is well worth the cost and length of life.

My brother uses this same wheel on his Craftsman (sp.) bench grinder that he modified to sharpen mower blades. He found an adapter at ACE hardware to bring the 1-ľĒ center hole down to 5/8Ē. Norton will tell you that doing that can be a problem, but he hasnít ever had any.

I use a DeWalt bench grinder along with a special rig that allows me to clamp the blade and cut at the correct angle. I use the Norton 32A46-KVBE wheel. This wheel is a little harder than the IVBE, so I canít zip quite as fast, because if Iím not careful it will cause the steel to overheat. But when that happens I just quench the blade tip in water.

Using a wheel like the Norton 32A46-IVBE for the first time is like going from a 21Ē Murray to a Dixie Chopper.<G>

08-12-2002, 09:44 PM
You are correct. The grinding wheel is a large part of what will increase the speed, but i would not equate it to 80%. There are a number of other aspects of MAGNA-MATIC sharpeners that allow for a very fast and well sharpened blade.

Rigidity of the machine, material support where the cutting is being done, motor speed balanced with the grit/hardness/composition of the grinding wheel used.

I will also mention the use of "adapters" is frowned upon by NORTON. Their product liablity will be voided if you use them. Now that is not to say that they do not work or are not manufactured, because THEY ARE used and manufactured. Just be aware if you use such things you will not be able to blame the MFG if you get hurt or if the product does not perform.

Of course the best is to use the correct grinding wheel for the arbor on the grinder.

I understand price is a big factor in the decision of a dedicated mower blade sharpener, and i also understand that not everyone is taking their blades to get sharpened. But i have spoken to many people that spend the amount of a MAG-9000 and some of a MAG-8000 or more on sharpening costs in one season.

As you must with any purchase, be sure to weigh all benefits that are associated with a cost before you make a decision. Also remember all of our equipment is capital equipment (much like your mowers) in the accounting function the cost is depreciated over a number of years.

Thank you,

08-13-2002, 02:01 AM
I use a bench grinder (and have for almost one year) but am getting real tired of how I end up with (1) waves and (2) the wrong angle.

I've tried to hold off but am have made a decision to get a magna matic 9000 next week. Will let you all know how it works out but I'm expecting that with my exta time I should be sitting on the beach with an umbrella in my cocktail !!!

Hey rep, do you know is there a place that sells your 9000 in Scottsdale, AZ or should I just buy it online from you guys?


08-13-2002, 11:22 AM
Originally posted by spomerhome

Hey rep, do you know is there a place that sells your 9000 in Scottsdale, AZ or should I just buy it online from you guys?


Rep would be the VP. Buy online.

08-13-2002, 11:44 AM
Well, we do have some lawnmower dealers that handle our products but we mainly sell the grinders direct from us (the factory). This allows us to really control quality and customer support.

You can call or fax in your order, or use the best deal ONLINE where you get free shipping.

Thank you,

08-13-2002, 08:11 PM
Thanks Godfather.

Gerd, I didn't mean to insult you but by the time I started typing my reply I couldn't remember your name to type it in my reply.

Appreciate the info, will post to you all with is what I am quite sure high marks on the MM when I start using it.

08-14-2002, 12:50 AM
Don't worry about it.... i was not insulted at all ...

I am just trying to do my best to provide additional information to help people make the best purchase decision for their need, and to learn the best way to service their lawnmower blades.

Thanks for the questions .. keep them coming! :D

08-14-2002, 05:45 AM
Our blade bench has a standerd grinder w/ I think a 80 grit wheel and a brass wire wheel for cleaning....1 st clean with the wire wheel...then take out bad spots on the 80 grit . Then move over to the RGB grinder for the finish edge.....on to the Magna Matic balancer.....and if the blades will be out of service for awhile a lite coat of cheap spray paint so they do not rust.You should see the finished product with this system....its the only way to go IMO.