Lawnmowerboy
Member
- Messages
- 2,165
Hi all, been asked to do an abraisive wheels course in 3 weeks time, has anyone else here done one? And know what to expect?
will
will
- Thread starter Lawnmowerboy
- Start date
pedrobedro
Man at Matalan
- Messages
- 13,119
- Location
- CX near Chesterfield
I did one many years ago when fettling and they showed us how to change and dress a wheel and how to change grinder discs plus how not to do anything silly really.
gordon stephenson
Member
- Messages
- 7,473
- Location
- Skelton in Cleveland U.K.
As above, All common sense stuff, Make sure that the wheel RPM is higher than the machine, That the wheel is a good fit on the spindle. give the wheel a little tap and listen for a ringing sound not a dull thud denoting a cracked grind stone, How to correctly store spare stones. they usually explain the difference between grind stone types, All simple precautions to be taken, All our 7" and 9" windy angle grinders had a registration number engraved on the body and the discs had a serial number engraved on the centre aluminium collar, All disc changes had to be logged, what number disc had been fitted to which machine and by who,
I did the course many years ago, I wasn't allowed to change a grinding wheel until I'd been.
Course could have been covered in a few hours, rather than a whole day - get lots of sleep the night before and drink plenty of coffee.
People in work, who have recently attended, have the same opinion
............. Enjoy
Course could have been covered in a few hours, rather than a whole day - get lots of sleep the night before and drink plenty of coffee.
People in work, who have recently attended, have the same opinion
............. Enjoy
chevy2
Member
- Messages
- 1,631
- Location
- Herts.
Done this course a couple of times,
the one good thing most dont realise is dont fit a larger worn grinder disc onto a smaller grinder,
I,e when your 7" disc is down to 4.5" diameter dont fit it on the 4.5" grinder as it runs faster than the 7" so with it comes the risk of disc explosion.
the one good thing most dont realise is dont fit a larger worn grinder disc onto a smaller grinder,
I,e when your 7" disc is down to 4.5" diameter dont fit it on the 4.5" grinder as it runs faster than the 7" so with it comes the risk of disc explosion.
Engineer1964
Member
- Messages
- 1,055
pedrobedro
Man at Matalan
- Messages
- 13,119
- Location
- CX near Chesterfield
Not to mention that the centre hole will be different also
Everything I have seen over 100mm with a 16mm bore has the same centre till you get up to Stihl saw and 355mm chop saw size. 115, 125, 150 and 230mm all have 22mm centres.
As Pedro 4.5" through 9" all use the same size centre bore, being pedantic it's 22.23mm (7/8").
All of them typically have a max surface/circumferential speed of 80m/s which obviously doesn't take diameter into account. For a new 115mm disc that equates to ~ 13000rpm, for a 180mm ~ 8500rpm and for a 230mm disc ~6500rpm. While the rpm of the machine stays the same as the disc wears the surface speed drops...
Will, some of it will be boring, none of it will be challenging to anyone that's capable of outwitting a corpse and you will learn something
All of them typically have a max surface/circumferential speed of 80m/s which obviously doesn't take diameter into account. For a new 115mm disc that equates to ~ 13000rpm, for a 180mm ~ 8500rpm and for a 230mm disc ~6500rpm. While the rpm of the machine stays the same as the disc wears the surface speed drops...
Will, some of it will be boring, none of it will be challenging to anyone that's capable of outwitting a corpse and you will learn something
KemppiFrog
Member
- Messages
- 4,298
- Location
- Aquitaine
Sorry, this is rollax. On the smaller grinder the rim speed is under the limit, as alluded to in other posts. It is all about centrifugal force, and that is dependant on the diameter and RPM.
If the courses tell you not to use reduced big discs on smaller, higher RPM machines, then they are being influenced by H S&E, not by basic physics.
If the disc is within the diam of the smaller machine, then fine.
KF
madkayaker
Pro sparkey Pro Welder
- Messages
- 13,678
Ok so you use a 9inch grinding disk till its small enough to fit into a 4.5inch grinder. Working away and the disk shatters. There is an investigation and fault is pointed in your direction due to the above. I wonder what your employer and there insurance company will say?
chevy2
Member
- Messages
- 1,631
- Location
- Herts.
Take a read of this regarding grinding discs being run faster than their designed speed....
http://www.mmsonline.com/articles/grinding-wheel-safety-respect-the-maximum-speed
Last edited:
Lawnmowerboy
Member
- Messages
- 2,165
But it's sureely not all about h&se, It's the same reason they reccomend do not reuse bottle on a bottle of water, sales&profit? Is it not about the meters per second that the wheel travels and as it wears its circumference reduces so can be spun faster to compensate for this? I was told by the last person who did the A/W course at my workplace he was told that any rotating blade and abraisive wheel has massive safety parameters, much like the SWL of straps and car jacks. To allow for numpties to be numpties.
penfold
Ambassador plenipotentiary
- Messages
- 2,116
- Location
- Argyll and Bute, God's own country.
Mine was a yawnathon DVD followed by a bit of practical instruction in how to store, fit and dress wheels, inspect for cracks etc. I imagine most are like that, coffee and a good night's sleep is good advice.
KemppiFrog
Member
- Messages
- 4,298
- Location
- Aquitaine
That wont load, but I suspect is about running them too fast when they are full size
chevy2
Member
- Messages
- 1,631
- Location
- Herts.
Sorry it wouldn't load for me either,
Here it is again.
http://www.mmsonline.com/articles/grinding-wheel-safety-respect-the-maximum-speed
KemppiFrog
Member
- Messages
- 4,298
- Location
- Aquitaine
Thanks, works now.
And it was about overspeeds on given diameters.
If one doesn't exceed the rim speed, then it is OK.
From the engineers handbook: It is about flywheels, but still applies.
'The centrifugal tension, which tends to rupture the rim, depends soley on the rim velocity and is independent of the rim radius.'
KF
And it was about overspeeds on given diameters.
If one doesn't exceed the rim speed, then it is OK.
From the engineers handbook: It is about flywheels, but still applies.
'The centrifugal tension, which tends to rupture the rim, depends soley on the rim velocity and is independent of the rim radius.'
KF
