And this, boys and girls, is why we wear PPE

[JHCC]

And don’t take the guards off our angle grinders!

[Irondragon Forge ClayWorks]

Been there, done that many times in my lifetime, every time it has happened the PPE and tool guards have saved my bacon.

[pnut]

Yep, if you use a cut off wheels enough you're bound to have some fail. The guards are there for a reason. It didn't get you did it?

Pnut

[JHCC]

No, the guard deflected it all in the other direction

[Frosty]

You really had me going there John! When I read the subject and saw you're AVATAR I opened the post expecting to see blood, protruding bone, maybe parts stuck in you. 

WHEW! Disk grinders are dangerous as heck when everything is going well but every now and then a blade cuts loose. Cut off wheels break all the time, they're thin and are basically zero kerf saws so even the slightest misalignment and they can jam and snap. 

In the . . .(had to take my shoes off there) 50 years of using disk grinders I've had 2 grinding disks break. One because I was using it to cut slots like it was a cut off disk ad it jammed and launched the 9" Milwaukee disk grinder across the shop after pulling part of my finger through the slot. My bad, no excuses.

The other grinding disk that broke had been dropped by one of the other guys using the shop. He didn't change the disk out or say anything to anybody, another shop slop kind of guy. My welding jacket prevented damage other than a few sq. inches of bruise on my ribs ad inside of my arms. It was like a bomb going off, my ears were ringing when I went to bed.

I can't count how many times I've had cut off wheels break in use. I really REALLY don't like the things but . . . <sigh> 

PPE RULES!!

Frosty The Lucky.

[arkie]

I had a 1/16" x 4 1/2" cut off disc fly apart on me (guard on grinder) once.  Found one piece next to the workbench...found the other (bigger) piece on my way from the shop to the house for lunch....some 25 ft. away!

[Daswulf]

Never had a wheel blow up. I Am always cautious. Wear ppe when using them and always use the guard. Prime example of what Can happen. And if the tool falls with the disc, Replace it! Not worth the unknowns with the risk already there and the wheels cheap comparatively. Also inspect your new discs.  Glad it didn't get you John. I throw away any suspect or risky disc. 

[Buzzkill]

I've been using the diamond edge cutoff wheels more lately.  They are only about 10 times as expensive as the "standard" abrasive cut off wheels, but they don't shrink as you use them and they don't turn into flying shrapnel without warning.  For me at least they tend to last more than 10 times as long as the other wheels too.  I still leave the guards in place and have eye protection when using them though.

[Glenn]

Each time when starting to use a grinder, let it run at full speed for a minute or so while staying out of the plane of the disk. If the grinder was dropped or the wheel cracked before you used it, the running at full speed can show vibrations or allow the disk to explode out of harms way.

If that disk in the photo installed upside down?  I thought they were suppose to be label up or toward the motor.

[Stash]

Wow, glad you're OK John. Definite code brown moment there. I've been using the diamond discs for a while, and have been pleased with them.

Steve

[Irondragon Forge ClayWorks]

Every recommendation I have seen is to install the wheels with the label facing out as JHCC has his so the information is visible as to speed, type etc.

[arkie]

Labels on discs are NOT uniform...you have to mount the disc(s) correctly depending on the type of disc, i.e. Type 27, and the type and orientation of your retaining nut.  "Usually" the labels might be on the side facing you, but I have seen them facing inward on disc grinders (probably the Chinesium mfg.).

[JHCC]

For what it's worth, I don't think it would have made much difference in this case.

[Daswulf]

As Arkie said it isn't dependant on the lable but the disc. "Most" discs I use the lable is up or on flat cutting discs I just put them up but never saw a directional indication otherwise other than style of the disc dictating it. 

Some 3" pneumatic cutting discs have a metal "washer" in the center on one side. Never saw an indication on if that's faced up or down but tend to put it down side. 

[BartW]

In the safety courses at work they explained some european standards about grinding disks. In the 115 mm (4,5 inch) and up grinding disks, they all should have at least a one sided metal washer. And this washer should go against the machine, regardless of on which side the sticker is. This "guideline" is mandatory to get your disks sold in the EU.

For the heavier disks, they should have metal on both sides (but sometimes they are only one sided too) and on one side the rotation direction should be indicated. This is a guideline which isn't mandatory.

So the baseline is; metal washer against the machine. At least so they tell the welders and mechanics :-)

 

greetz; Bart

 

 

[JHCC]

Interesting; thank you.

[pnut]

I can find no manufacturer info on whether the metal ring faces the machine or not. The only thing I could find is that is where the manufacturing date is located.

Pnut

[bubba682]

It looks like the disk says for aluminum in the green if so it would blow up pretty quick in steel so im curious is it an alum zip disk and what were you cutting.

[JHCC]

The disc is for cutting steel; the “aluminum” is from “aluminum oxide”, the kind of grit.

[BartW]

Well; I checked the powerpoint of the safety instructor, and he states the ISO norms : NEN-Iso 525 and NEN-EN 12413+A1. 

[Fowllife]

On a similar not, check the speed rating on the disc's you are using. I learned that lesson about 15 years ago when I bought my hand held gas cut off saw. I grabbed a new 14" blade from somewhere and never though twice. Within the first 3 minutes of using it to cut a house trailer in half the blade exploded, cut a heavy duty fiberglass ladder in half, and then went through the opposite side of the trailer.....stationary abrasive saw blades are rated for a few hundred RPM's less then what a hand held gas saw will spin.....luckily it only cost me a $120 ladder

[JHCC]

Yes, we've touched on that over on my cutoff saw thread.

[evfreek]

What were you cutting, JHCC?  I had an accident with a cutting wheel when I was cutting a piece of steel that was too thick.  It is almost impossible to hold the tool straight in the kerf.  The disk shattered, and a piece struck my finger.  Somehow, it got around the guard.  Fortunately, I had a face shield, safety glasses, leather apron and thick gloves, so it only hurt a lot.  When I was in metal shop, the teacher wouldn't allow students to wear hats or gloves around rotating machinery.  He had a special exception for blacksmiths.  We could wear gloves and/or hats, and I think that you are safer with gloves when doing that risky stuff with the angle grinder.  I don't mean wear gloves around the lathe.  The teacher also allowed the blacksmiths to wear gloves around the machine tools, but I noticed that none of us ever put their gloved hands anywhere the rotating spindles.  We usually kept them in our pockets or behind our backs, and took the gloves off even to touch a switch or handle.

[JHCC]

46 minutes ago, evfreek said:

What were you cutting, JHCC?

2" square tubing. As best I can reconstruct the series of events, the edge caught as I was withdrawing it from one cut, and then the disc bounced and shattered as I started a new cut. I think the first catch may have created a dent in the edge that sabotaged the disc's structural integrity.

[BIGGUNDOCTOR]

I have used small and large discs with chip out of them. I just lean into it at  first and it rounds them up quickly.

If the edge caught, it sounds like there is an alignment issue.