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Blade-balance oddity

#1

B

bullet bob

I bought a used Toro 21" self-propelled for my daughter. Among other things, I pulled the blade, sharpened it but when I went to balance it using my https://www.sharpeningsupplies.com/...8vIgSSCKYG-FFbB7tjnKVGrVH0G7DFqxoC47kQAvD_BwE
When the blade was completely horizontal, it showed a perfect balance. But when I moved the blade to almost vertical, it immediately went back to horizontal. Does this make any sense?


#2

R

Rivets

Makes perfect sense. Trying to balance something only 2” wide would be extremely difficult, so the blade wants to balance something 21” long. Someone called it physics.


#3

StarTech

StarTech

Besides one side of each end is heavier the other side on the same end. A good balancer can easily see the difference. The balancer I use is very sensitive to this mismatch weight. I am even finding new blades out of balance.


#4

B

bullet bob

I thought if something was balanced east to west, it would also be balanced north to south.


#5

StarTech

StarTech

Well it seems it would but the laws of gravity works differently. It would someone that studies this to explain why but I think it something to do how things attract and repel other each other.


#6

S

SeniorCitizen

My pocket knife blade dead centered on the hole doesn't have that problem . :ROFLMAO:


#7

J

Jimmy the Lock

So how do you guys bring a blade in to balance if it's out of balance?

Do you take a grinder and remove material off of the blade on the heavy side and keep testing until it's balanced?

I know ya'll can't be adding weight as you'd have to get a welder for that


#8

C

*CPB*

bullet bob said:
I thought if something was balanced east to west, it would also be balanced north to south.
Click to expand...

Then how would you know if it was ever out of balance?


#9

M

MParr

A 16d nail in a stud or tree works well.


#10

C

*CPB*

MParr said:
A 16d nail in a stud or tree works well.
Click to expand...

It works, but it doesn't work well. A nail is equivalent to a calculator that shows whole numbers only.


#11

F

Freddie21

If you have a heavier end and it is down when the blade is vertical, it won't move. If you put it upwards, it will rotate. Being horizontal, it will rotate either way. I have an 1\8 in rod protruding out of the edge of my bench that I horizontally balance the blades. It is level and plumb with the bench and works very well. A cheap cone type balancer did not work well for me, not accurate enough.


#12

StarTech

StarTech

Jimmy the Lock said:
So how do you guys bring a blade in to balance if it's out of balance?

Do you take a grinder and remove material off of the blade on the heavy side and keep testing until it's balanced?

I know ya'll can't be adding weight as you'd have to get a welder for that
Click to expand...
Exactly you remove material on the heaviest side until the blade balances.

Here is the balance I use that is mounted on the wall horizontally.
1709987102924.png
It cost me around $100 for the Oregon version but a clone can be gotten for as low as $34 off Amazon. But I prefer to stick with the Italian made one.

And before someone asks what the rod is for it is for checking bent blades and can be use for checking for off center blades when they are short enough.


#13

C

*CPB*

StarTech said:
It cost me around $100 for the Oregon version but a clone can be gotten for as low as $34 off Amazon. But I prefer to stick with the Italian made one.
Click to expand...

The Oregon version is a clone too. The Magna-Matic is the original.


#14

StarTech

StarTech

Yes it is but much better made than some junk Chinese clones or least mine is. Had tried those other ones and had to send several back.


#15

B

bullet bob

When I balance a motorcycle tire, once it is balanced it doesn't matter where the heavy part was. I can rotate the tire to any position and it doesn't move. Figured a blade should do the same........


#16

StarTech

StarTech

bullet bob said:
When I balance a motorcycle tire, once it is balanced it doesn't matter where the heavy part was. I can rotate the tire to any position and it doesn't move. Figured a blade should do the same........
Click to expand...
A completely different thing it is round object and mower bar blade are basically just a long flat length of metal.

A wheel is constant circle and gravity affects it differently for one thing plus once balance it be balanced in any position as any slight out balance is spread out along the entire circle where on a bar blade any slight out of balance is focus on one end or the other.

Personally I would just accept that this how things work and stop worrying about it. Too many other things to worry about like that we are headed to WWIII; at least we know WWIV will fought with sticks and stones if anybody is left.


#17

R

RevB

bullet bob said:
I thought if something was balanced east to west, it would also be balanced north to south.
Click to expand...
The earth spins east to west and wobbles. Is also an oblate spheroid that is squashed north to south. 🤫


#18

R

RevB

bullet bob said:
When I balance a motorcycle tire, once it is balanced it doesn't matter where the heavy part was. I can rotate the tire to any position and it doesn't move. Figured a blade should do the same........
Click to expand...
How often do you require your blade to be vertical. 🤔 Balance applies to the plane of rotation.


#19

C

closecut

*CPB* said:
It works, but it doesn't work well. A nail is equivalent to a calculator that shows whole numbers only.
Click to expand...
Is the hole in the blade round,or star or other shape?If not round,and perfectly centered your results will not be good.Use a level to check your tester with blade attached.Mark center of the level as precisely as possible.Check left to right across blade,and end-to- end.
A single nail in a post will offset the vertical (edge-to-edge) weight of the blade and give an error.
Computer balancing machines show placement of weights on both sides of tire to balance in 2 planes .
Good luck.


#20

S

schreib69

bullet bob said:
I bought a used Toro 21" self-propelled for my daughter. Among other things, I pulled the blade, sharpened it but when I went to balance it using my https://www.sharpeningsupplies.com/...8vIgSSCKYG-FFbB7tjnKVGrVH0G7DFqxoC47kQAvD_BwE
When the blade was completely horizontal, it showed a perfect balance. But when I moved the blade to almost vertical, it immediately went back to horizontal. Does this make any sense?
Click to expand...
The real reason why. . .
Notice your blade is NOT symmetric. It is bent in and towards the grass at the 3" long cutting edges and squared off on the "backside"-- at a different angle to the axis of the blade. This difference makes its weight different from one side(across the 2" face) to the other. So, when balanced vertically, even on a perfect knife edge, that difference pulls it easily off to one side with only 1" leverage from the center. Once started, it really moves and, I'll bet, nearly flips vertical again. If the blade had a perfect bend on both sides with symmetric cutting edges, it WOULD stay vertical.


#21

O

Oddjob

bullet bob said:
I bought a used Toro 21" self-propelled for my daughter. Among other things, I pulled the blade, sharpened it but when I went to balance it using my https://www.sharpeningsupplies.com/...8vIgSSCKYG-FFbB7tjnKVGrVH0G7DFqxoC47kQAvD_BwE
When the blade was completely horizontal, it showed a perfect balance. But when I moved the blade to almost vertical, it immediately went back to horizontal. Does this make any sense?
Click to expand...


#22

J

Jimmy the Lock

The blade is going to be spinning horizontally on the mower so seems like that would be the thing to focus on when balancing which should be a matter of trying to achieve equal weight distribution across the entire blade.

When you buy new blades, are they balanced at the factory?


#23

O

Oddjob

It is gravity. Maybe it would help if you think about objects floating in liquids, rather than being suspended in air, like you do when you attach the blade to your balancer. If you threw a two by four in a pond it would float horizontally, not vertically, unless you attached an even heavier weight to one end. Everything is being pulled to the center of the earth (not counting the much lower gravitational pull of other heavenly bodies, like the moon and sun). Your balancer is set up plumb, in other words, in alignment with and pointing at the center of the earth. The cone on the balancer aligns the blade so that its center is perfectly centered (assuming the blade was correctly manufactured and that the blade hasn’t been deformed). The bearings allow the blade to react to gravity without falling to the floor, just like the pond water allows the 2x4 to float horizontally as gravity evenly pulls it to the center of the earth. The higher density of the water prevents the wood from falling below the water’s surface. An out of balance blade has two uneven halves. The one with the greater mass is pulled with greater force by gravity than the one with less mass, leaving the heavier half pointing to the earth’s center. Balance the masses of the halves and you have a blade that ”floats” like a uniformly dense piece of dimensional lumber on a calm water surface.


#24

J

Jimmy the Lock

Oddjob said:
It is gravity.
Click to expand...

Yes, and if the blade has equal weight distribution across the entire blade then it should be balanced and spin smoothly without vibration.


#25

D

Davenj4f

bullet bob said:
I bought a used Toro 21" self-propelled for my daughter. Among other things, I pulled the blade, sharpened it but when I went to balance it using my https://www.sharpeningsupplies.com/...8vIgSSCKYG-FFbB7tjnKVGrVH0G7DFqxoC47kQAvD_BwE
When the blade was completely horizontal, it showed a perfect balance. But when I moved the blade to almost vertical, it immediately went back to horizontal. Does this make any sense?
Click to expand...
I balance every new blade I buy. One in twenty might be close enough to use. I user a $200 balancer. I balance tip to tip, like you do. But sometimes, the center hole is off center, rarely, but enough to make the edge of the blade at the hole heavier on one side. I've never had it off enough to matter, but a few times, for the fun of it, I would grind a little bit off next to the hole, and get the blade very balanced. But the mower never seemed to notice.


#26

C

*CPB*

Jimmy the Lock said:
When you buy new blades, are they balanced at the factory?
Click to expand...

I've never seen a new blade that was balanced. Maybe it'd be if it was hung from a nail, but not on my balancer.


#27

J

Jimmy the Lock

Davenj4f said:
I would grind a little bit off
Click to expand...

So how much grinding is typically needed to get one to balance?


#28

StarTech

StarTech

Just depends how bad it is out balance due to wear. Some it a little and other it takes a lot. Even new blades are sometimes out balance according to my balancer. You first correct cutting edge and then sneak up getting them near prefect balance by grinding the heavy end further while keeping about a 35 degree cutting edge angle.

But i hate try to sharpen those 1/4 thick blade as they can up to 30 minutes to correct them.


#29

G

Gord Baker

bullet bob said:
I bought a used Toro 21" self-propelled for my daughter. Among other things, I pulled the blade, sharpened it but when I went to balance it using my https://www.sharpeningsupplies.com/...8vIgSSCKYG-FFbB7tjnKVGrVH0G7DFqxoC47kQAvD_BwE
When the blade was completely horizontal, it showed a perfect balance. But when I moved the blade to almost vertical, it immediately went back to horizontal. Does this make any sense?
Click to expand...


#30

G

Gord Baker

bullet bob said:
I bought a used Toro 21" self-propelled for my daughter. Among other things, I pulled the blade, sharpened it but when I went to balance it using my https://www.sharpeningsupplies.com/...8vIgSSCKYG-FFbB7tjnKVGrVH0G7DFqxoC47kQAvD_BwE
When the blade was completely horizontal, it showed a perfect balance. But when I moved the blade to almost vertical, it immediately went back to horizontal. Does this make any sense?
Click to expand...
Yes. It will be fine. Run it.


#31

A

aussielawny



#32

Hammermechanicman

Hammermechanicman

I wonder how well the blades with star holes balance on a nail

🤣🤣🤣


#33

M

MParr

Hammermechanicman said:
I wonder how well the blades with star holes balance on a nail

🤣🤣🤣
Click to expand...
Use a bigger nail or a cheap Arnold balancer. 😜
It was balanced in the horizontal position. That’s good enough.


#34

C

*CPB*

They make inserts for blade holes that aren't round


#35

R

rhkraft

If your mower blade is magnetized, it could depend on close you are from the north or south poles where magnetic dip may be sensed. Or if the blade is quickly accelerated or decelerated along a latitudinal or longitudinal plane turning error may occur as in a compass.


#36

J

Jimmy the Lock

So when will they come out with carbon fiber blade with diamond cutting edges that never need replacing?

Seems like they could tell Brutha AI to whip these out for a reasonable price, and balanced of course! thumbsup2.gif


#37

G

Gord Baker

rhkraft said:
If your mower blade is magnetized, it could depend on close you are from the north or south poles where magnetic dip may be sensed. Or if the blade is quickly accelerated or decelerated along a latitudinal or longitudinal plane turning error may occur as in a compass.
Click to expand...
Ya and the sky is falling.


#38

D

davis2

Do they need to be absolutely perfect? The first time you hit a rock or other object is likely to throw it out anyway. I'd say get it good and close so there isn't vibration. But it really isn't absolutely critical to be perfect... Now I understand some of you are being sarcastic ( please continue) but we aren't talking about intricate stuff... Carry on, just my $.02


#39

C

*CPB*

If you hit something why would you keep using the blade without either fixing or replacing it?


#40

D

davis2

I'm not talking boulder... Small stone, maybe something else... You may never know... Who mows without something finding the blades that isn't grass?


#41

C

*CPB*

That's true, but very rarely on my own lawn. There aren't any stones in the yard, and if I hit a stick it's almost always smaller than the diameter of a pencil so it just gets obliterated (it's also dry and dead, from the tree that's slowly dying. I pick up a few larger sticks once a week). When I pull my blades there are usually some tiny nicks, but nothing that would make them out of balance. I've been sharpening and balancing blades long enough to have come to the conclusion that there's a window of what I consider balanced vs. needing to be balanced. 100% perfect isn't any better than virtually perfect.


#42

H

hlw49

I have a Magna Matic and it balances horizontal and turn it vertical it will go back to horizontal. Never really though about it but tried it when this post came up. Seems funny but that is the way it works.


#43

G

Gord Baker

The blade spins at high RPM. About 3,000. A slight out of balance is irrelevant.


#44

D

davis2

What I was thinking. As long as there is no vibration, should be ok... I think some of the posters expect balance weights down to the gram!!!


#45

M

MParr

davis2 said:
What I was thinking. As long as there is no vibration, should be ok... I think some of the posters expect balance weights down to the gram!!!
Click to expand...
I don’t get super picky. Mower blades aren’t precision instruments.


#46

C

*CPB*

It's not about the blade, it's about the spindle it's attached to.


#47

A

aussielawny

MParr said:
I don’t get super picky. Mower blades aren’t precision instruments.
Click to expand...
Yep, common sense needs to be applied - we're not conducting brain surgery......


#48

S

SeniorCitizen

*CPB* said:
It works, but it doesn't work well. A nail is equivalent to a calculator that shows whole numbers only.
Click to expand...
OMGAWD


#49

StarTech

StarTech

davis2 said:
What I was thinking. As long as there is no vibration, should be ok... I think some of the posters expect balance weights down to the gram!!!
Click to expand...
No I don't expect prefect balance but it is a lot closer so less wear on bearings and less noticeable deck vibration.

And with the balancer I now use it is a lot closer as it is a lot more sensitive than the old cone balancer and way more accurate than try to use a nail which is usually off center.


#50

S

SeniorCitizen

If you'll buy me a plane ticket i'll take that blade to Denver and get it balanced . If they can't do it Paris i believe is the next step up . :ROFLMAO:

Best 6 Crankshaft Balancing in Denver, CO with Reviews

Crankshaft Balancing in Denver on YP.com. See reviews, photos, directions, phone numbers and more for the best Crankshaft Grinding in Denver, CO.
www.yellowpages.com www.yellowpages.com


#51

C

*CPB*

SeniorCitizen said:
OMGAWD
Click to expand...
What's the problem? It was a great analogy.


#52

G

Gord Baker

I can balance it here in SWO for $3,856


#53

StarTech

StarTech

Just to show how sensitive these ball bearing type balancers are.

Before
1710169309397.png
After a small paper clip added to light end.
1710169415842.png
My gram scale won't even register its weight so the clip is well under a gram. And that is probably just a variance in the paint thickness.
So yes it very sensitive and actually over sensitive for mower blades.


#54

R

Rivets

Star, what is the part number for those bottles sitting on your spare parts shelf?


#55

Hammermechanicman

Hammermechanicman

Gord Baker said:
I can balance it here in SWO for $3,856
Click to expand...
Where is SWO?


#56

E

efred

*CPB* said:
It works, but it doesn't work well. A nail is equivalent to a calculator that shows whole numbers only.
Click to expand...
I use a stepped cone-style balancer.

Hey, have any of you noticed that NONE of the alignment steps in those balancers correspond with ANY hole in any blade?


#57

StarTech

StarTech

Rivets said:
Star, what is the part number for those bottles sitting on your spare parts shelf?
Click to expand...
Stop licking your lips Rivets, they are not available as they contain home made 20 proof Muscadine, 20 proof red plum, and 20 proof wild native plum wines in two liter bottles. Since I don't drink I use them for cooking only. They make some really good tasting boneless pork chops and pepper stir fly steak.
efred said:
I use a stepped cone-style balancer.

Hey, have any of you noticed that NONE of the alignment steps in those balancers correspond with ANY hole in any blade?
Click to expand...
Yes that is why I got away those type balancers.


#58

C

*CPB*

StarTech said:
My gram scale won't even register its weight so the clip is well under a gram. And that is probably just a variance in the paint thickness.
So yes it very sensitive and actually over sensitive for mower blades.
Click to expand...
I tell people who watch me balance their blades that goal isn't to have the blade be 100% motionless when it's on the balancer, just to move very slowly.


#59

D

davis2

StarTech said:
No I don't expect prefect balance but it is a lot closer so less wear on bearings and less noticeable deck vibration.

And with the balancer I now use it is a lot closer as it is a lot more sensitive than the old cone balancer and way more accurate than try to use a nail which is usually off center.
Click to expand...
I have the old cone. I try to get it as close as I can, but some seem to want perfection. I've done well, but am far from perfect. But I get a nice mow, and haven't ruined anything yet...


#60

S

ss63

bullet bob said:
I bought a used Toro 21" self-propelled for my daughter. Among other things, I pulled the blade, sharpened it but when I went to balance it using my https://www.sharpeningsupplies.com/...8vIgSSCKYG-FFbB7tjnKVGrVH0G7DFqxoC47kQAvD_BwE
When the blade was completely horizontal, it showed a perfect balance. But when I moved the blade to almost vertical, it immediately went back to horizontal. Does this make any sense?
Click to expand...
Hello been working on mowers / engines since I was 7 now 70 and worked in a mower shop from age 13-21 ok been balancing blades on a nail on a shelf you just do horizontally left the right invert then left & right on this side Then flip & do the same The blade needs to be level strate across 9-3 o'clock position Then grind the heaver side till level flip to see the same level Been doing this for years ! hope this helps


#61

R

Rivets

Was hoping for a part number, because some days on this site I could use a bottle. If I gave you my model and serial numbers could you find me a part number?


#62

D

davis2

Rivets said:
Was hoping for a part number, because some days on this site I could use a bottle. If I gave you my model and serial numbers could you find me a part number?
Click to expand...
They are different at all liquor stores...


#63

Hammermechanicman

Hammermechanicman

I heard alcohol kills germs. I am doing my best to prevent the flu.
😉


#64

StarTech

StarTech

Rivets said:
Was hoping for a part number, because some days on this site I could use a bottle.
Click to expand...
You and me both...but I don't like waking up not knowing where I am.

But you could always be like me. I slept with four gals last night. Now they were in my hand all night wrapped up in a towel as they would not shut up otherwise.


#65

B

bertsmobile1

efred said:
I use a stepped cone-style balancer.

Hey, have any of you noticed that NONE of the alignment steps in those balancers correspond with ANY hole in any blade?
Click to expand...
Yes so I turned up a new cone


#66

S

SeniorCitizen

If anyone needs a blade more balanced than grams , I have a antique powder scale i can get a blade to balance withen 5 grains . Postage pre-paid both ways .


#67

S

slomo

RevB said:
How often do you require your blade to be vertical. 🤔 Balance applies to the plane of rotation.
Click to expand...
Never thought of that. Perfect sense.


#68

S

slomo

davis2 said:
I'm not talking boulder... Small stone, maybe something else... You may never know... Who mows without something finding the blades that isn't grass?
Click to expand...
All the young people. Old timers never had this issue. They would walk the yard prior to mowing. Wisdom at it's best.


#69

D

davis2

slomo said:
All the young people. Old timers never had this issue. They would walk the yard prior to mowing. Wisdom at it's best.
Click to expand...
I do walk the yard, but sometimes miss something or get too close to the stone driveway. I've heard many old timers mow their stones...


#70

StarTech

StarTech

Here they mow the asphalt and tree roots along with the concrete sidewalks.


#71

D

davis2

StarTech said:
Here they mow the asphalt and tree roots along with the concrete sidewalks.
Click to expand...
Haha... You guys are funny! 🤣 I know you see the worst of the worst as repair techs. But as you know, my point is that you don't see everything even when you do it all right. But those damn weeds, they just tease me!!!!!!!


#72

Avman

Avman

aussielawny said:
Click to expand...
I love my Mag 1000. It will balance to a nat's ass.


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