I know there's an expiration date for everything from milk to epoxy resin to discount coupons. But here's a new one on me. I was putting a new cut-off disc on the angle grinder, and in the center is stamped "2021-05 EXP 4/2024". Please educate me why.

 

Just a guess, but the grinding particles are bound together in an adhesive type material which ages like rubber and/or glue and may deteriorate to the point chunks come off of the disc.
Just a guess.

 

R66 is correct. The bonding agents in those wheels have a shelf life for safety reasons.

Ted

 

OMG, enough is enough!

 

Thanks! I never would have thought to look for something like that.

 

When I worked in the steel mill, we had very large hand held angle grinders. Think 12” by 4” wheel powered by 440v. Every evening we removed the wheels and put them in a warming drawer to help keep them stable and intact. Once they past their expiration date they went in the trash. As a test, we let one run at full speed until it let loose. We put it in a steel drum. It destroyed the drum. Believe in the expiration dates!

 

Tomorrow I will check all my various angle grinder discs for dates.

 

News to me, thanks for bringing it up

 

Very helpful topic!!!! I've experienced one disc explosion and didn't know why it happened. I think I do now!

 

Good to know.

Remember to use your PPE, folks!

 

 

In more extreme cases...... you might want to increase your level of protection......

 

I always check and run my cut off wheels to full rpm before using.
Aim the disk so that if it explodes it won't hit anyone.
I have noticed that they will become cracked when laying on the floor.

 

Careful, kid ...

 

This seems like a good place to share a cautionary tale. I was deep into motocross racing in the early 70s and was customizing the frame on one of my bikes. I was using a pneumatic Dremel tool with grinding discs and cutoff wheels. IIRC, my Dremel was an 18,000 rpm model. I had the bike frame on a workbench that had a 4' fluorescent tube fixture overhead. For reasons I don't remember, I had to borrow someone else's Dremel to continue my work and as usual I was wearing high impact safety goggles.

Anyway I chucked up a new grinding disc in the borrowed tool and set about to work on the frame. Suddenly a bulb in the overhead light fixture exploded and fell down where I was working! I stepped back quickly, set down the tool and pulled off my goggles and waited for the dust to settle. After cleaning everything up with a shop vacuum, I still had no explanation as to why the bulb exploded but finally settled on thinking it was loose in the fixture and the vibration caused it to fall and break on the frame.

Once I finished cleaning everything up, I set the frame back on the bench, picked up the Dremel and it was then I noticed the shaft of the grinding disc was bent 90* to the chuck and the disc was missing a portion of it. I now realized that's what caused to bulb to explode! So then I checked the speed rating of the Dremel and found that it was 35,000, well above the max speed for the disc I was using. That was the end of using the borrowed Dremel and so I retrieved mine from whoever I had loaned it to and prepared to start once again.

I picked up my safety goggles from where I had set them down previously, pulled them over my head and only then saw that one lens was shattered! It was intact but shattered. The realization that the fragment of the disc had struck my goggles first before ricocheting into the light fixture was chilling to say the least! The thought of what that would have done to my eye made me an even firmer believer in safety goggles as well as checking speed ratings. And now I'll add checking for expiration dates as well.

 

Good story and a lesson for all. Thanks for sharing!

 

Another good reason not to be using that China crap!

 

Thanks for taking the time to post this. This is the sort of story we need to hear again and again. I know I tend to get complacent about PPE, so beating this into my head is helpful!

 

It happened over 50 years ago so it's not likely the grinding discs were Chinese. The problem was my mistake in using a grinding disc not rated for the speed of the Dremel.

 

I understand. But do you honestly think current China products are any better!