Metal Cutting Disc Exploding 13 000 RPM | This is Why You Shouldn't Remove the Grinder Guard! 

As a welder, I would like to see some welding leathers over one of the melons when the disc explodes.

I was involved in an incident like this. We all had the guards off because they were “in the way”. One of the guys had a wheel explode and hit him in the neck. I got to help control the bleeding by pushing in on the cut to keep him from bleeding out. Changed careers and now I’m the safety guy at work. Use the damn guards!!!

the shaft definitely made it fail prematurely. It likely would do more damage if it were balanced and broke under it's own force

Important safety lessons: Never remove grinder guard Know proper PPE (glasses vs face shield here) Never be a watermelon on RU-vid, especially if slow motion filming is involved.

I have great respect for the energy stored in rotating stones. I was a young man working in my dad’s company running an OD-ID grinder. We would grind these parts that had a 4” foot (half of a flange) and 3” body 15” long. The grinding wheel was 24” in diameter with a 3” face. We would grind the body and come up and just “kiss” the foot as the part moved back and forth. You had to get right up there to see what you’re doing. I had done this many times but this day I was needed on another job. I hear a loud crash and an ungodly vibration. What had happened is the stop had failed and instead of the wheel cycling up to the foot it continued on to the corner. The wheel grabbed the part sheared the drive center and threw the part right over the operator’s shoulder just missing his head. The part flew across the shop (80’) and punched a hole in one in the hollow spaces in a cinder block wall. A large chunk was taken out of the wheel which caused an imbalance that made the big machine shake so violently that it started to walk across the floor so far that mercifully it pulled the power conduit out of the wall killing the power. The operator was white as a ghost. We were about to bid on another run of the same parts and I was probably going to run the parts. I looked at my dad and said “Don’t you like me?” He no-bid the job and sold the machine.

The watermelon looks so COOL wearing those safety glasses

Another great Public Safety film from the coolest couple on RU-vid.

If a Finn says "don't try this at Home", dont try this at Home!

When both of them wear winter clothes, you know that it´s really, really, really cold outside.

It's like they are investigating a crime scene.

I’m watching all ads in full length so Anni and Lauri can afford to buy new windows to Timo’s workshop

Ladies and gentlemen, the King and Queen of, "Don't try this at home!"

Do a wire wheel so we can see high speed needles flying in high speed. How much damage they can do.

I lost partial use of a finger from a cutting disc while cutting pipe. Very dangerous. Great video!

Dude, you nailed "ricochet"!

Be careful guys. This was probably one of your most dangerous projects. Fascinating.

"oh no the tool is broke!" that's not the first time you've said that :)

That shows you need to safety squint even when wearing those glasses

I think the cat has put on some weight to stay warm for winter. Gotta keep warm.

At about 5:55 we've seen "that look" from Anni on some other videos. This time it was very quick to the camera, but we all know what she meant. 😱

What we learned: safety glasses are dangerous when using a grinder 😂

Keep on doing these videos with multiple plausible scenarios. These are great for safety lessons, specially on those people who say "nothing has ever happened to me, it's ok".

I had a 1"(2.5cm) dremel cutting disc explode about 1.5ft from my face at 60krpm. Full face shield caught about 70% of the shrapnel, the other 30 was spun out the other direction. Biggest piece halfway penetrated the shield right on front of my right eye. Missed blinding me by about 1/2 inch. I still got dust and other crap in my eye from the penetration. Luckily the eye doc was able to get it all out within 20 minutes with no cornea scratching. Now i double up, lenses under shield, when using rotary cutters.

i haved injured two years ago - cutting disk explode when i cutted steel tube - big cut on left hand now... Take care and be careful at everyday work! You and your wife make great videos!

"The goggles, they do nothing!"

What I've learned: there's a 1 in three chance to survive an exploding disc with only minor scratches :-(

Mental note to self - never grind with a router!

So, i didnt believe the speed he said it flew at at first. Sounded way to high. So did some math on my own, assuming the thing has a diameter of about 20 cm and going at 13000 RPM... the speed he gives is completely reasonable and realistic. Holy shit thats fast.

God I love this channel. Consistently high quality videos which are educational to an extent. Y’all are doin something right.

1:31- The best *Preety Gud* I've ever heard, listened to it 4 times 😂

I'm glad you guys are taking your safety extremely seriously with this one, and not just standing behind some plexiglass.

Yalls English is a really getting better. When I first started watching it was hard to understand alot he was saying but now they are seasoned youtubers.... ;-)

9:38 Lauri told us the shrapnell are going 450 km per *second*. Perhaps you can fix it until tomorrow? Great Video again, the bunker plus router have a great potential :D I think I would like to see a wooden disc shatter :) Or a frisbee or a plate or.... maybe the Propeller from a Ventilator?

9:36 Kilometers per hour* If it was going 450 kilometers per second I think you found your ticket to Mars.

one of the best random channels ever... somehow they manage to be so instructional on safety measures.

E xcellent safety video. I have had patients that were injured by exploding discs. Deep penetrating wounds. Lots of deep tissue and organ damage. thanks for taking the time to make this video

How lucky, or unlucky, that the disc broke in exactly the right moment to hit the watermelon with the safety glasses.

That bunker would make a nice pool. You just need one more wall. You could shoot under-water videos there.

I got an ad for safety glasses on this vid. Pretty fitting, I think!

You could turn this video into a public service announcement. Really shows the danger of removing guards on equipment. Thanks for sharing.

In the U.S., it’s recommended to wear Z87+ safety glasses as well as a face shield when using a cutoff wheel and grinding wheel. Check out the pics of people online that didn’t! 😳

2:38 We know everything is going to be OK, Nelli the Safety Cat is on the job!!

So fast and brutal it will turn your safety glasses into safety contact lenses!...

Hi Guys greetings from Australia. As a mechanical fitter and machinist for over 35 years I'll say that this would make along with part 2 very good safety video's for industry. Well done guys and good call on using the bunker.

the monochrome footage when the disc liquefies is awesome.

I used to watch your vids because I get a kick out of your accent. But you make damn entertaining stuff and you and your wife seem like good people.

Tjenare på er! Jag gillar era experiment big time! Jag gillar att ni gör de här sakerna tillsammans, jag önskar att ni får ha kärleken tillsammans länge! 🤘🏼🤘🏼🤘🏼🤩

9:58 “I think I was almost right.” Whenever I say that near my wife, she kindly reminds me that another way of saying that being almost right is being wrong. LOL!! I’m not going to argue with her!!

At the end of the video there is a little mistake in the math: 125 meters per second is 450 km/hour .... Not per second.

A great video to show my new students about to enter a workshop!

I had those shatter on me before luckily I was wearing a safety shield, it still cracked the lens. So I always use the shield on grinder. This is a good safety video!! Good job!!!

when i finish my presentation: everyone: -_- beyond the press: pretty good!

I'd love to see this exact thing again but where the wheel fails and not where the tool itself fails

Cool video , cold weather gear ok winter's coming around negative 20 Celsius this evening in Edmonton Alberta Canada .having fun watching your videos

Glad y'all are safe doing this

"Hey John, what are you doing today?" ... "Ohhh nothing, just gonna hang out in my concrete bunker with some water mellons."

7:16 Yeah, the grinder disc broke after it got out of balance because of a slight wobble that escalated. It ripped apart right at the mounting point.

Those high speeds are amazing!

look carefully at the hi-speed. the shaft is failing and changing the plane of rotation which the centrifugal forces are trying to resist until the shaft bends so much the center of the wheel buckles and fails. Pretty G00d!

I had a die grinder cutting wheel explode on me and hit me in the chin. The chunk of wheel cut to the bone where it hit and ran a line up my jaw where it then bounced of the ceiling hitting a wall 30 feet away then bouncing back across to land at my feet give or take a foot. I asked my friend is it bad he looks at it and says no it's not that. I look in the mirror and it truly wasn't too bad. Lol it could have been about an inch lower and slit my throat.

Epitaph: Tried it at home.

I'm definitely envious of your relationship. You guys are a great couple and it's just fun to watch

A friend of mine almost lost his index finger this way. Very informative video guys!!!

The 'spindle' was your cause of failure. As you say you need to make a better one and retry this test. I think the damage would be worse once that's corrected as the disk would then be spinning faster before it broke. Enjoy these vids.

Should've put a pair of jeans over one of them, really interested how easily is phases through denim

Safety First! Hey, when do you do your long truck trip livestream? (Kuusamo??) I want to be sure to catch at least some of that. Your last truck livestreams were great, felt like I was in the back seat driving to your live show! Amazing technology these days!

This happened to me too. With a 9 inch grinder .The guard was on & i had good fully enclosed saftey goggles also a cloth face mask, nevertheless my lower face & mouth was tottally numb & i dare not look in the mirror, i thought my teeth had surley gone. I was ok though & gradually the feeling came back into my lips & face. ALWAYS wear the right gear, i would definitely had lost my sight without it, even though the guard was on. This can happen when a CUTTING disc is used for grinding thus weakening the side of the disc, also dont use a damaged disc however slight the damage, also these discs have a shelf life , do not use an old disc. Thank you for this video warning people, good job!

Could you test a full face mask with a cutting disc for a small grinder? I'm just really curious to see if it will make it through.

"The safety glasses, they do nothing!" -Is it a good idea to microwave this Show

the 2nd extra slow motion replay had such low frequency bass that my whole house shook haha!

At 7:48 you can really see what destroyed the disc - the spindle was already distorted and had some extreme shaking. You can see the spindle bumping from one side to the other and back in 2 frames - easily a jump of 2 cm - given the timestamps that is at ~3000 FPS, so about 60 meters a second average speed, and a couple TENTHOUSAND Gs of acceleration. You can also see that it is only the spindle that is rocking that hard, so it was no longer attached to the disc. And then the disc is off centre and the spindle starts bending, digging right through the disc.

Intense. Try a stone grinding wheel as well. Thanx.

It looks like from the high speed that the tool or shaft bent and thats what caused the disk to fail.

You folks are very entertaining.

Also, I think the wobbling at the end really made a difference--you can see that the entire disc flies right into the glasses as it breaks from the middle, further breaking apart as it hits the glasses. I think this will be the most extreme result, as I doubt a more balanced disc will send that much mass all in one direction.

Test chainsaw chaps and facemask. Specifically made for safety from broken chains.

It was so deadly it destroyed the router and Lauri’s plans.....

When you pulled that piece of the safety glasses out of the water melon 🍉 wow that is scary. To think what could happen if that was person. Excellent video. Thank you.

I almost put a carbide tipped circular blade rated for 5,500RPM into a 22,000RPM cutoff tool because someone put it in the wrong pile. Glad I decided to check the rating before I powered up!

My uncle had on of these grinding disk blow up a cut his foot in half there is still a piece of the disk stuck in the wall of his shop. Be careful

"Prrrrrreetttttiiie goooooood"

"Ole Crabby". A man I use to work with was a welder. The first thing he did was remove the shield on his grinder. He had 1 finger and thumb on his right hand. When I first met him he had 3 fingers and thumb on his left. When I left that job he had 2 fingers and no thumb. Yea... shields good. Thank you for showing this.

Deadly thank you I learned something . Have had one selfdestruct didn't know how lucky I was

That's funny watermelon with glasses.

Is it me, or does it look like the thing that breaks the grinding wheel is the bolt bending?

You tease!!!! Cutting off the intro right before mass watermelon destruction. Lol.🤪👍😎 Good thing I watch your whole videos anyway!

So Dangerous.... *SO DANGEROUS!!!* You guys stay safe... Keep your eyes and fingers...

And for today's extra content...

Why wear safety glasses buddy was cutting his exhaust wouldn't put glasses on stoped him made him put them on shit u not 1 mins later back into cuting the whell exploded

More RPM- Vids please!!

Hey beyond the press Lauri and Anni Vuohensilta! Can you calculate the actual rpm using the high speed footage instead of just assuming it reached 30 000 rpm? Thank you for the wonderful video! Ride ride ride!

Makes me want watermelon

I have been waiting for this video since a very long time👍 cooooooooool

I think it was a complete misbalance, then the rotation force with the slight bit of movement from the motor helped unbalance it further until the core rod that connects the disc to the motor just started to bend with all the forces then the disc shatters, Who rpm does a car wheel do, maybe bolt the disc on to the wheel at the driveshaft and see how fast till it blows, i knew of a 1.6 fiesta that was customized that has room for this mod lol Thank you for your videos, very enjoyable

father lost most of the vision in his non dominate eye from a hand held cut-off disc exploding like this, doc said it was the equivilant of getting shot in the head with a .38, lost a good portion of memory from prior to then but healed to get a decent portion of vision back after all was healed, he layed in bed on his stomach to heal his eye for 5 months and still has issues with parts of the abrasives, wheel binders and glove material coming out of his eyelid every now and again, still has extreme sensitivity to light though, but he wants to warn people to not cut with the guard off of the cutter no matter what material you're cutting or the cutting disc is made of

Yes, we in the worksite are also greatful of those steel covers attached to all sorts of grinding gear. Every now and then you hear a loud bang and stop to see your grinding disc missing a piece, and thank the lord of these safety precautions. Wear those eye protecting glasses though, stay safe!

This is also why you should absolutely never use a cutting disc as a grinding disc; as far as I know, that's what causes a lot of those discs to explode during use. And never use them if they're damaged either. It's surprising how dangerous fairly common tools can be, really.

Very cool video Lauri/Annie,that grinding wheel really made a mess of things in no time!. I was thinking how to make things even more interesting... How about spinning a boomerang at 30,000 R.P.M.and see what it does when it's released??.

That router is doing a cute little dance in slow motion.

Yikes! Scary demonstration! Very sobering results! :O