View Full Version : Cutoff disc in a die grinder - is it safe?

05-21-2005, 07:13 PM
I saw a packaged set of an arbor and cutoff disc up at Lowes. It said it was for a cutoff tool or a die grinder.

Is it safe to use something like this in a die grinder since there isn't any guard like a cutoff tool has?


05-21-2005, 07:20 PM
"Is it safe?"
Sure should be, but depends on the user I suppose.

Mine hasn't maimed me yet. I have another one with a guard that I seldom use. You do have to watch where you are throwing the sparks though. My chainsaw doesn't have any kind of guard and it worries me a whole lot more.

05-21-2005, 07:23 PM
I use them all the time. Don't get your face over the wheel. When they brake the parts of the wheel usually get stuck in the ceiling insulation.

05-21-2005, 07:23 PM
I would keep it slow under 6000 rpm maybe to be on the safe side
bet the cut off disc is rated at 10,000 max
your die grinder is capable of 30,000 rpm.
take care
all the best..mark

05-21-2005, 08:08 PM
Well I'm going to open by saying it is not safe.

Some history to my stance on this.

I worked in a shop were they did not have guards on any grinders when I started there. I asked othes about this and no one wanted them, so I shut up about it.

One day a fellow worker was using a cut off and it kicked back, twisted around and sliced through his wrist before it stopped. Well they had a terrable time fixing his hand back on and all the grinding crap from the cutoff disk didn't help. Was off work about 6 months.

When he came back I again persued the re enstatement of guards again and succeded.

Now a die grinder may not have the power of the machine he was using, but even so could inflict a nasty cut/burn.

So I would put in a couple of proviso's. Need's a suitable guard to protect the user from the wheel and also make sure the cutoff wheel is rated for the speed of the die grinder.


05-21-2005, 08:49 PM
Are they safe? little over a year ago i'd said yes. that was before a friend called me to say another friend had died. seems Dennis was using a cutoff wheel and for some reason it exploded, a piece went through his chest and into his heart. they said he made it about 20 feet before he colapsed and died.
now do i still use them? yes, but with a lot of new found respect.
stay safe, jim

Gordon Campbell
05-21-2005, 09:41 PM
pgmrdan : I have used them on boiler work for a lot of years.
In some situations a grinder guard cannot be used. I have never had any problems. I also wear a hard hat with full
face shield and tig or heavy arc welding
Gordon Campbell

05-21-2005, 10:01 PM
Safe? The tool is safe, is the operator though?

Tools, being machines can become hazardous in the wrong hands.

Using a cutoff wheel in a die grinder, and I will assume it's an air die grinder, works just fine. The operator should wear full safety gear such as hearing protection, full face shield, long sleeved shirt or jacket, pants/shoes, leather gloves and a fire extinguisher, all at a minimum.

Now, if you are talking about a nice Milwaukee or similar electric die grinder I would opt against it, unless you use a variable speed control for the grinder. Air units are easy enough to control the rpm using the throttle or for smaller units just working them harder.

Electric units are usually single speed and quite fast (+30,000 rpm). Larger electric grinders may be spec'ed for the large 3" grinding wheel at full GO but most smaller hand held electric die grinders are not rated at full rpm with a 3" wheel and there starts the safety issue.

You can compensate for this with an inexpensive speed control usually used for wood routers. Many electric die grinders use ac/dc or "universal" electric motors which can be speed controlled cheaply.


05-22-2005, 11:53 AM
nothing is safe. if it was we would never get ant thing done. no mater what you are doing there is always some one that has died or been injured doing it like getting out of the bath tub.
you run more risk driving to and from work each day.

05-22-2005, 03:56 PM
a relation of mine was using a cutting disc to grind off a burr under a vehicle, the disc exploded and a large chunk embedded into his wrist, he was very lucky, his wrist was covering his face, he too was off work for months with the injury. there is only one safe working practice, use cutting discs for cutting and grinding discs for grinding NOT vise-versa..


05-22-2005, 03:58 PM
I use the same thing a work, just be careful about the direction of the spark path.

05-22-2005, 06:29 PM
After reading threads like this, I know WHY there has to be a safety department, safety engineers and safety trainning.

I recall being on a job once where one of the pipe welders was welding with the wrong polarity with (fleetweld 5P). I tried to tell him, but he wouldn't listen. Tried to tell me he's been welding for years and that I was full of ****.

On another job, a pipe welder was using 7018 and whipping the rod. Putting butt-loads porosity that you could easily see in the weld. Said that's the way he was taught. <duh> Course he didn't last long and probably still doing things "his way".

I've seen TIG welders weld tubing so hot that the tube ends up looking like an hourglass when thier finished. I've seen them weld with out a purge inside the tube and wonder why the weld had crystialized.

I remember when some guys on the job used to wash their dirty hands in Trichloroethylene to get them clean. Did it for years because "others" did it.

Oh, how about the "smart guy" that blows off his work clothes with oxygen from his cutting torch and then fires it up to light a cigarette.

How about the idiots that stress relieved the heavy wall pipe on powerhouses They put those Asbestos blankets over the electric blankets used to heat the pipe up. Of course, all this took place inside tent, just to make sure their lungs were full of Asbestos. I remember trying to tell them, but then again I was the freaking stupid one.

I've seen more than one welder that became a "welding inspector" after using the wrong RPM rated wheels on a die grinder, or even a side grinder and lost an eye. Oh, even while wearing safety shield and safety glasses.

Hell, there was even a guy in Vegas that lost his freaking nuts (those things between some of our legs) in a pipe machine. Had them real big super bag'ie pants on which got caught up in the machine and ripped those puppies right off. I tried to tell him to quit wearing the sweat shirt too that had those LONG laces hanging down for the hood ...... oh'well. Guess they'll call him HeShe now.


[This message has been edited by Smokedaddy (edited 05-22-2005).]

05-22-2005, 11:07 PM
I don't think that cut off wheels should be used in a grinder. These things explode (break-up and pieces go everywhere). Should you even thing that is the only way to do a task, wear plenty of safety equipment as some one else commented about.

I say don't do it. Find another way.

05-23-2005, 02:52 AM
<font face="Verdana, Arial" size="2">Originally posted by skeeter:
I don't think that cut off wheels should be used in a grinder. These things explode (break-up and pieces go everywhere). Should you even thing that is the only way to do a task, wear plenty of safety equipment as some one else commented about.

I say don't do it. Find another way.</font>

I don't have a problem with cutoff wheels used in grinders as there are wheels specialy made for that purpose on each size grinder. As long as you use the correct size and check that your grinder doesn't exceed the speed posted on the wheel. Leave the guard on! If you have to take it off to do the job, then there has to be a better way of doing it.

I can relate another grinder horror story. This was not using a cutoff wheel but a grinder doing grinding.

The users overalls had some holes with loose ends in the cruch area. Yes you guessed it, the wheel grabbed an end and wound it's way in. Fortunately it was not a powerfull grinder and it stalled before doing any serious damage to the person. But it did some how trap his hand in a way he could not release the switch on the grinder. He was in a real state, he dairnt move and it was still doing it's best to de knacker him. I had to unplug the grinder and help unravel it from his clothing. He was a very worried lad and it was a while before he could speak, walk or even smile.


05-23-2005, 07:26 AM
Yes it can be done, safely. It takes care and attention to disc speeds. (I use my welding helmet when I don't have a guard on a grinder).

It also takes 100% of your attention!

I've polished 316 SS marine work with a barrel grinder and 6" sisal mop. You can't use a guard. A single lapse of concentration and you are in a world of pain and/or expense. Them things do not have a trigger, they have a toggle switch.

Regard all the above good advice. Sit down and make the decision. Whatever you decide, and the decision IS yours, TAKE CARE MY FRIEND!
Your safety is in your hands.
Rgds, Lin.

05-24-2005, 08:27 PM
I consider cut off disks in die grinder safe until you "pop" the air to them. If the wheels are rated for the speed you are turning, they should not break just because of speed, unless damaged. A damaged wheel in an 1800 rpm bench grinder is dangerous too- under same conditions.

When I say "pop" the air I mean run them unloaded. Under load they bog down (I know there are exceptions but the exceptions seldom run on home shop air) if the wheel breaks or is jammed.

Remember, if a wheel (or anything else) breaks, or otherwise gets loose, the energy in wheel must be expended some how before it stops moving. The energy goes up directly as the weight of the moving object ( double the weight and you get double the energy) and it goes up as the speed squared (double speed, get 4 times the energy, triple speed is 9 times. 1800 squared is 324 time 10,000 (ten to the fourth power). 18000 squared is 324 times 1,000,000 (ten to the sixth power or a million) thats 100 times the energy if the weights are the same. but 100 4" cutoff wheels surely weigh as much as one 8" grinder wheel. I think, the energy in a breaking 4" cut off wheel at 18000 rpm (more for a 25,000 rpm grinder) is comparable to the of a 6 or 8 inch stone.

I've never had a cutoff wheel explode on me, but I don't rev them up to full speed with no load. and I keep the cutting plane away from my body if at all possible.

I doubt a face shield will stop a chunk of wheel coming directly from the grinder. I have heard stories of rebounded parts doing great damage- but I think there had to be more to the story than I was told. When the part hits something the thing it hits must be like rubber or better to rebound with much energy (an elastic collision). Most "collisions" are in-elastic. Some of the horror stories seem to violate the laws of physics.

I suggest keeping the wheels working to keep speed down, stay out of the line of fire, be aware of the power spinning out there at all times and use no guards- it will remind you to stay out of the line of fire if the wheel breaks.

My opinion is worth exactly what you pay for it- you think it out and be guided by your own conclusions.

05-24-2005, 08:37 PM
I'm going to buy a regular cut-off tool. You know, with the guard. http://bbs.homeshopmachinist.net//biggrin.gif

It sounds like it's not worth the risk to use a die grinder, IMHO.

05-24-2005, 08:39 PM

[This message has been edited by pgmrdan (edited 05-24-2005).]