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Stone wheel=bad


Sam Salvati

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I took my old pedal powered stone sharpening wheel and hooked it up roughly to my belt grinder motor, set on the middle speed pulley configuration, it was running smooth and true. I put a piece of steel to the wheel while it was running, I was off to the side not sitting on the seat. If I had been sitting in the seat I would either be in the hospital in a vegetative state from a crushed in skull or laying in a bed with massive blunt trauma, or dead laying in my shop until someone found me. The stone exploded, and when I say exploded I don't mean it came apart I mean it exploded with a bang, broke into 4 main pieces and in line with how it was spinning. 2 small chunks went through my roof, 1 chunk went through my small ryobi wood bandsaw and embedded chunks of stone and the bandsaw itself into the 2x4 shelf beam behind it, another main chunk flew into my KMG motor which was powering the grinder and put a 1/2" deep 2 1/4" round dent into it and broke off the magnet inside and pulverized the wireing box on the front, the other 2 main chunks and small bits went into the wall and pulverized. A split second after it exploded I went running out of the shop, seeing the directions and sizes of the pieces after the aftermath I was lucky I was not hit by a ricocheting piece that could have seriously damaged my body or killed me. In hindsight it did not seem that stupid an idea, but thinking deeper a natural sandstone(?) wheel as compared to the vitrified wheels that run just fine 3 times as fast on my bench grinder was not a smart idea. If you own one of these grinders, do not attempt to motorize it. I thankfully made it through this event unscathed, but it could have been worse in more ways than it could not have.

 

I am talking about this type of grinder

 

http://c2.ac-images.myspacecdn.com/images01/55/l_b8551efed9b27a09f25c392f2aaea6bd.jpg

Edited by Sam Salvati

Let not the swords of good and free men be reforged into plowshares, but may they rest in a place of honor; ready, well oiled and God willing unused. For if the price of peace becomes licking the boots of tyrants, then "To Arms!" I say, and may the fortunes of war smile upon patriots

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I am really, really glad that you're alright.

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Yikes!:blink: that is something to add to the "tell my psychiatrist" list.Glad your ok.

Edited by Isaiah Lake

The extraordinary has never been achieved without the sacrifice of security. Take your chances thin, and take them often.

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As with all the others, I am happy that you walked away with merely soiled undershorts. But trying to motorize any handtool is usually a bad idea, and you just discovered why. Sorry about the loss of a good item, too... and your bandsaw and intact roof.

The Tidewater Forge

Christopher Price, Bladesmith

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There are stories told of the huge stone wheel grinders of Europe unlimbering from their mounts and wandering through town wreaking havoc.

 

Makes a 36 grit 72 inch turban look pretty tame...

There are three kinds of men. The one that learns by reading. The few who learn by observation. The rest of them have to pee on the electric fence for themselves. Will Rogers

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Seriously glad to hear your alright Sam.

 

We've contemplated doing makeshift tools like this as well.

Thanks for the reminder to stay safe.

I do not love the bright sword for its sharpness, nor the arrow for its swiftness,

nor the warrior for his glory. I love only that which they defend"

J.R.R. Tolkien

 

 

www.CedarloreForge.com

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Glad to hear that you didn't loose anything that can't be replaced. I bet you lost some of the starch in your knees for a while, I know that I would have.

 

Doug Lester

HELP...I'm a twenty year old trapped in the body of an old man!!!

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Wow. Glad you escaped with your life and limbs.... I guess one of Johns big contact wheel machines is in order eh? Is that what you were trying to do?

BTW that is what happends when you try and run those abrasive cut off/ grinding wheels over their recommended speed also.... One of my best friends nearly lost his hand when one of them blew up on him...

So that was an exspensive lesson Sam. Glad you are OK. and thanks for being humble enough to share it ....

 

now that you adrenalin is back to normal could you take some photos of the damage?

Dick

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I am glad you are alright. I usually have a last minute warning from my jinn saying, this is not a great idea. We have to think of all the possibilities when we are working alone. Good lesson.

 

Don

Don Fogg

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I'm glad you're doing fine and I really appreciate you sharing about what happened. It really didn't seem that dangerous of a thing to do and honestly I was planning to that with a large grinding stone myself. You've probably saved me a few critical appendages and it certainly makes me think twice about any new ideas and safety.

Wes Peterson

 

www.wpbladesmith.com

Southeast Georgia

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Yikes. You know, I've read that stones undergo lots of internal stresses, but it's one of those things that's a little hard to get your mind around. I mean, rock is strong stuff, right? But if I have the math right, doubling the diameter of a wheel while keeping everything else constant means that the forces it experiences increase by a factor of 16. It's not hard to see how that can get out of hand fast.

 

Glad you're safe, Sam.

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Glad you are ok. Too bad it cost you some tools, better them than you.

Ben Potter Bladesmith

 

 

It's not that I would trade my lot

Or any other man's,

Nor that I will be ashamed

Of my work torn hands-

 

For I have chosen the path I tread

Knowing it would be steep,

And I will take the joys thereof

And the consequences reap.

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Thanks everyone for the kind words.

 

Dick, sort of. I was just trying to power the old stone grinder.

 

Jake, luckily the stone peice only bashed in the motor, even being only 6-7 inches away from the impact point on the motor the KMG itself did not suffer any damage at all, so all i need is a new motor.

 

 

Matt, it makes perfect sense now. The larger the outer diameter gets, the more stress it is under from centrifugal force, the inner area of the stone most like was getting pulled apart by the outer area's forces, causing it to explode like it did.

Edited by Sam Salvati

Let not the swords of good and free men be reforged into plowshares, but may they rest in a place of honor; ready, well oiled and God willing unused. For if the price of peace becomes licking the boots of tyrants, then "To Arms!" I say, and may the fortunes of war smile upon patriots

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Slow rpm on big stones, old, new, natural, synthetic. The bigger the diameter, the less rpm. Glad you didn't catch a piece of it with your body, Sam. :)

 

Sifu said:

I am glad you are alright. I usually have a last minute warning from my jinn saying, this is not a great idea.

 

The trick is in learning to listen, is it not ? :)

Edited by Howard Clark
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Matt, it makes perfect sense now. The larger the outer diameter gets, the more stress it is under from centrifugal force, the inner area of the stone most like was getting pulled apart by the outer area's forces, causing it to explode like it did.

 

Yup, although on second thought I think it's a factor of 8, not 16. Anyway, it's enough! Again, glad you're safe.

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Damn Brother! Thank goodness you were standing on the side of it.

My life is like shaving with a razor sharp machete. It's a bit awkward and I feel a sting every now and then, but in the end I'm happy with the results.

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One of my teachers has a story similar to that, but not with such a happy ending.

He bought some old factory made grind wheels at a garage sale and put them into position on his grinder...they flew apart and his wife found him later just standing there in place in front of the empty still turning shaft with just a little blood on his forehead. He never got better.

 

One needs guards in place for such things.

F=MxA

 

Ric

Richard Furrer

Door County Forgeworks

Sturgeon Bay, WI

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