Angle Grinding Discs

I've been trying to figure out how to know when to discard a grinding disc for an angle grinder. I've looked around on the internet, but
can't seem to find an answer to this. I know about the "use by" date, but what's the best way to know when the disc is too worn and should be discarded before it shatters?
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In night school welding class the disks stayed on until they were so small the retaining nut rubbed on the work.
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Your rate of cutting declines as the disk becomes smaller, and this will drive you to put on a new disk before any other consequence is even remotely possible (?)
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Only if you (1) know what you're missing and (2) have another disk.
The condition of their equipment drove me to bring my own, which after all is what I needed to learn to use.
Schools here are funded mainly by local property taxes, and we taxpayers debate, amend and vote on their budget at town meetings, so they have an incentive to appear poverty-stricken. https://participedia.net/en/methods/new-england-town-meetings
Somehow they could find the big bucks to buy decent new equipment, just not the small change for the supplies to support it. I had the same problem as an Army communications repairman and a lab and shop manager at a government research facility. Personal J.C.Whitney mail-orders kept the Army Jeeps running, not necessarily with stock parts. -jsw
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By "smaller" does that mean in diameter or in thickness?
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By diameter.
Obviously, for the same RPM, the peripheral cutting speed declines as the disk gets smaller.
You sort-of move the working angled edge-bevel towards the middle, consuming the disk but also regenerating the cutting medium by exposing new sharp particles.
BTW - for the disk to not wear at all is not a good thing, because it becomes glazed. The particles at the surface become smooth and polished and no longer cut. That can happen on large flat smooth workpiece surfaces. Where the work has that sole characteristic, I have a piece of scrap steel tacked to the edge of the trestle, so can harshly dig the edge of the disk onto sharpish edges, to get new grit exposed.
Rich S
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That makes sense to me.
I'll just worry about inspecting the grinding discs for cracks or other defects and replace them when damaged or the diameter gets too small to work well.
Thanks for the explanation!
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writes:

Though it may not help in your case, this is the test for a cracked grinding wheel: https://www.lni.wa.gov/Safety/Rules/Chapter/807/helpfultools/HT2-PPT.pdf
-jsw
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The disk is reinforced with some type of fibre - glass-fibre? Bursting isn't the first problem, in general. Any damage imbalances the disk and the grinder shakes like mad - completely unusable.
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On 8/28/2018 10:09 AM, Bob wrote: > I've been trying to figure out how to know when to discard a grinding > disc for an angle grinder. I've looked around on the internet, but > can't seem to find an answer to this. I know about the "use by" > date, but what's the best way to know when the disc is too worn and > should be discarded before it shatters? >
I'm cheap. I replace them when it starts taking noticeably longer to grind material away. Usually round 2/3 to 3/4 of the material from the original edges to the swelled hub has been used. I've never had a grinding disc or cutting disc "exploded". I've broken a few cutting discs, and pieces flew off because I was over flexing it, but it didn't "explode." It broke due to mishandling and abuse.
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I shattered a cutoff disk by pushing it too hard on a surface grinder which lacks feel on cutting pressure. It wasn't nearly as dramatic as when an overworked grinding wheel flies apart. -jsw
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