- Thread starter scotto75
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pedrobedro
Man at Matalan
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They are usually tested to break at about double the running speed so theoretically you won't have issues. But I wouldn't run something not designed for purpose, and I dare say any professionals insurance would probably be voided should the worst happen. But it's all how comfortable you feel using them I suppose. Plus I don't pay for them, work does.
rtbcomp
Moderator
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It's the linear velocity at the edge that's important, so as the disk wears down the speed at the circumference decreases for a given rpm, so it's safe to use in a 4.5" grinder at a higher rpm when it's worn down enough to fit.
As for the OP's original question, some discs have a 'use-by' date on them. If it has chunks missing from the edge or is cracked then throw it away. Break it in half so nobody is tempted to pick it out of the bin and use it.
As for the OP's original question, some discs have a 'use-by' date on them. If it has chunks missing from the edge or is cracked then throw it away. Break it in half so nobody is tempted to pick it out of the bin and use it.
Some years ago i was cutting some engine beds out of a GRP yacht using a 4.5" grinder & stone cutting discs, my grinder expired so i borrowed a friends one, it was a dreadful italian thing & he habitually used 4.5" discs on it, The grinder ran fast at 12,000 rpm & guess what the discs were rated at 10,000, one blew on me as i was cutting looking down at the edge of the disc. I was wearing a racal airstream powered respirator with polycarbonate face visor & a big shard/s of the blown disc broke the visor. That day the Airstream helmet paid for itself & i think if i had not been wearing it i may have had a white stick today.
Another bloke down the boatyard was cutting scupper holes out with a 9" grinder on a ferro boat, he was using the wrong discs & one burst. A third of the disc slid between his ribs under his arm & punctured his lung. He was lucky to survive.
I rest my case!
Another bloke down the boatyard was cutting scupper holes out with a 9" grinder on a ferro boat, he was using the wrong discs & one burst. A third of the disc slid between his ribs under his arm & punctured his lung. He was lucky to survive.
I rest my case!
brightspark
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and presumably the guard wasnt fitted because if was it wouldnt have disintegrated in his face just spat it forward and out. been there done it and got the teeshirt and a few scars 
evobilly666
Member
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On a recent health and safety day at a quarry, the HSE guy talking about abrasive wheels recommended against full face shields. A recent incident involving a full face shield (as I also wear) and a burst cutting disc. The disc went up under the chin of the shield and bounced around on his face until it stopped spinning. Goggles wouldn't have held the disc in there and the initial impact would likely have been the only injury.
Food for thought although i think i will continue to take the risk due to the extra protection they offer in other areas.
Food for thought although i think i will continue to take the risk due to the extra protection they offer in other areas.
