When grinding discs go bad?

[gaz1]

I've seen lots of grinding discs and wheels and I've seen a few fail.

I have never seen one fail all by itself, no matter how old, in use - every single failure has been due to the operator - wrong material/letting the disc get pinched/twisting the disc during a cut/using a damaged disc ("it'll wear down straight")/incorrect mounting, etc. I've even seen discs run past their rated speed with no issues at all (although it's not something I would do personally).

Grinding machines are inherantly 'safe', but are imo the machine most often used in an unsafe manner...

ive done a few things i shouldnt ive pinched the disc in the thin ones and its seperated from the wheel but when ive been shaping something with the thin disk usualy when cutting circles out with guard on

ive damaged a grinding disk and thought it will straighten on its own it did far worse i will admit as it vibrated like hell and it did shatter off some pieces in end id had enough binned the disk and all that while no guard on it

ive taken guard off yet again and using it for a 5" flap disk

i should really make a guard for it which i probably will do or might just get a new 5" grinding disk it seams to be the one i use the most more than the 4 1/2" one

both the 9" and the 4 1/2" have had me the 9" pulled into ground and stalled and blew fuse the smaller one i caught on grinding wheel i still use the smaller one with one hand often while doing another thing with other its how it caught me the first time

but to mention something else ive had a diamond stone cutting wheel on steel often so really i should know better

 

[Maker]

the actual maths is phd stuff

By that logic, I'm a doctor.

The maths is very simple

Force = Mass x Acceleration,
Centripetal Acceleration = (Surface speed^2) / Radius
Surface speed = Pi x 2 x Radius x Revolutions per second
Revolutions per second = RPM/60

All very simple, well known equations, which can be substituted into each other like:

So Force = Mass x ((Pi x 2 x radius x (RPM/60))^2) / Radius

(Use SI units)

Having said that, an online calculator is faster.

 

[Pete.]

Those equations calculating the force of a given mass at a given radius don't work for calculating the forces in a spinning solid disc.

 

[Maker]

I tested it before I posted and got the same answer as your calculators.

 

[weldequip]

Jesus H! You've all got far too much time on your hands. Just buy a quality disc, wear eye protection and get the job done (instead of talking about it!).

 

[Pete.]

I tested it before I posted and got the same answer as your calculators.

Ok, but the calculator I used doesn't work it out for a disc either hence my original comment. It was intended as an indicative example.

 

[brightspark]

christ ive been doing it for 44 years without incident and im still here no wonder nothing gets done nowdays

 

[brightspark]

You must have died at least 6 times so far from doing that - didn't mention that did you, you naughty thing

yup marvel0us what the medics can do nowadays