Handheld angle grinders have traditionally been popular for metal working, but smaller diameter models are gaining wide use among masons, painters, and woodworkers. The variety of wheels you can equip them with -- wire, wire cup, stone, sanding, flapper, and diamond masonry-joint blades -- gives them great versatility.
Predictable results depend on choosing the right type of abrasive wheel. For example, a coarse stone quickly removes almost any material and is good for working on steel, but is overkill for cleaning up masonry. A lighter-impact, less-likely-to-clog wire wheel or cup would be a better choice. Sanding disks and wire wheels are much better than stone wheels for prepping surfaces for painting. Equipped with sanding disks or flapper wheels, angle grinders can also sharpen shovels, axes, scrapers, and wrecking bars.
We used nine 4-1/2-inch angle grinders to grind slag and rust from steel, paint and debris from wood and concrete, clean out mortar joints for tuck pointing, and cut concrete block down to size. We evaluated the tools' power, vibration, and overall ease of use; we also checked out adjustments, wheel changes, and balance. We tested the Bosch 1710A, Craftsman Professional 277421, DeWalt DW402K, Hilti HG-450, Hitachi G12S2, Makita 9564CV, Metabo WPS 7-115 Quick, Milwaukee 6154-20, and the Porter-Cable 7406.
Balance. With few exceptions, all the units we tested are more than adequate for any type of grinding small-diameter tools can perform. Quality showed her pretty face in balance and overall feel during use; these are critical elements, because grinder operations usually last a long time. As tough as they are, grinders also require a good "touch" -- more pressure for tough materials like slag and less pressure for flimsy stuff like paint.
When you're talking about balance, size matters. Longer units like those from Bosch, Metabo, and Porter-Cable are easier to hold in a wide range of positions and their added length makes them easier to manipulate in the materials we used. Shorter units like the Hilti, DeWalt, and Hitachi tools walked off the work in our wood, steel, and concrete trials. Their short bodies are also so thick that they're tiring to hold for extended periods of time. They also lack the longer tools' leverage.
The Bosch and Metabo tools are perfectly balanced, which made them easy to handle in all kinds of materials and positions. The Milwaukee grinder, the longest one by 2 inches, spread out the grip a bit too far, which made it cumbersome.
Vibration. When we used a coarse grinding wheel to grind slag off steel, all the units gave off some vibration. The Hitachi and Craftsman grinders rattled us the most, which reduced the amount of time we could use them comfortably. The Hitachi tool's smaller size and wider body diameter caused the excess vibration. The Craftsman grinder could use a better insulated body or grip to help smooth it out. The Bosch and Metabo tools were the smoothest operators of the bunch.
Switches. Grinders come with either paddle switches or on/off buttons. I like paddle switches, because the switch automatically fits in your hand when you pick up the tool. You just engage it; you don't have to try to find it with your thumb as you do with an on/off button. And, assuming I don't have the switch locked on, if the tool gets away from me and I let go of the switch, it'll just shut off instead of running until I unplug it.
Since I wear gloves when running a grinder, I like a huge, tactile switch. Again, a paddle switch fills the bill. The Bosch, DeWalt, Metabo, Milwaukee, and Porter-Cable tools all have paddle switches. Milwaukee's is simplest to use, followed by Bosch and Metabo, although they all worked fine.
It's not that on/off buttons don't work; in fact, some tool designers think they're safer to use than paddle switches if you grab the tool without checking to see if it's plugged in. And I even like Hitachi's center-mounted button, which lets you use the tool right- or left-handed with equal ease. But for my buck, paddle switches are easier to locate and quicker to turn on and off.
Wheel change. All the angle grinders we tested have spindle-lock buttons on the top/front of the units that make it easy to change the abrasive wheels. Metabo's is the largest and easiest to use, even with gloves on. The DeWalt and Porter-Cable buttons are small and difficult to manipulate with or without gloves on. The rest function pretty well.
Wire wheels and cups simply thread onto a grinder's spindle shaft, but you need special manufacturer-supplied wrenches to change most tools' abrasive wheels. However, Metabo's "Quick" clamping nut secures and removes the abrasive wheel without tools. It makes wheel changes quick and easy, even with gloves on. We'd like to see this feature on other tools.
Side handle. All the tools tested have removable side handles that thread onto the units' right or left sides. Some manufacturers' handles project 90 degrees from the unit. The handles on the Bosch, Hilti, Hitachi, Makita, Metabo, and Porter-Cable tools are angled about 70 degrees slightly forward. We like the latter position better; it's better when using the tools for long stretches.
The DeWalt, Milwaukee, and Porter-Cable models also have threaded holes in their tops for mounting the handles. This is particularly nice for tuck pointing or using a cut-off wheel; the handle is more in line with your natural stance and hand position, giving you a comfortable grip and a better view of the work surface.
Guards. Effective guards deflect sparks and dust and are easy to adjust. Most of the grinders' guards require set-screws to tighten them fully. Guards on these models loosened up and moved around on us during use, so we re-tightened them with an Allen wrench or screwdriver. The Bosch, Makita, and Milwaukee units have easy-to-grab, positive guard-locking systems that held the guards still throughout the test. They're tool-less, too.
Steel. We set the grinders loose on the edges of a freshly-cut piece of 3/8-inch steel plate to see how they handled slag. All the tools showed ample power. A coarse stone designed for metal work quickly removed unwanted material, but, left grinding swirls on the surface. We removed these with a finer grit stone; all the tools left a good finish and operated smoothly.
Surface prep. Next, we used a wire wheel to remove paint from wood, rust from steel plates, and to clean up concrete forms. The variable-speed Makita and Milwaukee tools came out ahead here. Controlling the wheel speed gave us better tool control and a better finished product, meaning fewer swirl marks.
The Bosch and Metabo units weren't far behind. Even at higher rpms, their superior balance and smooth operation are on par with the tool control the variable-speed units gave us. If the Bosch and Metabo tools had variable-speed motors, they'd be even tougher to match than they already are.
Tuck pointing. We put diamond cutter wheels on each model for cleaning up masonry joints, tuck pointing, and cutting concrete block. This is a tough job for a small grinder, and the Craftsman, Hilti, and Hitachi units met their match here. All the other tools powered through the mortar joints, cleaning them out nicely and turning anything they touched into a cloud of dust without bogging down.
We found units with top handle positions easier and more comfortable to control in this application. The same was true for cutting block. We had no power problems here, though; all the tools sailed through the block. Of course, they created enormous dust clouds as they went, which made me wish I had the Bosch and Metabo tuck-pointing attachments, which you attach to your vacuum. (We didn't test these accessories during this Tool Test.)
Exhaust. Because angle grinders run at such high rpms, they suck in and discharge a lot of air to stay cool. The units we like best pull in air from the rear and discharge it straight forward. The DeWalt, Milwaukee, and Porter-Cable models draw air from the side/rear and discharge to the front/sides, which didn't work well for us. The discharged air hit the side handle and deflected up into our faces. We liked the front-exhausting Bosch, Craftsman, Hilti, Hitachi, Makita, and Metabo tools much better.
All these tools work well, but some are better balanced, more powerful, and generally better to use. The Bosch tool was our favorite because its great balance, smooth operation, and well-routed exhaust made it handle flawlessly in any material we threw at it. Metabo came in a very close second for the same reasons. From there, the field finished as follows: Milwaukee, DeWalt, Porter-Cable, Makita, Hitachi, Hilti, and Craftsman.
Don Geary is a freelance construction writer who lives in Baker, Nev.
TOOLS OF THE TRADE has arranged with the companies in this test to donate their tools to Habitat for Humanity.