Grinding wheel ..balancing hole?

I bought a grren grit grinding wheel for a small grinder I had

after mounting it the blotter flapped out slightly showing a hole

is this ok? looks cast in

I've never seen a hole before on a stone

Its about 6mm deep perhaps 7-8mm dia

To balance a wheel you dress it on the periphery using a star wheel dresser, a diamond stone, or in some cases another abrasive stick, From the close up it doesn't look like a cast in hole to me it's more like some sort of impingement on the side of the wheel, in which case the bonding has been damaged, I wouldn't trust it. Give it the 'ring test' I'll lay odds on it gives off a dull, dead sound, bin it! . In all my years in the engineering business, working & teaching, I've never come across this before... I could be wrong but...

George

p.s. on some wheels the steel side washers may have slots in where there is the facility to add counterweights to balance the wheel on the shaft on a set of balance wheels ...I still don't like the look of it.

George.

I've contacted the supplier they asked for the pictures so we will see what they say

May just be the lighting, but I don't like the look of the 'cracks' starting from the hole (especially obvious in top picture).

A ring test is good for revealing an unseen flaw in a grinding wheel but in this case it is not needed. With a visible manufacturing flaw like yours the wheel should not be used anyway.

I have seen two large wheels explode during my time in the industry - both of which were caused by "stackups" rather than faulty wheels and the power released is scary.

Don't take a chance - scrap that wheel before it scraps you.

Rik

Edited By Rik Shaw on 22/03/2016 18:19:40

Ian, please heed the advice above and don't be tempted to try and use it, get a replacement.

Grinding wheels can be lethal if they give way.

I agree with that, I am sure I can see the crack as well.

Above all, be glad you didn't try and use the wheel.

Well spotted David.

Neil

Crack it in half so no one ever mistakes it for being safe and mounts it on a grinder. Then maybe keep the pieces to use as handstones?

Right

I pulled it off to investigate more and its definitely not cracked it rings as a stone should

But theres another hole on the other side

these are nice clearly made holes 8mm dia perfectly round and flat bottomed 5mm deep

ones at 12 o clock and the others at 4 o clock on the other side

these are put in during manufacture

its a 125mm 13mm wide wheel and they are 32mm and 35 from the centre

Ian, from the look of that photo, there is NO WAY in this world that I would spin that wheel up, let alone stand in front of it and grind something. It could conceivably be an unfortunate visual effect, but for the sake of a couple of quid I wouldn't risk it. Plain and simple!

Even at the best of times I treat wheels like a faulty gun cartridge that failed to fire.

Roger

Hi Ian

Well done for spotting that, and for bringing it to light. It was lucky you were paying attention and noticed the label flapping out. Wow.

Would it be possible to let us know the wheel manufacturer (though it looks unbranded to me)? And, can you tell us the manufacturuers code on the label? Best not mention the supplier as that would be unfair I think (unless it was a no name ebay seller).

I did read that the resin bonded type of wheels have a 2 year shelf life. Mind you, I don't think any shelf life deterioration has caused those holes, else the bits would still be there under the label.

Thanks

Steve

Some more photos and a blu tack impression of the holes

And the label which if its not clear is

1 125x13x31.75z 331556/ indistinct

C60 J6U

40 m/s mos-6110

Supplier was chronus so hopefully they will respond to my email pictures today

Just had this in from Chronos

Might be worth having a look at this video by Don Bailey
from Suburban tool in USA.

"How to dress and balance a surface grinding wheel"
In this 13 minute video the principle points of interest
are at 9 min 31 seconds and 10 min 34 sec .

There are many more interesting videos from Suburban
tool that are worth watching for people interested in grinding.

John

I think we're all waiting on what response you get with great interest.

FWIW...

Looking at the marking quoted & the universal standard marking system... Abrasive, Grain, Grade, Structure & Bond...

C60 J6U denotes ... n.b. The 'U' in your pic is a digital 'V'

C = Abrasive - Carbide

60 = Grain - Medium

J = Grade - medium

6 = Structure - Regular

V = Bond - Vitrified ( resinoid )

Carbide is generally Dark green, light green, sometimes black, your example shows a 'Grey' wheel, to me this denotes an Aluminium Oxide abrasive... Identifiable by 'A' not 'C', so for me, nothing ties in with the 'norm' ... as you say it 'rings', in essence I still have big doubts & am still of the opinion to recommend that you dispose / discard it.

George.

Hi all.

I havn't a clue about how grinding wheels are made but presume it is some kind of moulding process. In which case could it be that the little holes are being made by ejector pins that have not retracted completely during the moulding (similar to plastics injection moulding process)

Kind regards

Anna

I recommend every one mounting and using abrasive wheels of all kinds to get a copy of HSE publication "Safety in the use of Abrasive Wheels " HSG17

It can be downloaded free from the HSE web site. It contains all you need to know about the correct selection, use and mounting of all types of abrasive wheel and is most certainly not a "nanny knows best" publication.

I spent 50 years in tool making and used thousands of grinding wheels. I never saw one with holes in like that. I would bin it and get another.