Grinding Disc Failures - The Causes?

[Muggins the Mug]

Hi folks,

I apologise if this question has been asked before, but what are the main causes of grinding disc failures?

One of the grinding discs that I got with the Challenger angle grinder has started to break off pieces near the outer rim of the disc. I could hear them hitting the nearby wheelie bin this afternoon. Could it be because they are cheap, me being too heavy handed or using the grinder in the wrong manner?

To be honest, I didn't think I was being that hard on either the disc or the grinder and I know the other OEM disc (which was exactly the same) lasted longer with only a little break up at the edges.

Regards,

Ian.

 

[bawjaws]

i reckon it was the disk muggs, i push pretty hard on mine (to the point of about half of the grinders speed sometimes) and they dont fly apart, but i usually throw them away when the front goes rounded anyway

 

[irondarren]

As far as i am aware grinding discs are glued together. I also believe they are sensitive to storage conditions, ie if they get damp i don't think that does them much good. Best disc i have used are tyrolit ones but you wouldn't want to pay for them lol. I have noticed in the past cheap ones can break up, which makes them dam well dangerous as they flick bits of disk every where

 

[Muggins the Mug]

i reckon it was the disk muggs, i push pretty hard on mine (to the point of about half of the grinders speed sometimes) and they dont fly apart, but i usually throw them away when the front goes rounded anyway

Hi Jaws,

I usually "drag" the disc over the welds that I'm usually grinding (backwards), I take it pushing the disc over the raised welds is the incorrect way of doing it? Some of the welds are quite lumpy due to some of the rods I've recently used.

Regards,

Ian.

 

[irondarren]

i reckon it was the disk muggs, i push pretty hard on mine (to the point of about half of the grinders speed sometimes) and they dont fly apart, but i usually throw them away when the front goes rounded anyway

You mean it slows down to half speed? that is pushing it. lucky my metabo has to speeds flat out and stall, to stall it you have to sit on it it lol

 

[Muggins the Mug]

As far as i am aware grinding discs are glued together. I also believe they are sensitive to storage conditions, ie if they get damp i don't think that does them much good. Best disc i have used are tyrolit ones but you wouldn't want to pay for them lol. I have noticed in the past cheap ones can break up, which makes them dam well dangerous as they flick bits of disk every where

Hi Darren,

After reading some of the horror stories in here and most of all, using common sense - I would never use the grinder without the guard covering me. Thank goodness that the guard was in use and correctly attached, I reckon those pieces of disc flying off at over 11,500 RPM would have left me with some really sore bruises.

Regards,

Ian.

 

[irondarren]

yes they would leave bruises, i know from experience from the 1mm slit disks, if use incorrectly, or shall i say at an awkward angle, where they are prone to sideways pressure, when they blow it dam well hurts your fingers as it bounces off them.

 

[Muggins the Mug]

I've used the 1mm discs a couple of years ago doing a wee job for my father-in-law. I was using a 9 inch and a 4½ inch grinder for taking down some steel and aluminium tubes. They were far better for cutting through quickly than the 3mm discs, but I didn't fancy them failing at any point.

Regards,

Ian.

 

[madkayaker]

once snapped a 9 inch blade cutting up a tower made of box section. The distortion from welding had twisted the box and when i cut it bit the disk and snapped it leavening a chunk behind!

 

[drivewasher]

I used a wheel that had been in damp workshop for ages, It just broke up when applied to the work. I now keep all wheels in a tupperware box and burp it when closing it

 

[Hitch]

As mentioned, storage is an issue. They should be kept as dry as possible, especially if your not going to use them quickly. Something else to check, most discs have a use by date, either on a label, printed on the disc or stamped on the metal centre ring. Check that. Most seem to be about 2 years.

I trust it was a 6mm thick wheel? They shouldnt break up. Sometime you catch the edge, and it will take a chunk out of it, but thats all. Had you worn it down so just the reinforcing was hanging out the edge?

 

[Muggins the Mug]

Hi Hitch,

The disc was well within the "use by date" as can be seen in the photograph below. It's a 6mm disc that came with the grinder, so I've no idea how it was stored before I got it. I only changed the disc a few days ago and had ground down a few rough welds, not really a lot of hard work for it surely.

If I'm being too sore on the disc and working it too hard, then that's something I'd like to correct before something catastrophic happens.

Regards,

Ian.

 

[malcolm]

It won't be helping that you've ground the edge of the disc to a point. Try to keep the edge rounded by varying the angle while grinding.

 

[fluxcored]

Good thread! Picked up some valuable, life saving pointers.

 

[eil]

Pushing very hard is not a good idea thats on any cutting tool come to that its the blade/disc whatever that should do the work, dont overly force it.

 

[Muggins the Mug]

It won't be helping that you've ground the edge of the disc to a point. Try to keep the edge rounded by varying the angle while grinding.

I guess I've just ploughed on with the disc without really understanding how to get the best out of it. I tried to keep within the 15°-30° angle specified, it does look like I've stuck too rigidly to the one angle though.

Pushing very hard is not a good idea thats on any cutting tool come to that its the blade/disc whatever that should do the work, dont overly force it.

I didn't think that I was being that rough on the disc, but I'll back off and take it easier with a brand new disc. Perhaps I was getting a bit cocky with the old one.

Regards,

Ian.

 

[irondarren]

mug the be all and end all of it is they aren't good disks. I have been using the ones BOC sell, and they dont fly apart. It could be because its got a paper disc on it. daft as it may seem, the glue on the label disk will stick to the disk holding bits of the disk to the label, until it breaks off and flies away. Get some better quality discs. believe me not all disks are made equal.

 

[Muggins the Mug]

Hi Darren,

That was my first thought too - crap discs. However it's still a good policy to adopt a "mechanical sympathy" for the tools your working with and not push them too hard, that way if they are bad then your less likely to knacker them or injury yourself. I want to be cautious and treat all tools with respect, just in case I end up with a duffer. I hope that makes sense?

Regards,

Ian.

 

[Normsthename]

Why do all you guys use Hard Grinding Discs?
Are your Welds that bad......
I never use hard discs, I nearly always use a Rubber backing Pad with a P50 sanding Disc.
They are much better for flushing off Welds
With a bit of practice you can flush a weld off smooth ready for priming

Andy

 

[bawjaws]

Why do all you guys use Hard Grinding Discs?
Are your Welds that bad......
I never use hard discs, I nearly always use a Rubber backing Pad with a P50 sanding Disc.
They are much better for flushing off Welds
With a bit of practice you can flush a weld off smooth ready for priming

Andy

i think hes using them to grind the weld right down to the bare metal so he can re use it for welding, not finishing the weld- i think