The Does and Don'ts of using an angle grinder...

[Mod30]

This is thanks to Another FrankenBurner on another thread.

I regularly use an angle grinder with an abrasive cutoff wheel.  I also use grinding wheels, flap discs, and cup brushes.  If I were to start a new smithy with limited funds, it would be the first electric tool I purchased.  I own several.  

I use them in my trade as well, so I have hours and hours of experience using them.  I do not fear using them but I keep a healthy respect.  Are there risks involved in using them, yes.  Understanding these risks, helps with safety.  It does not eliminate the risks, it makes you work differently to mitigate them.

My advice if you are new to angle grinders:  

• If you know someone who has experience and can show you the ropes, it's worth asking.  So long as they are safety conscious.  A lot of guys are careless in their use.  They get away with it until they don't.
• Buy a regular powered model, not the new high torque models.  I would rather have a tool that jams to a stop when torqued funny, than one which has enough power to keep on spinning. 
• Never use a diamond coated cutoff wheel.  When torqued funny, an abrasive wheel will shatter which is better than a steel wheel which could instead torque the tool out of your hands and keep on spinning. 
• Never use cheap abrasive wheels as they tend to shatter easier than better wheels.  The less shattering the better.  Never use cracked, frayed, or damaged wheels for the same reason.  
• Don't put a 6 inch wheel on a 4 1/2" angle grinder.  
• Make sure the max RPM of your intended accessory is rated higher than the RPM of your grinder.  I have seen cup brushes rated well below the standard grinder RPM even though they have the proper mount for the standard grinder.
• Never stand inline with the cutoff wheel when cutting.  People tend to sight down the wheel for cutting straight lines.  If the wheel shatters, you don't want to be in that lineup.
• Never put a sideways pressure on the cutoff wheel.  The cutoff wheel is not a grinding wheel.  The cutoff is designed to cut straight linear cuts.  You risk shattering the disk by pressing it sideways.  
• Never take the guard off.  Not only does it guard you from shattering discs, it prevents you from sticking your fingers into the backside of the wheel, and it directs the sparks away from you when cutting.  I am surprised how often I see this problem. 
• Whenever possible, use the side handle.  It is more ergonomic giving a better less fatiguing grip and two hands are better than one.
• Wear your PPE.  For me this is generally goggles, muffs, and respirator.  I also like a leather apron to save my shirts/pants from sparks.  Some of my co workers like gloves.  I don't personally as I prefer a better grip.  
• No loose clothing.  If something loose gets caught up in the grinder, the grinder winds it up.  Sometimes pulling the grinder into the clothing.  Imagine a loose t shirt, the grinder could pull itself straight into the belly/chest.  The cup brushes are more likely to grab something this way than discs.
• Don't death grip the tool but always assume it could attempt to lurch forward at any moment.  Think loose but secure grip.
• Never put muscle into it.  Let the tool do the job.  You are there to guide the tool.  Extra pressure will make it cut faster.  It will also wear you out faster, wear the wheel out faster, and makes it easier to jam the wheel either sideways in which case the wheel can shatter or inline which can cause the tool to lurch forward potentially out of your hands.  At first, I recommend light pressure.  Get used to how the tool moves and how this makes it try to move.  The angle grinder wheel spins clockwise when viewed from above, this causes it to pull forward when cutting with the wheel in a vertical orientation or kick to the left when the wheel is oriented horizontally.  You have to counter these movements.  The more pressure you push the tool into the metal, the more power the movement will have.
• If you are fatigued, put the tool down.  

It sounds scary maybe.  So does an orange piece of metal to those who don't play with them.  I use my angle grinders regularly without hesitation.  

All that said, if I can cut it with the band saw, I will do that before the grinder.  Less noise and dust.  The exception being harder metals.  I would rather waste a cutoff disc than a bandsaw blade.  If I can grind it on the belt grinder, I will.  Even clean grinding is much easier than with a small rotating disc.  I also use a jig saw, sawzall, and a plasma cutter for cutting depending on what I am cutting, though they come out less often.

If I could have only one electric tool as a general blacksmith, it would probably be a 4 1/2" angle grinder.  You can cut, grind, and polish with one tool.

[Stash]

Ive been using diamond blades for cutting metal for 8+ years and for cutting masonry for over 20 years. Never had an issue 'torquing out' of a cut uncontrollably. I prefer paddle switches on the handle- sort of a built in deadman control so this could help. I've decided I don't care for blades shattering that close to me so I made the switch to the diamond blades. Never had a problem that caused a code brown  moment, and I still have a pile of unused, un needed abrasive zip discs in my grinder boxes. YMMV

Steve

[Deimos]

Something almost nobody knows, all disks have a date stamped into the metal, that is an expiration date. DO NOT use the disk after that date, there is a good chance that the resin is not up to snuff and the disk will turn into a shotgun (found that one out the hard way)

[rustyanchor]

I did not know that. I probably really need to check my supply's dates.

An angle grinder with a twisted wire wheel is a wonderful tool that will eat your lunch, real quick, if you don't pay attention.

Edited March 3, 2021 by Mod30
Remove excessive quote.

[Another FrankenBurner]

I wrote the above to be the other side of the coin.  Several members had mentioned their fear of using an angle grinder, in some cases avoiding them completely as they are too dangerous.  I get it, lots of people are killed/injured every year by 4 1/2" angle grinders.  I wanted to show that with proper knowledge/precaution, angle grinders are a great tool to have. 

As I know it, the biggest two causes of injury are having a type 1 bonded cut off disc explode throwing chunks at the operator and losing control because of kick back.  Both of which, if anticipated, can be minimized.  

As to the cutoff disc exploding, leave the guard on the unit.  DON'T RUN CHEAP WHEELS, as though your life could depend on it.  Don't run the 6" cut off wheels on the 4 1/2" angle grinder.  Generally the 6" wheels are rated at 10,000 ish RPM maximum and the 4 1/2" angle grinders run faster than that.  If you need encouragement, do a search of angle grinder accidents.  You will see horrible images of partial wheels sticking out of faces.  Hard to forget images.

I should not have used the word never with the diamond cut off discs.  I was warned to not use them at first until I got the hang of the angle grinder.  I use them and prefer them as they are statistically safer because they don't explode.  I also like the lesser dust created.  I have never had one bind/kick and get away from me but I can see the logic behind the warning I was given.  

I prefer the way the bonded disc cuts and have only had one disc explode which was because of how I was using it.  I had the guard on, my PPE on, I was not inline with the wheel so instead of injuring myself potentially horribly, I put on another disc and went back to work, a bit more carefully.  After a bit of experience, you learn to cut by feel.  You can feel when you are twisting/flexing the wheel, when it starts to become trapped by the cut piece bending, and when you are cutting against an edge.  You learn the most efficient way to cut which mostly prevents kick back and wheel shatter, and doesn't wear the wheel out nearly as fast.  

When it comes to kick back, think about how you are cutting, how the wheel is rotating and if it does kick, which way it is going to go.  Cut in a way that makes it so the kick direction is away from you.  If the sparks are flying your way, the tool will kick away from you.  Then you can just hold onto it and nothing bad happens.  The side handle is great for this.  As Stash said above, a trigger or paddle switch is great in that if the grinder did happen to get away from you, it would shut off.  

Fix the piece you are cutting.  Don't try to hold the piece in one hand and the grinder in the other.  You could lose fingers or turn the piece into a projectile pretty easily.  

Angle grinders are running a high RPM with a big wheel.  They can change things very quickly which is why they are so great but also so potentially dangerous.  It only takes one bad moment or one stupid thing to really change what you have going on.  Treat them as such so you don't get too comfortable and they are a great tool.

Deimos, thank you for that.  I had no idea either.

 

[Frosty]

Oooh there are some ugly wound pictures!

I was looking through a number and came to a pretty typical youtube how to video. A gal was setting up a new chainsaw chain disk on her grinder and did a whole bunch of talking about the thing while she reversed the chain and installed it. Happily it barely scraped the wood she was "carving?" If she'd had it installed properly and it cut like it should it would've been jerked out of her hands and gone walk about. The angle grinder she was using had a switch so it would've kept running until it pulled or cut  the cord if a survivor didn't unplug it. 

Those were some scary videos a guy shouldn't be able to see the tendons working when he moves his fingers. 

Frosty The Lucky.

[Another FrankenBurner]

Sorry Frosty, I had to put that out there.  Those pictures/videos are rough enough that they might make an impact on would be careless grinder operators.  

I've never messed with those gnarly looking chainsaw attachments.  The small round ones or the bar attachments.  They are a neat carving attachment but I see myself regretting using one.  They just seem too aggressive for such a lightweight powerful tool.  I've heard enough horror stories of chainsaw kickback with full size heavy saws.  I'm sure some folks use and love them.  

[Stash]

I have one of those chainsaw chain carvers, I don't think I have 15 mins total on it. It is hard to get past the pucker factor, so I pick it up, look at it a while and then put it away. I have other carving attachments that work well, aren't real aggressive and I can work safely. They are made with a kind of self-limiting construction, like the anti- kickback feature on the newer saw chains. You still need to pay attention and keep a firm grip with BOTH hands.

Steve

[Will-I-am]

The safest way to carve with a chainsaw is with a "dime tip", very little kickback.  A normal chainsaw can be converted with a dime tip bar kit; or what I did is buy a rechargeable stihl chainsaw with a dime tip.  Their cheapest model is $300 and works excellent.  Get 45 minutes of fun before recharging, by then you are tired.

[SinDoc]

I have seen first hand what a shattered grinding disc can do to a person. I was the lucky individual to rush a person to the ER from work who had a piece sticking out of his forehead. I have also seen safety glasses save someone's eyes, as when the disc exploded, it lodged into the glasses instead of their eye. Scary stuff. I personally don't mind angle grinders, but am very cautious with it while using one. Circular saws on the other hand, I bought a small one a few years ago to help build my shed. It is still in the box. Fully taped. I am too afraid of them to even unbox it to try using it.

[Frosty]

One of the things my Father used to tell us until we were sick of hearing it is as true as words get. "You have to respect it but you can't be afraid of it." The "it" being whatever tool or job you're doing. If you're afraid of a circular saw then in the box is where it should stay until you can get it out of your place. It should sell pretty well being in the unopened box. Not for new price of course but I'd ask 75% and be willing to bargain. 

If you keep it around a time may come when you decide to use a tool that scares you and that's when things can go B A D. If you're afraid it's really hard not to focus on things that can go wrong and nothing guarantees a thing will go wrong like focusing on that thing.

I'm not giving you a hard time, I think you're doing the right thing and am behind you all the way. Not using it is a smart thing to do. . . . Not do?

Frosty The Lucky.

[SinDoc]

Funny part is while I am much too nervous to use a circular saw, I use miters, table top and chain saws all the time 

[ThomasPowers]

I have a friend who, in separate accidents 11 years apart IIRC, cut off his forefingers using a table saw.  After the second re-attachment; His wife would not allow him to use a table saw anymore.  However she had no problem with him running a foundry and casting brass!  He claims that his forefinger is now an exact number of inches and he can use it for measuring.  His friends worry about when he goes metric!

[pnut]

Have you seen the table saws with the safety brake that stops them if they hit flesh. I watched a demo of a hot dog stopping it? Didn't even break the casing. 

Pnut

[Glenn]

Those table saw brakes are a one time use item and are expensive.  Not as expensive as a visit to the hospital emergency room and a doctor, so if you are going to put a finger into a table saw blade, the expense if well worth the investment.

Wire wheels on a grinder are a whole different story.  They will eat you, your clothes, and your body, you just do not know when.  They throw wires like daggers with pinpoint accuracy (pun intended).  

The 4-1/2 inch grinder is a tool for small projects or details.  When you move up to a 7 inch or a 9 inch grinder the difference is multiplied by exponents.  They are designed for larger projects and EAT metal.  You can not turn it loose fast enough, and the run down to stop time is measured in minutes.  All safety rules are to be followed. It is no longer a matter of talking about an injury, but show and tell time for missing parts.

If you take anything away from this discussion, ALWAYS run the disk or wheel OFF the metal.  Never run the disk or wheel on to the metal as it WILL grab onto and bite into the metal and take the tool out of your hands.

[pnut]

12 minutes ago, Glenn said:

Those table saw brakes are a one time use item and are expensive.  Not as expensive as a visit to the hospital emergency room and a doctor, so if you are going to put a finger into a table saw blade, the expense if well worth the investment.

Definitely doesn't do anything good for the tool. I watched a slo mo video and the torque when it stopped was pretty amazing. 

Pnut

[Anachronist58]

Some folks walk on steel beams high above the ground.  I once walked beams on commercial tilt-ups. I am no longer qualified for such work.  Not everyone should be licensed to operate motor vehicles on public roadways. Not everyone is qualified to operate a barbecue grill.  If we desire to operate equipment that may cause injury or death, we must be able to assess our depth, and work our way prudently as we develop our skills and take on additional risks.  There are operations that I am able to perform safely, that I will never describe on an open forum; operating an angle grinder with a 4-½" cutoff disc not amongst them....

A healthy respect for dangerous things never hurt anyone .

Robert Taylor

[Frosty]

Glenn: The spin down time of a 9" Milwaukee disk grinder is about 20 seconds, not "minutes" and not that much longer than my 7". 

When you say 

6 hours ago, Glenn said:

If you take anything away from this discussion, ALWAYS run the disk or wheel OFF the metal.  Never run the disk or wheel on to the metal as it WILL grab onto and bite into the metal and take the tool out of your hands.

Do you mean take the disk off the metal BEFORE you let go of the trigger? If so that is a BIG YES. The motor torques hard when you turn it on or off and if the disk is in a cut it WILL bid and jerk YOU through the cut. I have a scar to show for making that mistake. Stop BEFORE you get tired!

And never let go of a disk grinder until it's stopped completely. 

Frosty The Lucky.

[Glenn]

Let the grinder spin up before you touch it to the work.

Lift the grinder away from the work when you finish and then let it spin down. 

When actually doing the work, always move the grinder toward the edge and off the work.  If you move the grinder toward the edge of the work, it will catch on the edge and bad things can happen.

Sorry for the confusion.  Thanks for catching it Frosty.

[SinDoc]

As my late grandfather would say after losing the tips off all his fingers on his left hand, make sure when using any kind of cutting tool that your workplace is nice and clean. He cut his finger tips off after he tripped over scrap on the floor while running his saw and fell hand first into the blade. Grandma wasn't very happy when he came walking in with this...bits...in a baggy and said he thinks its time to go to the ER 

[ThomasPowers]

Wives, Partners, Significant Others, never are happy in those situations!

[Frosty]

Of course Glenn, just trying to do my part. 

Lets hope so Thomas!

Frosty The Lucky.

[Irondragon Forge ClayWorks]

When I come in from the shop with a paper towel or rag in my hand, my wife says "are you bleeding"? She makes a very good nurse.

[ThomasPowers]

Proverbial "dirty shop rag".

[Glenn]

You can never wipe anything cleaner than what the rag is dirty.