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Threw together a video series on how to properly sharpen mower blades for anyone interested.

My blade sharpening video here (Part 1 of 2): https://www.youtube.com/watch?v=c0tuWqYE7BU
My blade sharpening video here (Part 2 of 2): https://www.youtube.com/watch?v=HgHsY_2Yqe0


Cheers!

With all respect, I must offer some corrections. I use a bench grinder but the principle is the same. The direction of the grind should be towards the sail of the blade and not the direction shown in this video. Also the bottom side should never be touched. The sparks should always fly towards the sail or lift of the blade. This will avoid any burrs on the bottom, so no need to clean up. Balancing is very important to preserve bearings in the engine. Other than that, everything is right on and a very good video.

Its amazing how everybody is different.

I would never use a bench grinder as don't have the same control as an angle grinder.
I always grind on the bottom so that my customers can tell that something has been done on the machine when they tip it over (as nine out of 10 customers do check).
Also you want to grind at the same angle as the blade wing as it makes flow easier for collecting.
Also the new way for mulch is instead of a blade that has a low point then an angle and then a high point, they are flat and the cutting edge is ground all the way along to just about the middle of the blade.

I use a bench grinder and try my best to keep the factory pitch. And the wing is up with sparks going away from the wing. But will try with blade flipped over so don't have to hit the bottom side to clean up

Sent from my iPhone using LMF

I sense that I might have been misunderstood. We all have our own ways to achieve the same goals. I just happened to have my camera here at the shop today, so I will do a pictorial. Also, I will look into my files and see if I can find my Toro service school hard copy on "sharpening" I have an employee here that sharpens blades a minimum of 4 hours a day 5 days a week. Thats all he does. I go through one 8 inch ruby grind stone a month. It took almost 2 weeks to train him to sharpen correctly for a "long lasting" sharp hollow ground cut.
I'll post pics later

OK the first pic is a dull blade with (self inflicted) nicks.

The second pic is removing the nicks to have a uniform foundation in which to grind a 45 degree angle. Notice the grind is "square" to the bottom of the blade.

The 3rd and 4th pic is a view of this square grind

Edit:
Hmm, the pics show a different order on the post than when I uploaded, but you'll figure it out.

continued

This 1rst pic is grinding the 45 degree pitch to the blade. Grind with pressure until you see the sparks start to go over the blade, then lighten up

The 2nd pic is the finished blade. As I look at this pic on the computer, it is deceiving because the blade wasn't laying flat when the image was captured, but it "is" 45 degrees.

The 3rd pic is something I cant do without. It not only balances the blade but checks for it being straight too. There are inexpensive ones on the market too. A blade that is even slightly out of balance causes even slight vibrations. This puts stress on engine brgs and or spindle brgs

These pics are from a service school I went to in around 1980, but the principals are true for today. Notice one of the underlined "don'ts"

Something I might add, is that a quality cut, (something that is required by my clients) does much more than just look good. When you have "poorly" cut turf with split ends, it actually promotes disease and yellowing.

Whoever that was that sent me an E-mail message,, forgive me but I deleted it and forgot (oldtimers disease) to reply, but thank you for your kind words.

I use a Work Sharp flat grinder to grind my mower blades. It's slower rotation speed doesn't get the blades hot (grinding with a high speed grinder will form the edge, but you will find that the heat removes much of the temper, and the blade will dull faster after the sharping).

Work Sharp WS2000 Tool Sharpener - Amazon.com

I start by cleaning the blade with a wire brush, then dressing (light grind) the back side of the blade for a flat reference point. (The edge of the blade is referenced from the flat, back side).

I then remove the nick's from each edge so I have a fairly flat edge to reference from and try to remove the same amount from both sides so that the width of the blade is the same on both sides.

I grind at an approximate 30 deg. angle (whatever was on the blade to start with) I leave a flat edge on the blade of 1/16" (per blade spec.) Any sharper and it gets too thin and the edge will nick or chip faster.

After sharping, I use a wall-mounted balancer (the kind with ball bearings and magnets) to check and correct the balance. (Ebay, used).

Balancing is important as any imbalance will shorten the life of the lower spindle bearings or lower engine bearings. (And it makes for a smoother running mower or mower deck as well).

If I need to remove material to get a blade to balance, I extend the sharpened edge length-wise by 1/16" increments from one or the other side, until the blade is back in balance. (I try to maintain the same front-to-back width of the blade on both sides for dynamic balance. Extending the sharpened edge length-wise doesn't change the dynamic balance.)

The problem of using a nail is, they don't work with blades with a star-center hole, some blades have no center hole and even with a standard center hole, the nail never really gets positioned at the center of gravity of the blade properly.

I recommend that you do balance after every sharping and to use a small, cheap cone-type balancer. Should only cost $5 and more accurate than a simple nail as it will center the blades center hole better.

Please...bench grinders will not over heat if used properly. Clean wheel. Any wheel diameter . Grits of 46-80. Reasonably fast grinding passes of 5-7 seconds on an 18 " blade. Such grinding does not even warm the blade too hot to touch. Any grinding leaves sawtooth edges which are beneficial. (The barber's scissors are purposely ground with teeth). Stay off the back side of the blades except to remove the burr. Mower blades do not cut steak or scrape fine furniture wood. :2cents:

chance123 said:

OK the first pic is a dull blade with (self inflicted) nicks.

The second pic is removing the nicks to have a uniform foundation in which to grind a 45 degree angle. Notice the grind is "square" to the bottom of the blade.

The 3rd and 4th pic is a view of this square grind

Edit:
Hmm, the pics show a different order on the post than when I uploaded, but you'll figure it out.

continued

Click to expand...

Picture two is nice , but would be better if the "secondary" clearance were there. This is has also been called "slope" or "bevel".

Eganwp said:

Threw together a video series on how to properly sharpen mower blades for anyone interested.

My blade sharpening video here (Part 1 of 2): https://www.youtube.com/watch?v=c0tuWqYE7BU
My blade sharpening video here (Part 2 of 2): https://www.youtube.com/watch?v=HgHsY_2Yqe0

Cheers!

Click to expand...

Heck ya you used a flapper wheel that's honestly how I sharpen my blades never use a grinding wheel only flapper it does a great job in my opinion

Those of you that use a bench grinder, A "Ruby" stone is the coolest, and longest lasting stone.

motoman said:

Please...bench grinders will not over heat if used properly. Clean wheel. Any wheel diameter . Grits of 46-80. Reasonably fast grinding passes of 5-7 seconds on an 18 " blade. Such grinding does not even warm the blade too hot to touch. Any grinding leaves sawtooth edges which are beneficial. (The barber's scissors are purposely ground with teeth). Stay off the back side of the blades except to remove the burr. Mower blades do not cut steak or scrape fine furniture wood. :2cents:

Click to expand...

Grinders can get the blade too hot (a good example of this is some of the videos we see on You-Tube. In many cases it's evident those blades are being overheated.)

In most cases, I feel a lawn mower blade is best sharpened using a bastard file. (I switched to using a Work-Sharp for several reasons, not just lawn mower blades, but it is faster than filing, and the slower speed doesn't heat the blade appreciably).

I would however recommend using grinder if you see nicks in the blade. (A grinder will remove nicks in the blade much faster than you can file them.) Even so it becomes important not to overheat the blade. Another negative side-effect is that it's more difficult to follow the same angle of the original blade hand-holding a blade against a grinding wheel. The effect you see is a waviness after using a grinding wheel. You will not see this using a file (or Work Sharp).

Most home grinding wheels are usually in the 5"-6" range. Grinding with a small diameter like this has a tendency of producing a hollow ground effect on the blade. (Again, you will not have this problem using a file of flat grinder like a Work Sharp). Hollow grinding is good for a knife edge, bad for mowing grass (too little material at the edge). In such cases, I feel it better to leave more of an edge on the blade, perhaps as much as 1/8", to keep the thickness of the blade edge sufficient for hitting roots, rocks, etc.)

While I would also not recommend grinding hard on the backside, I feel a light grinding is beneficial to establish a true, flat edge. (This would not be possible using a bench grinder, but easy with a bastard file or Work Shape.) This is the point at which the edge of the blade is referenced from.

Lastly, I agree that lawn mower blades are not being sharpened to reflect the edge of a steak knife. New blades have an edge similar to that of a butter knife; which is exactly what we are trying to achieve.

Thanks for sharing you opinions,
Dennis

enigma-2 said:

Most home grinding wheels are usually in the 5"-6" range. Grinding with a small diameter like this has a tendency of producing a hollow ground effect on the blade., bad for mowing grass (too little material at the edge).
Dennis

Click to expand...

I sharpen (well, my employee does) 200+ blades a week and for me, a file is out of the question. After 40+ years in this business I have gone through several training seminars on sharpening and by experimenting and by Toro's recomendation, I have proved (to myself) that a hollow ground blade "lasts" FAR longer before it needs resharpening. I "strongly" suggest trying for yourself just like I did to see the truth in this method. I think you will be surprised just as I was. The difference is very noticable.

It is of course true any method of sharpening blades may be overdone to the detriment of the blade. I find I cannot remain silent on a couple issues. Anyone can put a grindstone to a blade and hold in one place until the geometric form is achieved. That form may be some desired angle or a hollow formed by the grindstone radius. If that is done without heat control the result is a burned, softened edge which will not hold up.

A hollow grind is a thing of beauty and I would prefer it , however...( I have never used a jig or guide for this) I bet besides an expensive grindstone ($25, $45, $ 55?) some sort of air , oil or water cooling is used as the stone "digs" out the hollow and then in a secondary pass the edge is put on.
Right? Beyond the scope of most home sharpeners. Incidentally, although a statement may have been made that manufacturers don't use this method my new Craftsman blade had a hollow grind which I was sorry to see go. I also see Wal Mart's array of blades where about half seem to have hollow grinds.

Next is the example with picture above of a jig ground blade where the edge is quite wide with no apparent burn. For that good result no doubt an expensive "friable" stone was used where the grains constantly break off to avoid over heat. Right ? Stones like Norton etc...? $35, $45 ? And a $300 jig?

You cannot use a Harbor Freight 60 grit grey wheel and do hollow or wide single angle edges without burning. What causes the softening is the dwell time on the blade to achieve the form. On a thick (150-.200") blade holding the angle while removing all the metal burns the cutting edge.

The technique to use while dry ginding with a cheap wheel is to grind the thick part first behind the cutting edge, and then the cutting edge. You can exert sufficient pressure on the grinder to remove the thick material (called secondary bevel by the pros), and then be much gentler when putting on the cutting edge which is a much narrower band. This technique narrows the blade. No burning should take place.

I believe all these different techniques and beliefs should be resolved once and for all. If you all can not agree with me then we need to hold a national "Grind Off" somewhere in Kansas or mid USA. The winner will get a years supply of his favorite abrasive....and I don't mean someone who has a different view. Happy grinding and keep your fingers safe.

I also think this topic is going a little too far.
In my field, working with professionals who mow 10 hours a day 6 days a week (probably 8 actual mowing hours per day) comes out to 48 mowing hours a week according to the hour meters. A commercial mower will run in "one day", what a home owner (mowing 2 hours a week) will put on in "one month"! They put on in one week, what a home owner puts on in six months! So for me, these things are very important to keep my clients machines in top shape the best I can. For a home owner, these things are less critical because of far less use. Here in Southern California, they mow 12 months out of the year, and they have many machines that are more than 5 years old and still running strong. With the ratio of hours between a home owner and a commercial, you can see that a 5+year old commercial has probably more continuous operating hours than most home owner machines that haven't already rusted out or a failure of some kind and not worth repairing. I am only sharing things I have learned and continue to learn. We all have different ways to our craft to reach the same goal. Happy grinding, flapping, and fileing.

motoman said:

A hollow grind is a thing of beauty and I would prefer it , however ..

Click to expand...

That's interesting and I appreciate the time you take to put into your remarks, but the ideas I was referring concerning the bench grinder, is best illustrated in a You Tube video.
Work Sharp 2000 Sharpener and Precision Grinder: Demo The part about hollow grinding with a bench grinder starts around 3:50. It's a little exaggerated when it come to the thickness of a lawn mower blade, but the principal is simular.
Anyway, thanks for your remarks.