angle grinder discs: use by dates

Hello,
Whilst tidying the garage, I found some angle grinder discs with "use by" dates on them. They were use by 2012. Does that mean I should bin them? Why do some makes have a use by date and others do not? What happens to the disc after this date: does it become more brittle?
FWIW the ones with the dates were Silverline from toolstation. I had a couple of stone cutting discs that I had forgotten about because I upgraded and used diamond discs but their metal cutting discs also have dates on. The other assorted makes I have seen over the years do not seem to have dates on them but I imagine they are made the same so would be subject to the same aging processes?
Thanks, Stephen.
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Stephen scribbled

I wouldn't try eating them.
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On 18/10/2015 19:32, Stephen wrote:

In industry, they should be binned, but as a home user you can take a chance with them.
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On 18/10/2015 20:15, BobH wrote:

I believe they are more prone to shattering after the use by date. Personally I would use but make sure I had good eye protection as a precaution.
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On 18/10/2015 22:02, ss wrote:

That would be my view too. Apart from resin degradation, there is also the possibility in industry that old disks have suffered mechanical damage by being rattled around in the bottom of a toolbox every day, which is less likely at home.
I'm impressed how much abuse angle grinder blades can take: I think the "toughness" comes from the fibre mat, rather than the resin. Not that I routinely abuse them, but I have never had a failure in more than 40 years and I've never seen one fail during the odd exciting moment. Same is true of the reinforced Dremel disks. (I've destroyed lots of the thin Dremel slitting disks of course).
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Well, I've never heard of this before. I'd have thought it had more to do with where they were stored, ie temp varia tion or humidity which was more of a worry. Brian
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On Sun, 18 Oct 2015 19:32:54 +0100, Stephen

They should all have dates on the metal collar, it was a requirement of the old abrasive wheels act but it's all incorporated in PUWER now.
It's because the resin binder on the thinner (angle grinder type) deteriorates with age.
I'd have to smash and bin them at work.
AJH
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On Sun, 18 Oct 2015 22:01:37 +0100, snipped-for-privacy@loampitsfarm.co.uk wrote:

Thanks for the replies.
These dates were actually printed on the disc rather than the collar, which means that as the disc is used, the date gets worn away!
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On Tue, 20 Oct 2015 11:58:09 +0100, Stephen

I suspect it also means they were made before the requirement to stamp the use by date in the collar so over 10 years old to my knowledge
AJH
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