What features should you look for?

Not all grinders are created equal when it comes to safety. About the only thing that’s standard on a grinder is the guard. And even then they’re different between manufacturers and models. OSHA says that a guard on a grinder is a requirement. There are exceptions to this rule, but for the most part you’re not likely to encounter them in everyday use. You can read about the requirements here [OSHA 29 CFR 1910.215 - Abrasive wheel machinery] and here [OSHA 29 CFR 1910.243 - Guarding of portable powered tools]. If a grinder doesn’t have a guard, it is to be taken out of service until it is repaired, i.e. a guard put back on it. The thing to look for in a guard is ease of use. A guard that’s hard to use will be more likely to be removed and not put back on. Some of the better grinders have guards that are easily adjusted by hand. And they stay in that position until you move them. Others require tools to position them, or move after you’ve positioned them by hand. There is a huge variance in quality of the guards between manufacturers. There isn’t much that’s more annoying than having to stop every few minutes to readjust a guard, not to mention unsafe.



One of the best safety features I’ve seen on a grinder is a safety clutch. As an example, I often use .040″-.045″ cutting wheels. These are excellent wheels for slicing through sheet metal or pipe, and when the conditions are perfect, they work very well. But the problem with them is that they’re prone to binding in the metal as you’re cutting. When this happens, it’s immediate and the grinder starts to rotate instead of the cutting wheel. This is a very dangerous situation known as kickback and it happens rather abruptly and violently. Especially if you’re not expecting it or not used to it. A safety clutch greatly reduces this and lessens the danger considerably. I’m really surprised that it’s not an OSHA requirement yet. I expect sometime it will be. It’s saved me hundreds of times.



Another great feature, although not very common yet, is the blade brake. Much like the brakes on wood miter saws, the blade brake stops the blade shortly after the power is shut off to the grinder. This is another feature that should also be an OSHA requirement. Since most grinders spin up to such a high RPM, the inertia of the wheel keeps them spinning for quite awhile after you shut them off. When you shut the power off, you often let your guard down, and can easily get nicked by a spinning wheel. It’s a pretty new feature, and I’ve only seen it on a few of the Metabo grinders.



Paddle switch or regular switch? I’m not a fan of paddle switches at all. As a matter of fact, i hate them. Some people like them, although i can’t understand why. There is usually a safety built into the paddle switches. A little spring loaded arm that stops the switch from being depressed. This is usually the first thing that breaks. Then, all you have to do is brush against the paddle switch to start the grinder. They also seem to require a more deliberate grip on the grinder. I’ve found that squeezing the paddle while holding on to the grinder wears out my hands sooner than a trigger switch or thumb switch. It’s harder to finesse a cut when you’re required to hold a grinder a certain way. If you’ve ever needed to prep a field weld, way up in the air for instance, you’ll understand this. I also can’t recall any paddle wheel grinders that you could lock on. Although this may have more to do with the way that i deliberately try to avoid them. With a thumb switch or a trigger you have the ability to lock it in the on position. This comes in really handy if you’ve got a lot of grinding to do. Your hands will get tired much sooner if you have to squeeze it constantly.



Variable speed is another feature that’s found on a few different grinders. It would be very useful when using a grinder as a buffer or polisher, since they require much lower operational speeds. There are also some wheels that require a slower speed, and metals that cut better at slower speeds. It’s a nice feature, but for normal use it’s not an absolute requirement.



On the electrical front, another great feature is soft start. This lets the grinder slowly ramp up to speed as opposed to starting at full power. This practically eliminates jerky, abrupt starts that can be dangerous. It also limits the inrush current to the motor helping to extend the life of the grinder. It’s a great feature that I’d highly recommend.



Ergonomics. A grinder is something you’ll become intimately familiar with. It’s completely hands on, and because of that you should be sure that you like the feel of the grinder. If it’s not comfortable to hold on to, you’ll hate using it. Grinders have come a long way in the past 20 years when it comes to fit and ergonomics. When they first came out, ergonomics were an afterthought. Today they’re smooth and contoured, and much consideration has been given to the feel. Something that’s comfortable to use and doesn’t tire you out quickly is inherently much safer to use. Along these lines, something you should pay attention to is the smoothness of a grinder as it runs. As an example, if you’ve ever used a cheap grinder, you’ve probably noticed how noisy they are and how much they vibrate. A good grinder doesn’t sound like it’s going to blow up, and is smooth and vibration free. Vibration will tire you out quickly and over the long term can damage your hands.



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What are you going to do with it?



First things first. Sounds simple enough, but some people may never use it for more than grinding paint. If that’s the case, your requirements won’t be the same as for someone that’s going to be beveling heavy wall stainless pipe for 12 hours a day, seven days a week. What I like to do is use different grinders, each set up for a different task. One with a cutoff/grinding wheel, one with a wire wheel, and one with a flap disc. I usually have one good grinder, and a couple of those cheap Chinese disposable grinders. I put the wire wheel and the flap disc on the junk Chinese grinders and put the grinding and cutoff wheels on my good grinder. This saves wear and tear on my good grinder, plus the junk grinders will work fine with the lighter loads of the wire wheel and flap disc. It also saves a lot of time switching wheels out.



What size Motor?



A grinder leads a tough life. It’s most always shrouded in smoke, dust, heat, and flying particles of red hot metal. Add to that the physical abuse most of them get, on a construction job site for instance, and it makes you wonder how they work at all.



The first thing to think about is that anytime that you can slow the wheel down when you’re using it, you’re pushing it past it’s maximum capacity. As you’re probably aware, it’s very easy to do this with most grinders. If you’re not sure how, put on a new grinding wheel and start pushing into the cut. You’ll notice right away that it’s very easy to get the grinder to bog down. Another way is to have an .040″ or .045″ cutoff wheel bind when you’re trying to cut something. Both of these are common occurrences, and can shorten the life of a grinder if done often.



A good analogy is that of an engine on a dynamometer. Maximum power happens at the point immediately before the engine can no longer keep up with the load. Once you start to slow it down, you’re past the maximum power. For grinders, this causes two problems - a higher current draw and lower cooling air flowing through the grinder. Two of the worst things you can do to any electric motor. Because of this, i always recommend buying a grinder that’s more than what you need. By oversizing, you’re effectively easing the burden on an already overworked tool, and in turn extending the service life you’ll get from it.



What size wheel?



I started using grinders way back in the early 80’s when Makita came out with what was then considered a somewhat revolutionary grinder. It was a 4″ grinder, and compared to a big, heavy, old black and decker 9″ grinders for instance, it was great. You could use it with one hand, and it was small enough so that you could get it in tight places. Another benefit was that it was extremely light and it didn’t wear you down after an hour of use. The main drawback, other than the first generation small diameter grinding and cutting wheels that had a tendency to explode, was that it had a 4″ wheel. You could literally burn up a wheel in seconds if you weren’t careful, or if you were too aggressive with the grinder.



Today they’re available in many different sizes; 4.5″, 5″, and 6″ (100mm,125mm, and 150mm in metric) being the common sizes. My personal favorite is the 6″. The first reason is that a 6″ wheel will last much longer than any of the smaller sizes. The jump from 5″ to 6″ makes a big difference in the life of the wheel. Also, for a given rpm, the larger wheel size will have a much faster rim velocity. This means it will cut or grind faster. Have you ever noticed that once your wheel starts to wear down it takes longer to cut or grind something? That’s because as the wheel wears down, the diameter of the wheel decreases, causing the rim speed and cutting/grinding speed to decrease. For these reasons, i suggest a 6″ or 150mm grinder. One thing to be aware of though is that in going with a larger wheel, you’ll need a grinder that can produce more torque. This translates into a higher powered grinder which also means a more expensive grinder. In grinders, like most everything else, you get what you pay for.






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If you work with metal, especially if you weld, there is one tool that is an absolute necessity. That tool is an angle grinder. They come in several different sizes, shapes, brands, and colors, but they all do basically the same thing-they spin some type of disc at a high rpm. The difference is how well
and how safely they do it. Before you buy a grinder, there are a few things that you should take into consideration when buying a small-(6″ or less), angle grinder. Some of the more important things are:

• What size motor (amperage)
• What are you going to do with it  
• What size wheel
• What features should it have
• Recommendations

A warning of sorts. A grinder is a very dangerous tool. An abrasive disc, or cut-off wheel spinning at 10000 rpms takes almost no time to slice through you. They can cut you to the bone, or worse, in the blink of an eye. Because of this, safety should be your first priority. One thing you should always do when operating a grinder is wear DOUBLE EYE PROTECTION - safety glasses or goggles AND a face shield. Even when I use both, there are times when I still get pieces of metal or grinding wheel in my eyes.



Also, make sure you have no exposed skin. Wear at the minimum long sleeve shirts. It’s even better to have a burn jacket or leathers. Flying pieces of red-hot metal and grinding wheel hurt when they embed themselves in you. Finally, always wear a minimum of leather gloves. I’ve accidentally touched or brushed my fingers against the wheel numerous times. When you use a grinder a lot, as some of us do, this happens. I hate to preach but you can’t slack off on safety when using a grinder. They’re dangerous and they’ll hurt you before you even know it.



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