Exploding Grinding Wheel

I religiously stand to one side when I turn on my bench grinder and I see other people do the same on YouTube. I wonder how dangerous those things actually are, though.

I only heard of one specific case of a grinding wheel exploding and it was pretty horrific. A relative of mine had to rebuild a guys face - which was seriously damaged.

I am always pretty careful about using my wheel and would never hit is or push hard against it but what about the issue of using the side? The drill sharpening jig I bought seems to work only when mounted so as to tough the side of the wheel so what about the 'only on the front ' mantra that you seem to hear pretty regularly.

A higher apparent risk is with angle grinder discs which have various words of warning on them. But, on YouTube again, you see all sorts of antics used by some of the DIY 'performers'.

I never actually had a proper course on grinding and I know they are given to all professional too users. Is the risk real or is it just the fear of litigation that makes managers so careful about grinding? I am at least as careful as the next man (not the one with only one eye).

I have often wondered about drill-grinding jigs too but they seem to exert very little and well-controlled pressure on the wheel, and work with a sweeping action that avoids eroding grooves in it.

Bench/surface grinder wheels are safe enough so long as you take precautions when handling and mounting. Ring test, blotters, dressing etc. If they run out of true or over-speed then you increase the risk of bursting them so always observe the printed rpm limit. standing to one side is good practice but I only do it religiously after mounting a new wheel - just in case I cracked it when clamping.

You're unlikely to overload your bench grinder to the point of stressing the wheel. Your typical 6-8" bench grinder is what 250-330 watts? A surface grinder with a 8" wheel will be 0,75kw - three times as powerful - and they slow down on heavy cuts. You would have stalled the bench grinder by the time the surface grinder had slowed appreciably. Similarly, surface grinders and tool & cutter grinder can grind on the side of the wheel. You can do the same with your bench grinder just go easy - many have spring-loaded rotors. What you don't want to do is dress the wheel too thin or with too great an undercut.

Angle grinder wheels in comparison are very safe. They are reinforced and will take significant damage before they let go. You still need to respect them and they can still harm you if you lose a chunk from jamming or if the centre pops out but the damage is usually more evident before they'll let go and they do so in a much less catastrophic way.

John in a toolroom where I worked many years ago was grinding a 9" diameter shaft between centres when it came adrift and jammed under the grinding wheel. I never saw it happen but being only 15 or so feet away the bang as the wheel shattered was quite impressive. Fortunately Jones & Shipman had anticipated such events and the fully enclosed wheel guard contained all the bits - as did Johns trousers!

Rik

Standing to one side on start up is a good habit. Costs nothing. Takes no extra time. And makes sure that if one in 10 squillion wheels explodes it does not end up in your family jewels.

OMG don't google grinding wheel explosions. The pictures are hideous. I'll never use an angle grinder without a face shield again. And even then with a renewed degree of respect.

Edited By Hopper on 30/06/2020 06:04:46

Edited By Hopper on 30/06/2020 06:06:57

Many years ago I was witness too a wheel going bang, this was a a large wheel on a crankshaft grinder. It was running up and the operator would wait while it settled but this time it just went, 'Bang' and broke into 3 parts. one through the roof and never found and the other two parts clattered across the floor until they came to rest against solid objects, no one hurt but shock all round.

Edited By Clive Hartland on 30/06/2020 07:13:37

Hi Andrew, yes grinding wheels are more prone to bursting during acceleration i.e. during start up, but isn't really a common event, I've never in my working life experienced it happening, but standing to one side until it gets up to speed has been taught in the three abrasive wheel courses that I've had. Light pressure use on the side is deemed to be safe, but not as a continuous process and should be kept as close as possible to the front face. All grinding should be treated with respect and PPE should always be used, even for the shortest of operations.

Regards Nick.

Edited By Nicholas Farr on 30/06/2020 07:44:16

Industrial grinding wheels are particularly dangerous at start up. Whilst standing, the coolant tends to drain to the bottom throwing the wheel out of balance. Once up and running either the wheel has thrown off the coolant or become uniformly loaded.

But until then!

Am always a little wary of my 6" bench grindeer, but have never had any hairy moments, so far, Thank Heaven!

Howard

I'm a stand asider also and I think it is also very important to check ANY wheel before mounting it using 'the ring test'.

If you don't know what that is then Google it.

Brian

I used to grind on a 3 foot diameter, 6 inch wide stone which ran in water. I sat astride it like a motor bike with the wheel turning away from me. The seat was 7 inch thick oak with a steel "robin" bolted across the front and chained to the floor.

I was never nervous using it despite having been told stories of stones bursting.

Apparently french grinders used to grind laying face down to exert more pressure and would have a small dog lay on their feet. If the stone started to run out of true or vibrate the dog would head west this warning the operator to likewise.

We always ran the stone a few minutes with the water tank empty to dry it out at the end of the day. Amazing to hear water shooting off the stone from the portion that had sat in water as the trow was drained.

Another thing to watch for was water freezing in the stone and cracking it so they would be wrapped in frosty weather.

If you do wish to use the side then:-

Dressing the stone at a 10 degree or so oblique ange on the side creates a flat and true area to use whilst avoiding any chance of grooving or thinning the body of the stone.

regards Martin

Not a grinder but 'new starts' at Hinkley Point were always shown the roof of the Magnox turbine hall where the

blades went through.......................

The toolroom where I served my time had a piece of grinding wheel embedded in a rafter. All apprentices where shown this when they did their stint on the grinding section to highlight the danger. We where all sent on the "Abrasive Wheels" course in around 1971. I still have my wheel mounting safety certificate and memories of the dangers from the pictures shown on the course.

A previous employer of mine sent me to do my 1 day abrasive wheel course on 21st June 1979. ....despite me asking for the day off as it was my 21st birthday, I still had to attend...

Both!

People are thoroughly bad at assessing risk. A common mistake is to assume because we personally have never seen something bad happen, it's not worth worrying about. Rubbish!

Been driving half a century and I've never seen a fatal road accident. Despite that 1870 Brits were killed on the road last year. I don't know anyone hospitalised by Covid, but as of today it's bumped off 43,575 UK residents. In both examples our personal risk has been reduced by aggressively managing the causes. Unfortunately, the absence of trouble then causes ignorant opinion to assume there was no problem in the first place. Let's get rid of all those Nanny State road safety measures.

Managers are responsible for the actions of their workforce and get no sympathy from owners, Insurance companies and the Courts when El Thicko causes an accident on the shop floor. Curious thing about El Thicko; frequently heard denouncing H&S in the bar, he becomes completely invisible the instant an incident leaves blood on the floor! These blokes never admit their ignorant macho posturing provoked a mate into taking stupid shortcuts.

Dave

Yes SOD. Spot on. We are unfortunately biologically wired to forget about risk if we are not seeing the results regularly. Otherwise our ancestors would have never left their cave for fear of sabre tooth tigers etc.

But i think the stand to one side practice pre-dates our modern lawsuit culture by many decades, based on shop floor experince like those described above.

@SOD Good comments about perceived risk. Problem is that people just do not understand statistics - why else would Lotteries make money? It was good to read all the above posts; I guess the topic needed an airing.

I realise that my noddy 150mm bench grinder is a lot lower risk than massive, highly stressed wheels but, as has been said, it's no hardship to do a quick 'genuflect' when I turn it on. At this level, in the market, quality control and pricing will not be too much of an issue so I am probably on reasonably safe ground and the horror stories seem always to involve idiots and big machines (as with most things male).

I am particularly conscious of the wheel at the mo because I replaced the 'fine' grey wheel that came with the grinder 25 years ago with a white 'sugar wheel'. Such good value!!! It quietly shifts HSS quickly enough for me to get proper looking faces on cutting tools and it also took no time at all to re-do my wood plane and a chisel without overheating.

Dressing it was very satisfying and there is less vibration than with the old wheel, ever. I'm making a better rest for it which will improve things even more.

Money well spent.

Hi Andrew, please don't get complacent about the size of your wheels, as the smaller diameter of the wheel, generally will spin faster than a larger one. As it is the peripheral speed that counts, bits flying from it will be very much at the same speed, it's just the mass that will probably be significantly different.

Regards Nick.

Edited By Nicholas Farr on 30/06/2020 10:37:10

Has it really bumped off that many, or does that number include those that died with Corona virus rather than of it, or Corona related, or Corona suspected, or any other thing that is designed to make you think it's a Covid-19 death?

El Thicko could also be seen as those that are taken in by what they see on TV and read in the press and aren't interested in alternative views and opinions.

Sexist Comment: "These blokes never admit their ignorant macho posturing provoked a mate into taking stupid shortcuts".

Martin.