Blade Sharpening - a PRO's Perspective: Part 1

Hello Everyone!

A friend knowing I own & operate a professional lawn mower blade sharpening business referred me to this site and after reading a number of posts I knew I had to lend my 50 plus years experience and try to answer questions as well as provide members with "real" information.

I am still in business and have tried just about every form of blade sharpening techniques through the years - both because they were state of the art at the time as well as I wanted to give them a go out of shear curiosity.

Let me start with the ABSOLUTE basics before we go into the details.

First, a blade MUST BE BOTH SHARPENED AND BALANCED. To do one without the other is akin to trying to balance bogus tires or buying new tires without balancing. Later we will get into the techniques of both. But for now, RULE #1 is you MUST both sharpen and balance your blades.

Blades MUST be spotlessly cleaned prior to sharpening AND BALANCING. You would not let your tires be balanced with mud clinging to them, right? So this is RULE #2.

Understanding these two rules takes us to RULE #3: to perform rule # 1 & # 2, your blades MUST BE OFF OF YOUR MOWER. Therefore this is RULE #4.

OK - back to the tire analogy ... and those who feel balancing a blade on a nail is OK. You CANNOT accurately balance a rotating object from anything but it's precise center ... your tires are balanced from their center of rotation and that is how your blades MUST be balanced.

Hanging a blade on a nail or a screwdriver held in a vise is a joke. Rule #5 - balancing on a nail is a wive's tail.

Some will argue "it works" but you need to experience the difference in using a precision balancer. Why? Simple. Offset rotation, meaning an imbalance, translates into vibrational energry. Think about a tire causing a vibration. Will it wear out far more expensive steering components than the cost of the weights and the balancing? Yes it will. So will blades out of balance. The cost appears as replacement crankshaft bearings, spindle assemblies, labor, etc.

There are so many You-Tube videos showing how to sharpen how to balance, etc. which have been put together and placed "on-air" for you to view that it is ever so hard to discern the truth from the BS.

Here's some info from our OWN WEB SITE ... HOWEVER, ONE RULE HERE IS NO ADVERTISING and I will abide by this. But this does not mean I cannot copy the facts here for you provided I do not advertise (disclose) our web site and violate the trust this forum requires.
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MYTHS, SNAKE OIL, and "EXPERTS"
On this page we would like to help you learn about the "smoke and mirrors' regarding blade sharpening, and the like.

The internet provides a wealth of information - mostly good, but some bad. Unfortunately there are several You-Tube videos by "Experts" instructing viewers how to sharpen and balance their lawn mower blades, and most don't even mention how important balancing is. And we have yet to view an "Expert" showing you how extremely important it is to check your blades for straightness and clean them.
You are NO "expert" unless you include ALL of the process steps shown HERE.

This is the difference between a non-professional (sometimes a "hack" masquerading as a PRO) and a true Professional who actually performs ALL of the mandatory steps shown HERE to properly, safely, and completely process a lawn mower blade.

After you read the following, you too should be able to spot the bogus information rampant on the internet.

Debunk the Junk!

The Science, Mechanics, and Logic Involved

Re: Blade Sharpening - a PRO's Perspective: Part 2

(cont'd)
Rotational Energy -
Think of a vehicle tire. To get it balanced would you bring it in coated with mud? And if you did, wouldn't you think a responsible shop would make sure the tire was very clean before putting it on the balancer? You don't? Why not?

Understand this - you cannot possibly achieve a lasting and accurate balance with junk clinging to the tire ... and neither can you with a lawn mower blade. It MUST be clean.

But a lawn mower blade spins slowly, so why should I worry? For several reasons. First, a blade does NOT spin as slowly as you might think. A blade can rotate around 2800 RPM to 3500 RPM, typically. So for a 21 inch blade rotating around 3000 RPM, the tip is travelling about 187 MPH, and at 3500 RPM it's about 218 MPH. In a car, you are inside, protected from a non-speed rated tire should it come apart. But walking behind a mower, you (and others nearby) are exposed - and could be in the way of metal fragments an overly worn, cracked, or fractured blade flings off.

Inspection -
Ever strike a rock? stone? Other hard debris? Do you remove the blade and inspect it for apparent damage? for cracks or fissures? And if the blade is not clean, might you overlook hidden damage?

Why You MUST Remove the Blade and Clean it Thoroughly to Service it -
First, the blade HAS to come off the mower. PERIOD! It has to be removed for sharpening. Why? Simple - it has to be properly cleaned, inspected, and balanced after sharpening.

And why do some not remove it? Laziness may be a reason. Not knowing how to may be another. A lack of tools could be another. We may be able to motivate you to overcome the lazy aspect. But we can definitely help with learning how to take a blade off as well as loaning you the tools to do this. Alternatively, bring us your equipment and we will take the blade off, clean, sharpen, balance it, and put it back on for you - overnight! We have yet to see a You-Tube video where the "experts" show you the importance of a thorough blade cleaning .

How NOT to Sharpen a Blade -
So, the drill attachment I can buy for five bucks is a bad idea? Absolutely - it's Snake Oil! It's a terribly bad idea as you won't be able to thoroughly clean a mounted blade, you cannot see both surfaces to inspect for cracks and fissures, and it is impossible to balance the blade while it is attached to the mower. Because of these reasons, the You-Tube videos showing this sharpening method are ridiculous. Plus the angle you will attempt to grind will vary as will the "edge" you create. We rank this as a junk "Snake Oil" tool.

OK, another You-Tube video shows a guy with a blade mounted in a vice and he says to use a file - what do you think? We think you have better things to do than try to hand sharpen a blade with a file. Seriously - you won't achieve a consistent cutting edge, you can't hold the proper angle (even if you think you know what it is) and if the blade is as worn as most we see from people remiss in keeping their blades sharp, you'll spend the better part of your day with this method. And after you get it "sharp", how will you balance it? And you did thoroughly clean and inspect this blade before you spent time sharpening it, right?

Then there are numerous You-Tube videos showing a Bench Grinder. Again - lack of a proper tool to form a consistent edge, inability to properly sharpen "wavy" style, curved blades, and not enough power to grind in a reasonable amount of time without overheating the blade which causes the steel to turn blue (or even black) indicating you have just removed the temper (hardness) from the metal.

Hand Grinders. You know, those right angle electric motor grinders often found in automotive body and welding shops. And that's a good place for them. There is no way this hand held tool can consistently grind an edge, nor form the proper angle all the way along the cutting edge. This is why we call this tool laughable as it is like trying to carve a turkey with a piece of wood. It's simply the wrong tool for the job, and for all of the same reasons previously mentioned.

How NOT to Balance a Blade -
A lot of You-Tube videos tell you to hang your blade on a nail hammered into a wall. Bad advice. Think for a moment ... the blade is bolted on to your mower using the center of the bolt hole and then rotates about this center point, doesn't it? So does it make sense to use the edge of the bolt hole rather than the center? Of course not! To be accurately balanced, the blade MUST (a) use the bolt hole and (b) be perfectly centered in this bolt hole. Now think about just how good a tool is a nail. It has no bearings, so it has no precision nor the smoothness only a precision machined tool with precisely machined bearings can provide. Due to numerous reasons, a nail is a joke. Would you let your tires be balanced mounted off center on the balancing machine? If you are using a nail, don't be offended - just try something better than a nail and you too will laugh at using a nail.

Why not use a "stepped cone" balancer, after all You-Tube videos say use these so they must be OK, right? Wrong. A stepped cone has several pre-determined step diameters which almost never precisely fit the exact diameter of your blade bolt hole. So like a nail, the blade most likely is off center. And like the nail, this balancer has no bearings, lacks precision machining, and seems to wobble forever. Add to this what you have set the cone atop - is the bench or table perfectly flat so you can get precise readings at the end of the blade? I doubt it, so you probably settle for "good enough". But it isn't - it isn't if you care to keep from ruining crankshafts or deck spindles.

Blade Straightness -
None of the above balancers can check the straightness of your blade. The cone can't and the nail sure cannot. So how in the heck do you do this? Lay it flat on a table? Wrong. There is NO way this will work as the blade lying on a flat table top plane has an absolute ZERO reference to its blade bolt mounting hole in the middle of the blade! There is but one way - and this is to allow the blade to pivot from the center of the blade bolt's mounting hole and then measure to determine if the blade tips are equidistant from a fixed reference point. And this absolutely MUST be done, particularly if the blade has struck a good size rock, stump, curb, or some similar strong (perhaps) immovable object. Without the right tool to do this, you have absolutely no idea whatsoever if your blade is still within its flatness tolerance.

Blade Sharpness -
Unfortunately, many individuals do not understand the importance of maintaining a sharp lawn mower blade and that's a shame for it is only the blade which is cutting your grass. Fortunately several University studies show (with photographs) and explain just why there is so much need to keep your blades sharp. Keep in mind that rotating blades have a machete-like action and must be sharp in order to cleanly slice grass blades rather than tear them.

How do your grass blades look? The University of Arkansas shows the affects of mowing with dull blades, and the damage caused:

(not sure if I'll be able to post the picture)

THE CUT THAT COUNTS
Images A, B, and C, show damage to grass blades from dull mower blades (ragged edges, stringy edges, etc.).
Image D-1, shows a good clean cut.
Image D-2, shows a stripe (just above the white numeral "2") indicating damage previously inflicted by a dull blade.
Images D-3 and D-4 show the ragged edge of a dull blade cutting.
(Cooperative Extension Service photos by Aaron Patton)

"My Five (or More) Year Old Blade is Good Enough" -
OK, let's presume (a) your total grass area is one half acre, or 21,780 sq. feet and (b) you mow once a week, or 20 times a season (more if you shred leaves). This equals 435,600 square feet (10 acres). Given the small 1/2 acre area you mow in this example, you most likely mow with a walk behind. Common widths cut by walk behind mowers are 19 inch, 21 inch and 22 inch - let's use the wide 22 inch figure. Therefore 435,600 square feet is the equivalent of a 22 inch wide strip that is approximately 237,600 feet long, or a strip 45 miles long that you mow each year. In five years, this is 225 miles and is about the distance from Boston to New York. Logic dictates the blade won't be as sharp in New York as it was when you left Boston! And mowing 45 miles each year without sharpening several times during the season is ill advised as your blade is becoming dull, you are wasting fuel (up to 22%), and allowing the vegetation to cling to your blade and underside of your deck promotes rust and shorter equipment life.

This ought to be enough for now ... and as a new user I may be required to post this in several posts due to its length ... we will find out.

WOW! Thanks for the PRO advice, all this time I thought it was just blades, grass and motors

RobertBrown said:

WOW! Thanks for the PRO advice, all this time I thought it was just blades, grass and motors

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:laughing::laughing: too funny... :smile:KennyV

Consider sending your flywheel, crank shaft, piston, and rod to a Pro for a balance check because in the countries where those parts were made they use a nail to balance.:laughing: OH, don't forget to send the rod cap screws.

wow lots of work how much you charge for all that

Doesn't matter today or yesteryear. Ever hear of blueprinting and balancing? Been going on for decades. In fact, in the 60s and 70s, British products were known to vibrate and leak oil - so much so that there was a saying: "If it doesn't vibrate or leak oil, it wasn't made in Britain".

briggs said:

wow lots of work how much you charge for all that

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Cleaning/Inspection/Sharpening/Balancing:
$7.00 for a single blade
$12 for a two blade set
$15 for a three blade set

If you bring us your equipment, we remove, perform the above service and replace the blade(s)
for:
$14 for a single, $24 for double and $30 for a three blade set.
All blades processed overnight using Magna-Matic equipment; all equipment lifted using Mo-Jack and or Titan 1500 XLT lifts; all blades anti-seized and torqued to manufacturer specs using electronic digital torque wrenches. We also loan tools for free (deposit required) to homeonwners so they can remove their blades without having to transport equipment. We also offer to LCs remote blade pickup/delivery service (6 blade minimum), while you wait service (extra cost), etc. etc.

CQ_DX said:

Doesn't matter today or yesteryear. Ever hear of blueprinting and balancing? Been going on for decades. In fact, in the 60s and 70s, British products were known to vibrate and leak oil - so much so that there was a saying: "If it doesn't vibrate or leak oil, it wasn't made in Britain".

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That brings back memories. In the mid- to late-60s I worked at a dealership that sold British cars exclusively. There was always a lot of cynical humor going around, most commonly about the electrical systems (eg. "God said 'Let There Be Light' but Lucas [British electrical component manufacturer] invented darkness.")

There was also a joke that if you really loved Jaguars you needed two since one was always going to be in the shop.

Two-Stroke said:

"God said 'Let There Be Light' but Lucas [British electrical component manufacturer] invented darkness."

There was also a joke that if you really loved Jaguars you needed two since one was always going to be in the shop.

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Lucas prince of darkness....

for Jaguars thats still true today... a friend of mine has hers in the shop more than out... :smile:KennyV