Using an angle grinder as a bench grinder

angle-grinder-bench-grinder

[Saeid Momtahan] made a couple of attachments that let him use his angle grinder as a bench grinder. It may be better to refer to it as a bench motor, as he uses both a grinding wheel and a wire brush while showing off his project.

The attachments come in two parts. The first is a piece of square tube that runs parallel to the body of the grinder on the side opposite the handle. This doubles as a larger gripping area when using it as an angle grinder, as well as giving him something to clamp in his bench vise. The second attachment serves as a rest for the work piece. Above you can see him brushing some rusty stock clean with the wire attachment.

It’s nice to have the option of doubling up a tool’s tasks rather than buying yet another item that may not get used all that much. We also love the idea of building your own tools. If you don’t have a welding rig to fabricate these add-ons here’s a li-ion battery based system to get you thinking.

[Thanks Rob]

55 thoughts on “Using an angle grinder as a bench grinder

  1. Are you supposed to wear gloves with power tools? It was my understanding if the cloth gets caught your hand gets mangled, while if it hits skin you get cut but you don’t get pulled in.

    1. The rule of thumb I learned was to wear tight protective clothing. It’s the loose stuff that gets caught when you aren’t looking. And in this case, since grinding tends to generate a lot of heat, holding a metal piece bare handed probably isn’t an option.

      1. Ah I see. It’s a Pete peeve of mine when A-Lister actors are wearing big baggy gloves while using a bench saw or similar in movies

      2. @mikemac

        The proper shop safety practice is no gloves when using grinders, sanders, etc. Anything that can grab a glove and mangle your hand is bad news.

        You describe the motivation for wanting to break this rule which is where the rule came from in the first place.

      3. Do NOT wear protective outfits where there’s a risk that the tool you’re using can grab it. That’s everything with saw blades and anything that has a slot with stuff turning in it. It will grab your glove and pull the rest into the machine since it can’t cut through the cloth it pulls instead.

        1. I’ve got a modified extension cable for using my grinders (and any applicable power tool) that has an inline foot switch with a velcro tab that wraps around my boot.
          So if I’m not contacting it, the grinder gets no power.
          When it’s snagging on something and it’s got no power, it spins down pretty rapidly.

          1. I can guarantee your power tool can take off one of your fingers both before your foot comes off the switch, and it spins down.

    2. Supposedly, wire brushes can throw off bits of the wires that get under the skin. I think if you’re planning on getting close enough to the grinder with your hands that being pulled in is a risk then you should consider holding the work in something.

    3. My dad’s fingers were saved by a pair of thin welding gloves when he got too close to a band saw blade. The leather bound up the blade and kept it from removing his fingers. Still needed a shit ton of stitches. Remember everybody, PUSH STICKS!!

      1. Or use half a brain and not stick your parts that close to moving objects to begin with. I don’t think I have ever met someone that had removed limbs themselves that had much common sense.

        1. It isn’t so much about sense as it is getting caught up in the moment. People tend to realize they made a stupid mistake after they did it, even without injury. That’s why it is so important that safety isn’t something you also pay attention to, safety must be grilled right into your muscle memory from day one. If you have to think ‘be safe’ it’s only a matter of time until you get so excited or frustrated by some piece of work that you get careless.

        2. In his 30 years of teaching, that was the second worst accident he ever had. First worst was with a welder one of the students messed up. Had a mig gun basically explode in his hand. Arced across his knuckles, and blackened some skin. Only takes a second for anybody to hurt themselves with power tools.

        3. Ever had a table saw get pinched by a piece of hardwood and nearly have your throat cut by the saw blade? Power tools themselves may be predictable in their action, but materials being cut are not. Ever had a piece of plexiglass break on a table saw and shoot across the room and stick into the wall? I have seen that happen before. Ever had a piece of steel get caught in your grinder and cause the grinding stone to shatter? Have never seen this but it’s been known to happen.

    4. Depends on what it is you work with. If you regularly work with really sharp edges or very hot materials, it’s probably a good idea to wear calfskin or kangaroo leather gloves. If you work a forge or a stamp, gloves are a must.

      If you work with tools that spin really fast with a lot of inertia, and there’s any chance of something getting caught, probably better to go bare-handed or use gloves that can easily tear away (say, neoprene or latex).

      1. Did you know Kangaroos can go 70 km/h (44 mph) for short distances? Just read that the other day..
        Useless factoid but hey – you mentioned kangaroos “)

    5. No, never wear gloves. Use pliers or vise grips if it get hot or cool it with water periodically. No clothing, loose or tight should ever be permitted around a grinder or any rotating machinery, this applies to lathes, mills, drill presses, sanders. Anything.

      1. Sorry but gloves are not classed as “loose clothing” when it comes to working in a metal shop and not wearing them will quickly get you marched off most sites in the country.

        The trick is using the correct gloves for the job. Wearing loose fitting XXL welding gloves then you’re asking for trouble. The right gloves for grinding are tight fitting rigging gloves which are about as loose fitting as a spandex bodysuit on a fat person.

        1. Oy, yes they are. Even the tightest gloves will wrap you up faster than you can think. OSHA rules prohibit gloves in these situations.

          Even tight “weak” gloves like nitrile gloves are still strong enough to pull you into work.

          1. Appropriately fitting gloves should be worn when using portable power tools. However, gloves are to not be worn for stationary equipment like lathes, mills, bandsaws, and bench grinders. Usually the tool manual will say if gloves should or should not be worn.

          2. Nitrile and latex gloves can pull you in, I wear them in the workshop (am a mechanic) and when I use an impact gun and steady the socket with my hand occationally the gloves will snag and pull onto the socket, most of the time its meerly an inconvenience but occationally it can tug your fingers or wrist properly hard in an unnatural direction, luckilly an impact gun actually has little inertia but sod going near a lathe…

    6. If two hands are kept on a grinder at all times, there shouldn’t be an issue with gloves getting caught in the tool. I had a lucky escape on one occasion when using a grinder while tired. My finger got caught between the disk and guard and then was spun out the far side – luckily in one piece! On another occasion a 9 inch grinder threw a short piece of 1 inch box which skimmed along the back of my hand slitting it. If I was wearing gloves, my hand wouldn’t have been cut. So wear gloves. As regards the hack above, the hands look too close to the brush for comfort on such a short piece of box.Also if a grinding disk is used, the guard wouldn’t give any protection against a shattered disk.

  2. Yes….gloves around power tools is a dangerous practice. Particularly in THIS instance where he is using a wire brush. The wires will grab the glove quite easily. This is not the first dangerous video I’ve seen on Hackaday, but I guess until you loose a finger people don’t learn. I hope the new site they are launching will give a little more consideration to the demonstrations in the videos they post because spreading bad and dangerous practices is really in irresponsible thing to do.

    1. I remember a physics lab exercise with liquid nitrogen.

      The lab assistant had a 10 minute lecture as to why gloves were dangerous around liquid nitrogen (it soaks into the gloves and cools the skin as opposed to just flowing off the skin)

      They had gloves laid out on the benches however, and i guess it was some kind of test to see who had listened to the lecture…

      1. There are gloves specifically made for LN2, that is probably what those gloves were. Its best to teach not to use gloves because the chances of people having the right ones is pretty slim.

  3. I saw this on YouTube a couple of weeks ago. Honestly, the more I think about it the less I see the point. I guess if all you have is an angle grinder and you happen to have some metal stock and a welding setup on hand, this would be a good idea as a cost-saving measure.

    But, there are so many safer and more straightforward ways to go about this. I’d rather not use a handheld grinder on the bench for the same reason I trust bolts more than a vise.

  4. Did anyone spot the state of that wood after he’d finished sanding it? Not really the finish you’re looking for, that angle grinder is either spinning too fast or he’s pushing too hard on it, either way I don’t think he really knows what he’s doing.

    You really shouldn’t mess around with that kind of thing putting the wrong blades/heads on them, it’s just an accident waiting to happen. You’re not saving any time at all if a mod ends up taking your last breath, in fact you will have wasted your last bit of time on this earth with a stupid mod and earning a darwin award.

    1. It is the wrong kind of wheel for wood. Wood requires an open sandpaper like surface where the sawdust and resins take longer to accumulate. Wheels for metal are too dense and the wood packs in, get hot, and starts burning. And the often do run too fast.

  5. One other thing, the fiber reinforced wheels have been know to frag and kill or severely wound people. Thats why there is a guard around it protecting the operator. Standing in front of it makes the guard pretty useless.

  6. I love the ingenuity displayed on this, well done!

    But I will say, second hand bench grinders usually go for $20-30. Heck, new ones go for $40. These usually include safety shields, and proper mounts, etc. Then you can keep your angle grinder to use as an angle grinder

    1. He said in the video that he has a bench grinder, it’s all about saving time by the looks of things. He has got a full face guard on though, so he can have an open casket if he wants.

  7. Since we seem to be having another ‘safety fest’, lets consider the phrase: “Using the right tool for the job” (which this clearly is NOT).

    Honestly, for the price of even a *cheap* bench grinder (maybe 50 bucks at the most? What does Harbor Freight charge these days?), I have no idea why you’d do this, unless you want to loose some fingers.

  8. Angle grinders have very weak bearings. Ok for disc use, but never with wire brush like that. Imbalance will kill them quickly.
    And yes, I have a killed Bosh angle grinder…

  9. One thing makes angle grinder totally unusable as bench motor. Noise. Somebody who will invent cheap and quiet beveled gearing should achieve Nobel Prize. For powering tools any scavenged motor will do better. However cheap tools are great source of fasteners for standard blades, discs, brushes etc.

  10. The timing of this post is impeccable, I’ve seen 2 news stories this week about mishaps with angle grinders and the utterly stupid things people did.

    1. A british guy was having trouble with a tree stump in his garden, his chainsaw wasn’t playing ball, so he decided that putting a circular saw blade in an angle grinder, he attempted to cut the tree stump out with his contraption, it was the last bit of DIY he ever did, he got massive kickback and hit himself in the neck and severed his major arteries, his wife found him in a pool of blood in his back garden. Tragic and stupid all at the same time.

    2. A farmer in south america, did pretty much the same thing, angle grinder, circular saw blade, this time though, he wasn’t trying to remove tree stumps, he was chopping firewood with it, got kickback, ended up with the blade embedded 10cm into his stomach, incredibly, he missed all of his organs and managed to drive himself to hospital where he was treated, he survived but swears he won’t go near power tools again.

  11. Bench grinders can be terribly cheap on sale, All I can think of is this thing slipping out of the vice and running right up this guys chest and taking off his face. Angle grinders are wayyyy faster than bench grinders and the way you hold them kind of makes you stand to the side, which is a good thing. I’d hate to see what happens when the stone shreds on this thing…

    1. Also, why is it that pretty much every post about “power tools” on this site features someone doing something extremely stupid and unsafe with something that wasn’t designed for its new purpose? I get “HACK a day”, but taking a tool that was purposely designed for a certain job and using it for something completely stupid is not a hack. How about someone “hacking in” some safety into something that was once unsafe for a change? I guess smart people doing safe things doesn’t make for good youtube or darwin awards and obviously HAD posts…

  12. I had a couple weeks long workshop training at a local college a few years ago. They have these massive classes with ~20 mills, lathes etc in. They had pictures up everywhere taken from injuries that took place in the class because of people not being safety concious.

    The ones I remember the most was one of an eye that had one of those wire bristles stuck in, right next to the iris. So now I *always* wear goggles. Then there was this other picture… We believe it was fake, but who knows. It was basically a massive lathe covered in blood and gore and torn clothing. It clearly looked like someone got caught in the machine and things went south from there on. Pictures like those force you to learn a different level of respect for large machines like that.

  13. I always wear gloves when grinding with an angle grinder. NEVER when using a bench grinder.

    Safety video on angle grinder showing proper use of PPE including gloves:

    1. I’ll add to this…

      With hand tools you bring the tool to the workpiece. Using an angle grinder you should be gripping it with two hands in the proper places and so your hands/gloves should never get near the wheel. I like gloves to protect me from flying debris and also should my hands bump into a sharp piece of metal. (that stationary piece of metal won’t pull your glove into it, but it’ll sure cut up the back of your hand)

      With stationary tools you bring the workpiece to the tool and your hands get close to the spinning parts. Gloves could get snagged so you should not wear them.

      Since this guy is bringing the workpiece to the tool, I’d say this is a case where you do NOT want to wear gloves.

  14. A 5″ makita angle grinder spins at 10000 RPM, a 6″ at about 11000 a 6″ bench grinder spins at about 1700, big difference. This guy is an idiot, end of story. Use your tool for its intended use. Also NOT wearing gloves while using an angle grinder is also stupid, the biggest risk from getting hurt while using one is strings in your hoodie, and improper use resulting in kickback.

    /Redseal Journeyman Welder
    //Seen injuries listed above, buffing wheel attachment caught in grinder striings mangled a persons face. Improper use resulting in kick back with a 10″ grinder resulted in me being able to see into a person nasal cavity, guy lost his eye.

  15. It’s a brilliant design. Get over it guys. It’s simple and genius. Please, be careful not to poke yourselves in the eye with your fork while eating.

    1. Yes it is an excellent idea and all these replies are from a bunch of idiots who can’t see that. I did something very similar after leaving it around a couple of years. People are missing the point that these grinders are cheap and powerful. Best of luck.

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