Scary grinder accident

[Cliff Holmes]

Just got a brand-new Jet bench grinder. I turned it on and it started vibrating wildly. Before I could flip the switch back off, the wheel cracked and jammed in the guard, stopping the motor cold. I also heard something go whizzing right by my head, I think a small chunk broke off and came flying out the back chute, bouncing off the wall.

Needless to say, I'll be taking advantage of Amazon's excellent return policy.

[harry strasil]

I learned about grinding wheels from my DAd, we used 14 inch diameter 2 inch wide wheels to grind plow lays, the wheel was put on a broom stick that was clamped in a vise and it was tapped all around the outside lightly and if it didn't ring, it had a flaw and was never put on a machine, I still do that with all sizes of grinding wheels before I mount them. FWIW

[Mitchell Andrus]

All I can say is WOW!

[Brian Kent]

Sorta shows why we should wear those goggles, even when it is "obvious" we don't need them.

[Chris Tsutsui]

Wow so the grinder did a "sawstop" on you, that's pretty amazing...

I'm probably one of the few that wears eye protection AND a respirator when using a grinder when sharpening chisels and that sort.

Don't want ground steel in my eyes or lungs, also the abrasive dust seems to get everywhere because mine doesn't have that dust collection port like that Jet.

[Tom Veatch]

... if it didn't ring, it had a flaw and was never put on a machine, I still do that with all sizes of grinding wheels before I mount them. FWIW

Likewise. One has no way of knowing what the wheel might have suffered on it's way to the grinder. If it has a dull, flat sound, the ONLY proper place for the wheel is in the trash. And never stand in line with the wheel when you turn the grinder on.

[roman fedyk]

Had that happen to me as well. Been using Tormek and Jet slow speed wet grinders most of the time now. When I do use the big grinder I always wear a face shield just in case.

[Tom Slupek]

Like others said ping the wheel around the whole surface first, if it sings put it on if it doesn't put it in the trash.

I have spend fair amount of time in a metal working shops and I have seen a grinding wheel explode on a surface grinder. We were picking up shrapnel from everywhere for about a week. There were chunks missing from a concrete block wall that was at 20 feet away. When they explode they make a lot of damage if you are in the way.

[Phil Thien]

I don't have a grinder, but have thought of purchasing one.

Can I do the "ping" test with the wheel on the machine? Or do I have to remove it?

The reason I ask is, it seems like the test would be worthwhile to repeat from time to time. It would be a pain to have to remove the wheel each time I want to check it.

[Ken Fitzgerald]

Phil,

Hopefully Harry will jump in but...........

He stated that he hung it on a piece of broom stick that was clamped tightly in a vice. I suspect for the wheel to "ring" it has to be able to mechanically oscillate. In short, I think you'd have to remove it and had it suspended freely on something like a piece of broomstick.

[mickey cassiba]

I had the pleasure of running a thread grinder with a 28" knife edged wheel spinning at 2800 RPM. Ringing the bell was part of the morning ritual. A resin wheel blew up once(not on my watch) sliced through the forged wheel guard. Peices wer embedded in an I beam 8' away, the slideways, and the concrete floor under the machine. The operator walked out of the shop(so I heard) and vowed never to mess with rotating tools again. I always ring the bell, even on my little bench grinder. Non ringing wheels do make good door stops, honing stones, and such, but never on the arbor!!!
Mickey

[Brian Muecke]

can someone please elaborate on the technique to see if a wheel is cracked? its not clear to me from the posts above.

thanks.

[Cliff Holmes]

Hey guys, thanks for the advice but I *did* test the wheels beforehand. Pinged and checked for flatness. The problem, I believe, was a bent shaft. It's sure as heck bent now.

[Cliff Holmes]

can someone please elaborate on the technique to see if a wheel is cracked? its not clear to me from the posts above.

Loop a piece of string through the hole and hang the wheel. Then tap it with a hammer. If it's sound, it'll ring. If there's a crack or other defect, it'll make a thud sound. I've heard, though, that this test doesn't work with specialized wheels made for grinding carbide.

[Bob Genovesi]

Hey Cliff, how's your shorts!

[harry strasil]

kinda hard to hang a 14" dia 2" thick wheel on a string unless you are the incredible hulk.

we used different grit wheels for different things, and each time a wheel was put on it was ring tested BEFORE it was mounted on the arbor. And each brand new wheel was mounted and let run for at least 30 minutes with no one near it just to be on the safe side.

[Cliff Holmes]

Hey Cliff, how's your shorts!

Honestly, it happened so fast I never had time to react. Then I just got angry :mad:

[harry strasil]

Also many have said to trash the wheel if it fails to ring, we always sent it back for a replacement, instead of throwing money away. $100 is $100.

[Ken Fitzgerald]

Hey Cliff, how's your shorts!

Bob,

You are getting kind of personal aren't you?:rolleyes:

[kevin loftus]

I use a screwdriver for tapping the wheel. ;)

[Keith Christopher]

Glad you weren't hurt ! I saw a new story where someone grinding teeth on a saw blade had it shatter and drive a hunk of the grindstone into his forehead. He lived but WOW!.

Again, glad you are not hurt.

[Dick Strauss]

I'm really glad you weren't hurt as well!

I'm with Kevin...the plastic or wood handle of a screwdriver will make it ring safely.

(Soapbox)
I'd never let a metal hammer touch my grinding wheels. Have you ever tapped the ~3/4" thick wall of a concrete building block with a hammer and seen it shatter? The same thing might happen with a grinding wheel if struck with a hammer (especially if you catch the corner of the hammer head rather than the flat surface).

Be safe!