Angle grinders...

[NP99]

I have a 4,5 and 9 in angle grinders and recently had trouble using the 4in doing some cutting jobs. The discs shattered and broke pretty easy. The job was just cutting some aluminium posts.

After researching the web and reading about some of my bad habits which I wasn't aware of, I thought this the place to ask of those in the trade.

What disc for what job and how to apply disc size and wattage of the grinder to a particular job.

Also read that the 9in grinders have been banned on worksites!

[megatexture]

I use my 9" heaps and demo saw a fair bit and never heard anything like that yet ?

[TPC]

All building and mine sites in SA have banned 9 inch grinders.

[megatexture]

Next they will try and make you keep guards on them!

[NP99]

The 9inch is a monster of a tool. I can see why they have been banned.

[Clunk]

From my understanding and from what I've been told, when ally is cut and heats up it can clog the normal cutting discs (mild steel) which can cause them the catch on what your cutting and then shatter. I've been told if you rub plenty of surfboard wax on the discs it will help prevent clogging but you have to keep the disc waxed up. I've been told cutting discs for Ally are not for the faint hearted either and it's probably best to use a saw............

Not my opinion but just passing on what I've been told by someone in the know.

[jack]

Aluminium is fairly difficult to cut with an angle grinder.
I recently purchased some checker plate and had it cut close to size with a guillotine but knew it needed some more minor cutting when I got home. I discussed this with the fabricators and they told me to use the thinnest blade possible and to lubricate the blade to keep it cool. They used pig fat on thier angle grinder. Because Aluminium is such a soft metal it melts into the blade, try using a bench grinder and see how quickly it blocks the stone wheel.

Also 9" grinders are banned at all BHP sites and I think all WA mining sites as well.

Edit: just saw Clunks post

[TPC]

I was told when I did my apprenticeship a few decades ago that aluminium does not go near grinders or linishers, the guys in the metal shop would string you up if you tried.

[NP99]

After doing it........can't agree more!

[Ben-e-boy]

1mm turbo wheels, a grinders best friend.

Most sites I have been on ban 9in grinders BUT.... You can use a 7in grinder which has the same size motor but smaller disk. :D

[BigRAWesty]

1mm turbo wheels, a grinders best friend.

Most sites I have been on ban 9in grinders BUT.... You can use a 7in grinder which has the same size motor but smaller disk. :D

It's a joke hay..

My favorite 2 tools in my shed..
The 5" is my file and the 9" is my grinder..
As mentioned alloy melts into the disk pores, so grab a 1.6mm inox free disc. This is a finer disc with a good reinforcement layer. I use 1mm disc but you have to be steady. To much side load and boom..
Don't stick it all the way in!!! Contrary to belief a little is better. :D
Only have the disc just cutting the bottom of the plate, the less disc in the alloy, the more fresh disc you have..
Use a handle, you get more control.
Do short stints, alloy the alloy to cool to avoid excessive build up on the disc.
And goes without saying, correct ppe.

[NP99]

Good words mate, if I knew last month....:)

[threedogs]

Would use those metal diamond wheels for alloy , my mate rips into me if I dress a piece[small] aluminium on the 8" grinder..
He says the wheel will explode. I have taken that advice on board. I have 4",5" and 9" grinders
The 5" I use with the cutting disc on and the 4" has a flap disc. mainly for cost. very rarely use the 9".
Years ago on a Job site a mate was told to grind a piece of steel that was freshly oxy cut. After cooling it he knelt on it and used the 9' with no guard
needless to say it grabbed and cut very deep across the top of his knee, no blood could see the bone he cut through. and he never returned to work

[kevin07]

From my understanding and from what I've been told, when ally is cut and heats up it can clog the normal cutting discs (mild steel) which can cause them the catch on what your cutting and then shatter. I've been told if you rub plenty of surfboard wax on the discs it will help prevent clogging but you have to keep the disc waxed up. I've been told cutting discs for Ally are not for the faint hearted either and it's probably best to use a saw............

Not my opinion but just passing on what I've been told by someone in the know.
yes clunk you are correct the aluminium will clog a standard cutting grinding disc by way of melting and getting caught inbetween and boom can occur one of the first things I was told in the hire industry the way to get around this is with a green disc specific for ally.kev

[MudRunnerTD]

We cut allot of tube and use a drop saw with a blade with a high tooth count. 80teeth. Works a treat.

Most shop fitters doing partition work will use a drop saw for their cutting on site. ( well did back in my day, been offsite for a long time though)

For cutting sheet like checker plate I would have no hesitation pulling out my 9" Makita power saw with a fine tooth blade. The trick though is to set the blade depth to only a little more than the cutting depth required so the face of the tooth is hitting the stock at a broad angle as far from 90d as possible. A 90d cut will cause some deformation in the sheet as the tooth is smashed through.

I have used my 6-1/2 Makita 18v to cut ally a couple of times and also used my scroll saw to cut square slots in a 5mm thick sheet of aluminium switch panel when building my GQ. Worked a treat. Lots of teeth, ally is soft.

[Winnie]

If I want to cut ally I go to my mates place and use his old man's milling machine =]

[threedogs]

Please explain,
but a 9" grinder is not a tool for a first time user, geees even turning them on can be a chore.
I stand on them to start just in case on/off is iffy. Can see why they are banned though.

[MudRunnerTD]

Please explain,
but a 9" grinder is not a tool for a first time user, geees even turning them on can be a chore.
I stand on them to start just in case on/off is iffy. Can see why they are banned though.

Hi John,

Wha did you need explaining?

When using a 9" angle grinder I am a big fan of being in the standing position with both hands on the machine in the operation grip, elbows in and braced to you body, one foot slightly forward like you are ready for a fight. Good balance, a firm grip and respect for the unit will see the job done safely.

As I See it the problem with standing on the unit is when your trying to the lift the bloody thing into an operating positionwhile it's spinning. Nasty bit of kit.

I remember sitting at the Christmas table about 10 years ago while my then 15 year old nephew told me how he and his mate were doing a heap of work on cars and his mates dad let them use his 9" angle grinder in-supervised and how his mates Dad had removed the guard cause it was in the way! I hit the farking roof at the Christmas table!!

He is my nephew by marriage and my wife is the youngest of 4 girls and this young fella did not have a dad so no male figure. I am that guy now. My sister inlaw's all just looked at me. No idea. Needless to say he never used the grinder again. His friends Dad should be bloody shot!! D1ckhead! Right there!

[threedogs]

Nah trying to figure out how a milling machine can cut alloy sheet or alloy.
Agree with what you're saying, brace yourself
Need the guard on regardless if it cant cut deep enough.
You cant take short cuts as you said its a bit of Kit

[growler2058]

Angle grinders are my pet hate in construction as far as getting blokes to do the right thing when they use the things. Use 2 hands all handles and guards attached don't cut above your head, use a visor. We had a kid get a battery 4" kick on him and smacked him in the mouth, not a pretty sight. Plenty of people tell me that battery A/G doesn't kick back I reply bullshit then show them the photo.

[Clunk]

That reminds me, I must get a visor....... got goggles and glasses but will be no good if me grinder kicks

[Parksy]

A clogged disk equals an uneven disk and when spinning at very high rpm equals boom. Should always inspect the disk. If some clown before you has clogged it for the next person, chuck it.

[growler2058]

Caught a cock head on site (lucky for him) had a cut quick blade (14") worn down and was attempting to put it in a 7". Quick cut blades are rated for 4400rpm 7" grinder 8600rpm. No visor nadda it would have blown apart at 8600 rpm would have been nasty.


Have a google of Angle grinder injuries PHARKN NASTY!!

[threedogs]

Heres a ripper for you true story, Italian guy up the airport doing home renos and was cutting in some door architraves.
Saw wouldn't fit so he removed the saw blade and fitted it to the 9" grinder. Turned it on and lined it up for a cut ,,,,,,,,,,,,,,,
as soon as it touched the timber it bit took off and ended up embedded in his shoulder blade, nasty as you say.
He went to Emergency with saw in his back, very lucky person an idiot but lucky.

[NP99]

Hi John,

Wha did you need explaining?

When using a 9" angle grinder I am a big fan of being in the standing position with both hands on the machine in the operation grip, elbows in and braced to you body, one foot slightly forward like you are ready for a fight. Good balance, a firm grip and respect for the unit will see the job done safely.

As I See it the problem with standing on the unit is when your trying to the lift the bloody thing into an operating positionwhile it's spinning. Nasty bit of kit.

I remember sitting at the Christmas table about 10 years ago while my then 15 year old nephew told me how he and his mate were doing a heap of work on cars and his mates dad let them use his 9" angle grinder in-supervised and how his mates Dad had removed the guard cause it was in the way! I hit the farking roof at the Christmas table!!

He is my nephew by marriage and my wife is the youngest of 4 girls and this young fella did not have a dad so no male figure. I am that guy now. My sister inlaw's all just looked at me. No idea. Needless to say he never used the grinder again. His friends Dad should be bloody shot!! D1ckhead! Right there!

Thanks for the post. Good male mentors is what's wrong with our society.....not enough that care.

[kevin07]

Caught a cock head on site (lucky for him) had a cut quick blade (14") worn down and was attempting to put it in a 7". Quick cut blades are rated for 4400rpm 7" grinder 8600rpm. No visor nadda it would have blown apart at 8600 rpm would have been nasty.


Have a google of Angle grinder injuries PHARKN NASTY!!
best one I saw was a bloke put a 14 inch tungsten blade in a quick cut for cutting old sleepers he didn't run out of luck that time but im sure he would have sooner or later

[kevin07]

The 9inch is a monster of a tool. I can see why they have been banned.

I wonder how the old 12 inch grinders are going at the hire company I worked for an extremely popular item.

[taslucas]

A general rule for cutting aluminum is to treat it as wood instead of metal and use wood tools like a toothed blade on a drop saw as mudrunner said.
A mate pushed his alloy bullbar onto his wheel when his 4x4 hit a tree and used a chainsaw to cut it off. Natural reaction from people was that it's a crazy idea but it works better and safer than a grinder with surprisingly little wear on the chain.

[threedogs]

Can see that working as it would be throwing pieces of alloy out and not clogging the blade.
Good out come in an emergency situation, Blades are what $30 each,

[taslucas]

Yeah the chain really didnt wear that much at all. A sharpen up and it was as good as new. Probably about the same as 3 loads of wood worth of wear

[threedogs]

@ Growler I've been out of the work environment for twenty years.
I would think the wrap around clear visor is the correct protection.
Seema goggles fog up too easy

@ lucas it must have made a terrible racket

[Shaun 4x4]

I work in an aluminum ship building factory.
We use grinders all day every day to cut aluminum and in my 7 years ive never had a single disk shatter.
Maybe we have a different type of disk but they look like a normal one to me.
Can take a picture of them on monday if you like?

Also we are one of the only places that still use millers.
Quite a scary tool imo. Its like a 5" circular saw blade in a grider with the lock buttom removed to be push and hold.
But they cut through 12mm ali plate like it butter!

[megatexture]

Never had a 9"grinder kick back yet, 4" yes but usually from grinding/ cutting something at a awkward angle or pushing to hard though I only cut concrete with my 9"

[growler2058]

@ Growler I've been out of the work environment for twenty years.
I would think the wrap around clear visor is the correct protection.
Seema goggles fog up too easy


Yup we have em which attach to hard hats


Never had a 9"grinder kick back yet, 4" yes but usually from grinding/ cutting something at a awkward angle or pushing to hard though I only cut concrete with my 9"



Wouldn't get away with dry cutting conc on one of our sites, the dust coppers would shut ya down reeeeeeel fast

[megatexture]

Thats why we stick to residential not worth my Time doing commercial, to many high strung morons and delays on site

[growler2058]

Thats why we stick to residential not worth my Time doing commercial, to many high strung morons and delays on site


HAhahahhahahahaha that's why I got away from resi :)

[megatexture]

Lol were never on site with any other trades and mostly doing renovations also

[threedogs]

Thank God for all this OH&S there would be a lot more kids without fathers if not for it.
Thinking back on some of the things we were made to do or sacked and some we did just to finish the job
makes me shiver. No way breathing would I do or even attempt to do now, working a lot out bush made you able to come up with heaps
of alternatives, and never waste a thing.

[taslucas]

HAhahahhahahahaha that's why I got away from resi :)

.....and became a high strung safety moron! Lmao

[taslucas]

@ lucas it must have made a terrible racket

Yes it sounds like a screaming banshee ripping your ear drum open

[growler2058]

.....and became a high strung safety moron! Lmao





You forgot highly overpaid :)

[taslucas]

You forgot highly overpaid :)

And I also forgot overly modest

[Winnie]

Yeah the chain really didnt wear that much at all. A sharpen up and it was as good as new. Probably about the same as 3 loads of wood worth of wear

When Kris did that with his mav we used a hacksaw to cut it off in the middle of the night ahaha

[93patrol]

to cut some roof sheeting i have used the 7 and 1/4 circular saw with the blade turned backwards so the teeth don't grab the sheet and end up tearing it works really good

[threedogs]

With this maybe this thread can be closed

[sil3nt_dr3ams]

I always wear gloves using my grinders handles and guards always fitted no homemade attachments like a die grinder shafts or modified 9 inch guards.




http://www.nissanpatrol.com.au/forums/images/imported/2013/12/123.jpg

Might have told a few lies there,

9inch grinders are the most awsome tool when matched to the appropriate job. A 9inch grinder is only dangerous in a idiots hands other than that its a brilliant tool. Some site wont allow us with 9 inches on it so we just swap the 9 inch guard with a 7 1/4 guard.

[NP99]

I can never find my disc spanner when I need it.....

[megatexture]

apart from my 9" i just finger tight them up and twist the blade to tighten more.

[NP99]

I bought some Bosch 125 cutting blades from Masters. They are are quality disc, never again discs from trade tools!

[Woof]

I have a 4,5 and 9 in angle grinders and recently had trouble using the 4in doing some cutting jobs. The discs shattered and broke pretty easy. The job was just cutting some aluminium posts.

After researching the web and reading about some of my bad habits which I wasn't aware of, I thought this the place to ask of those in the trade.

What disc for what job and how to apply disc size and wattage of the grinder to a particular job.

Also read that the 9in grinders have been banned on worksites!

Should have found this before I tried yesterday, bits flew everywhere......................just got a tungsten carbide tipped metal disc to try, looks bloody aggressive though