Angle grinder cutting disks - cranked or flat?

[RicksAlfas]

Why are some angle grinder cutting disks cranked, and some flat?
I’m talking about small 115mm diameter ones for cutting metal.
What’s the advantage of one over the other please?

[colin_p]

From my experience;

Grinding wheels are offset / dished.

Cutting wheels are flat.



And whilst we are on the subject, a "Health and Safety" moment, especially for DIY'ers who may not know;

When you mount a new disc, run it for a full 30 seconds (no load) holding it away from you and above something soft (bucket of sand or an old coat etc). Reason being; if a disc was to fail, and they do, chances are it'd happen in that time. You don't want a newly fitted disc to explode into your face soon after you switch the grinder on. Even better, do the 30 second test and use full face protection rather than just goggles.

[guindilias]

Cranked are generally stronger, and give you a better view of what you're cutting.
Flat cut more accurately and keep more sparky bits of metal in the guard, rather than all over your face (hopefully not eyes - either get goggles, or cut blind - I had to have a tiny speck of metal sucked out of my eye with a hospital electromagnet a couple of years ago, it had started to rust - you do get a free rust tattoo on your eyeball, though! And yep, hospitals have magnets just for that purpose - looks like a big hairdryer.
And if you are using cheap blades, stick to straight ones - that way if it fractures, you are less likely to get blinded or worse..

[guindilias]

colin_p said:

And whilst we are on the subject, a "Health and Safety" moment, especially for DIY'ers who may not know;

When you mount a new disc, run it for a full 30 seconds (no load) holding it away from you and above something soft (bucket of sand or an old coat etc). Reason being; if a disc was to fail, and they do, chances are it'd happen in that time. You don't want a newly fitted disc to explode into your face soon after you switch the grinder on. Even better, do the 30 second test and use full face protection rather than just goggles.

I had 2 in a row fail on me out of a box of 100 cheapo Chinese ones - binned the lot.
Also, if you drop a disc before you fit it, chuck it away. I know they can cut though metal, but if there is a tiny fracture in one - it is going to come apart before you have finished using it.

[colin_p]

guindilias said:

colin_p said:

And whilst we are on the subject, a "Health and Safety" moment, especially for DIY'ers who may not know;

When you mount a new disc, run it for a full 30 seconds (no load) holding it away from you and above something soft (bucket of sand or an old coat etc). Reason being; if a disc was to fail, and they do, chances are it'd happen in that time. You don't want a newly fitted disc to explode into your face soon after you switch the grinder on. Even better, do the 30 second test and use full face protection rather than just goggles.

I had 2 in a row fail on me out of a box of 100 cheapo Chinese ones - binned the lot.
Also, if you drop a disc before you fit it, chuck it away. I know they can cut though metal, but if there is a tiny fracture in one - it is going to come apart before you have finished using it.

Similar experiences then.

I've had a lump of metal off the grinder in the eye twice in my lifetime. Both times wearing goggles as well as I couldn't wear the full face visor underneath the car. I reckon the bits got in through the side vents of the goggs.

My eyeball metal removal experiences differs though, they dug them out with a needle! Didn't get the eyeball tatoo though!


Back to grinders generally - they are dangerous, very dangerous.

[Andrew_S]

I bought a pack of these this morning and they seem o.k.

https://www.screwfix.com/p/norton-cutting-disc-4-1...

[guindilias]

Worst injury I've ever had from a grinder was when I was wearing a woolly jumper, and one of the threads got caught in a wire brush attachment I was using. Pulled the jumper all the way up from my stomach to my chest, and almost hit my neck.
Nice wire-wheeled scar right up my front, and that was about 15 years ago!
Now it's not really visible because I have more body hair than any man should be blessed with - but bloody hell, it hurt!

Now I only use power tools if I'm naked and shaved all over, with a jockstrap to protect the essentials and goggles.

Some of the neighbours have complained about me cutting things like this in the front garden, but I just give them a lecture about the HSE, and they quickly become bored and go back inside.

Then the police turn up, and give you a lovely warm bed for the night - though it's a pretty thin mattress. And the in-house catering is rubbish.

[dhutch]

colin_p said:

From my experience;
Grinding wheels are offset / dished.
Cutting wheels are flat.

This.

I've used Smith& Arrow via their eBay store of late, no complaints.

http://www.ebaystores.com.au/smithandarrow

Daniel

[colin_p]

guindilias said:

Worst injury I've ever had from a grinder was when I was wearing a woolly jumper, and one of the threads got caught in a wire brush attachment I was using. Pulled the jumper all the way up from my stomach to my chest, and almost hit my neck.
Nice wire-wheeled scar right up my front, and that was about 15 years ago!
Now it's not really visible because I have more body hair than any man should be blessed with - but bloody hell, it hurt!

Now I only use power tools if I'm naked and shaved all over, with a jockstrap to protect the essentials and goggles.

Some of the neighbours have complained about me cutting things like this in the front garden, but I just give them a lecture about the HSE, and they quickly become bored and go back inside.

Then the police turn up, and give you a lovely warm bed for the night - though it's a pretty thin mattress. And the in-house catering is rubbish.

Reminds me of arc welding in rigger boots. Never weld in rigger boots.

Carpet slippers only for me now for welding.

[V8RX7]

I've never heard of a cranked / angled disc and a quick google doesn't come up with anything either

I always use the 1mm thick discs that used to be called slitting discs.

Never had an issue with them breaking but I'm fairly careful and generally wear a visor

I have skinned my inner left arm after cleaning a cylinder with a wire brush attachment that then ran down my arm and buried itself in my thin gloves - annoyingly I knew it was a stupid idea the the time but I CBA to walk to the vice.

[Dave.]

colin_p said:

Back to grinders generally - they are dangerous, very dangerous.

This!

They scare the st out of me, I fking hate them!

Used one once in college, directly after being showed a video of when things go wrong.

Only used one once since, to remove two rear droplinks when all else failed.

Even more stupidly, did it wearing just my glasses for protection, luckily I didn't get anything in my eyes, but I did ruin my glasses!

[Kinkell]

Always goggle up and wear decent gloves. I was using one handed flapping lacquer off a wheel in my other hand when it grabbed the glove and deskinned my palm. Handle with extreme care always.

[guindilias]

It's a bit like running a chainsaw without a chain brake - except that you can turn off the saw and put it down, it's not a hazard anymore.
Grinders keep spinning for bloody ages though, and like to "walk" towards you if you turn then off and put them down - especially if you have long hair, and are working lying down under a car.
I am convinced they are attracted to me...

[Kinkell]

I only recently realised that you can flip them on their back and rest them on 2 little nipples instead of it scurrying across the garage floor entangled in the much repaired cable.

[wolfracesonic]

colin_p said:

From my experience;

Grinding wheels are offset / dished.

Cutting wheels are flat.

This but I'm not sure why, I don't think it's a visibility thing as mentioned; possibly so you can identify them easily once all the labels are worn off, I know you're not supposed to use cutting discs for grinding

[Skyedriver]

Nicked a finger yesterday cutting a tile. Strange one as the stone disc was struggling but an old, worn disc in the tile cutter machine went through the tile like butter.
Had the occasional run in with wire wheels, usually in a drill though.

[allegro]

Really is one of those occasions where investing in the best quality you can afford if the correct option, cheapo discs can be lethal!
Also be warry of buying from car boots etc.
Discs have a sell by date for a reason!

[RicksAlfas]

Thanks for the replies everyone. I think the butt naked except for a jockstrap and full face protection is the way forward.

These are the ones I was looking at. Like others have posted I've only seen flat cutting disks and cranked grinding disks before, but these are Bosch cutting disks in either format:

Flat:
https://www.amazon.co.uk/dp/B007PB1GSC/?coliid=IVH...

Cranked:
https://www.amazon.co.uk/dp/B009RQ39C4/?coliid=I1Y...

[Megaflow]

Dave. said:

colin_p said:

Back to grinders generally - they are dangerous, very dangerous.

This!

They scare the st out of me, I fking hate them!

Used one once in college, directly after being showed a video of when things go wrong.

Only used one once since, to remove two rear droplinks when all else failed.

Even more stupidly, did it wearing just my glasses for protection, luckily I didn't get anything in my eyes, but I did ruin my glasses!

I have now problems with 4.5” grinders, but the 9” ones are terrifying! I’d rather use a petrol disc cutter than a 9”, petrol ones have a clutch and don’t kick back.

[anonymous-user]

And don't forget ear protection as well.