• An angle grinder probably isn't the first cordless tool you'll buy, but one of the current models can make a useful addition to a tradesman's off-the-grid arsenal. Like 18-volt recip saws and rotary hammers, these grinders won't come close to replacing a corded version for all-day use, but most of them proved capable enough to have around for average jobs or for whenever the ease and convenience of cordless grinding and cutting is preferred.

    As a way to lower users' expectations, some manufacturers used to refer to their cordless tools as cut-off tools, instead of grinders. However, the evolution of technology, with better motors and batteries, have made the latest models good enough to be called grinders by every brand. A few are still best suited for light-duty work, but to my surprise, most of these tools are real go-getters, capable of making the sparks fly during rigorous grinding work … for a short while at least.

    I chose the kit form of the grinders (with batteries, charger, and case) where I had the option. All are available a la carte as add-on tools, but some are sold only that way.

    To determine each tool's mettle on metal, I made countless cuts and ground away lots of steel. I chose grade 40, #4 rebar for the competitive trials. Rebar, besides being a familiar material to builders and remodelers, is made very uniformly to government specs. The carbon steel is tougher than mild steels used in general fabrication work.

    To keep things even, I used identical 4 1/2-inch cut-off and grinding wheels from Norton in all of the grinders, even though some of the tools will fit 5-inch wheels.

    The tools also spent time in a professional welding and fabrication shop in the skilled hands of grinding maestros; craftsmen who wield an angle grinder with the ease and grace of a conductor's baton. These guys gave me great feedback regarding the finesse and ergonomics of these grinders. When fabricators need to remove a lot of metal in the shop, they typically grab a larger grinder, but smaller models like the ones in the test spend much of the day in their hands, blending and finishing surfaces before and after each weld they make.

    Grinder Uses

    The average building contractor may not spend the day with an angle grinder in hand, but for many uses, they are arguably the best tool for the job. Besides the obvious metal cutting and grinding uses, there are other tasks for which a grinder could be your go-to tool.

    Any time you have to cut or smooth metal against concrete or masonry, a disposable abrasive wheel has a real edge over toothed cutting blades that can easily be dulled or damaged. Cutting off misplaced rebar or anchor bolts flush to a foundation wall or grinding the stubs of concrete-form ties are good jobs for small grinders on site. For masonry itself, smoothing ridges left on concrete walls from form seams, demoing tile walls—backerboard and all—or slicing through plaster or stucco without ripping out the expanded metal lath are all great uses. In addition, during remodeling jobs, a grinder fitted with a thin cut-off wheel may be the smoothest way to cut neatly through mudded-in corner bead without tearing it from the drywall.

    Features

    At minimum, each grinder comes with a side handle, adjustable guard, and wheel attachment wrench, but some of the tools include a few extra accessories. Every brand has a switch circuit that protects the user against accidental startup. If you put the battery in with the switch turned on, the tool won't run until the switch is turned off first, then turned back on.

    Despite the relative simplicity of angle grinders, there are beneficial features that stood out during the testing:

    Grinder guards that do not require tools to attach or reposition are the key to efficient guard-adjusting.

  • Each tool comes with an open-bottom (Type 27) grinder guard, but models that also include an enclosed-bottom (Type 1) cut-off-wheel guard add to their utility and safety while cutting.
  • All of the tools have spindle lock buttons that let you tighten wheels with just one wrench, and a few of the tools have tool-free options for removing and even attaching wheels.
  • Grinders with lock-on switches allow more freedom of movement and create less fatigue than those with a paddle switch or trigger that must be held on.
  • The grinders that fit 5-inch wheels allow you to use longer-lasting cut-off wheels, however, the extra torque required for grinding with a larger wheel may sap the tool's strength.
  • Grinders with motor brakes increase productivity because you can set the tool down immediately after use, instead of waiting for the wheel to stop.
  • While it was hard to detect the exact benefit in use, two of the top models feature high-tech brushless motors with electronic instead of brushed commutation designed for high-efficiency operation.

 Number of cuts through 1/2-inch rebar on a fully charged battery. Tested with Norton RightCut Type 1 cut-off wheels, .040-inch thick.
Number of cuts through 1/2-inch rebar on a fully charged battery. Tested with Norton RightCut Type 1 cut-off wheels, .040-inch thick.

 Grams of steel removed per minute during two, 2-minute trials of heavy grinding on a fully charged battery. Tested on rebar with Norton Gemini Type 27 grinding wheels. A corded model was included as a point of reference.
Grams of steel removed per minute during two, 2-minute trials of heavy grinding on a fully charged battery. Tested on rebar with Norton Gemini Type 27 grinding wheels. A corded model was included as a point of reference.

 Time in seconds to make 10 cuts non-stop through 1/2-inch rebar on a fully charged battery. Tested with Norton RightCut Type 1 cut-off wheels, .040-inch thick.
Time in seconds to make 10 cuts non-stop through 1/2-inch rebar on a fully charged battery. Tested with Norton RightCut Type 1 cut-off wheels, .040-inch thick.

Bosch CAG180-01

Battery: 18 volts, 4.0 Ah
Battery gauge: 3 bars, on battery
Weight: 5.1 pounds
RPM: 10,000
Switch type: lock-on slider switch
Guard: 4 1/2-inch grinder guard, 4 1/2-inch cut-off wheel guard
Guard adjustment: requires hex wrench (stored onboard tool)
Web price: kit $399; bare tool $125
Includes: tool, 2 batteries, charger, cut-off guard, wheel wrench, fabric duffel bag
Country of origin: tool: Germany; battery: Malaysia

Comments: Solid third-place tool with great runtime and a light, agile form, but it slows under load more than the top two.
Pros: Separate grinder and cut-off guards; small switch positioned to the side keeps it well out of the way; slender body easy to grip.
Cons: A hex wrench is required to adjust the guard, which slows down the process.

DeWalt DCG412M2

Battery: 18 volts, 4.0 Ah
Battery gauge: 3 bars, on battery
Weight: 6.3 pounds
RPM: 7,000
Switch type: trigger
Guard: 5-inch grinder guard, 5-inch cutoff wheel guard
Guard adjustment: tool free
Web price: kit $299; bare tool $119
Includes: tool, 2 batteries, charger, cut-off guard, wrench, fabric duffel bag
Country of origin: tool: Mexico; battery: Japan

Comments: A strong tool that gets extra torque from its slower motor, but its bulky rear handle with a trigger is not preferred over a standard grinder design.
Pros: Separate grinder and cut-off guards; 5-inch guards lets tool fit wider range of wheels.
Cons: Biggest and heaviest; bulky handle design; having to hold on to trigger adds fatigue and diminishes grip versatility; grip with handle way at the back makes it cumbersome, especially when following curves.

Hilti AG 500-A18

Battery: 21.6 volts, 3.3 Ah
Battery gauge: 4 bars, on battery
Weight: 6.1 pounds
RPM: 9,500
Switch type: paddle switch
Guard: 5-inch grinder guard, plastic cover for cut-off use
Guard adjustment: tool free
Other features: tool-free wheel nut; brushless motor, metric M14 shaft
Web price: kit $559; bare tool $329 (manufacturer's list price)
Includes: tool, 2 batteries, charger, cut-off guard cover, wrench, 25 cut-off wheels, fabric duffel bag
Country of origin: tool: China; battery: China

Comments: This fast cutter shares third place, but it's at its best when applied in short intervals; when pushed hard for very long its speed wavers under load.
Pros: Fast motor brake; cut-off guard cover plate snaps onto grinder guard without tools; 5-inch guard let tool fit wider range of wheels; nice wrench-free wheel nut can save time
Cons: Once motor speed dipped under load, it took a while with the pressure let up before the brushless motor found the top of its range again; this characteristic seemed to slow output more noticeably during longer periods of use; paddle switch only—would prefer a sliding switch.

Hitachi G18DSL P4

Battery: 18 volts, 3.0 Ah
Battery gauge: 2 bars, on tool
Weight: 5.0 pounds
RPM: 9,100
Switch type: lock-on slider switch
Guard: 4 1/2-inch grinder guard
Guard adjustment: requires screwdriver (not included)
Web price: bare tool $90
Includes: tool, wrench
Country of origin: tool: China; battery: China

Comments: Light-duty tool with only modest power and runtime; outclassed by other tools in the test but its compact form was appreciated for lighter finishing work.
Pros: Light weight, good balance, and lots of rubber grip surfaces made this downsized tool a standout for one-handed finishing work.
Cons: Limited to light work; screwdriver is required to adjust the guard which slows down the process; unlike the others with multiple LEDs on the battery, has a more rudimentary fuel gauge with two LEDs on the tool itself; lacks cut-off guard.

Metabo WP18LTX115

Battery: 18 volts, 5.2 Ah
Battery gauge: 4 bars, on battery
Weight: 5.5 pounds
RPM:8,000
Switch type: paddle switch (lock-on slider switch model also available)
Guard: 4 1/2-inch grinder guard
Guard adjustment: tool free
Other features: rotating battery, removable filter screen, overload warning light
Web price: kit $399; bare tool $103.
Includes: tool, 2 batteries, charger, wrench, plastic case
Country of origin: tool: China; battery: Hungary

Comments: Firsts in every test really says it all; hands-down the best tool for serious cutting and grinding with powerful and predictable performance.
Pros: Unique rotating battery lets you optimize the tool's form and balance for different grinding and cutting positions; filter screen a nice extra for protecting the motor.
Cons: Would rather have the sliding-switch version (W18LTX115) rather than the paddle-switch version for ease of use; lacks cut-off guard.

Milwaukee Fuel M18 Brushless

Battery: 18 volts, 4.0 Ah
Battery gauge: 4 bars, on battery
Weight: 6.0 pounds
RPM: 8,500
Switch type: lock-on slider switch (paddle switch model also available)
Guard: 5-inch grinder guard, 5-inch cut-off wheel guard
Guard adjustment: tool free
Other features: rubber bushing in handle, removable filter screen, brushless motor
Web price: kit $399; bare tool $169.
Includes: tool, 2 batteries, charger, cutoff guard, wrench, spare filter, plastic case
Country of origin: tool: China; battery: Korea and China

Comments: Strong, smooth second-place tool. A real comfort standout. Comes with useful accessories and extras.
Pros: Fast motor brake; separate grinder and cut-off guards; 5-inch guards let tool fit wide range of wheels; rubber bushings on front handle and slender, rubber-covered rear handle provide a great feel in use; wheel nut can be removed without a wrench; filter screen protects motor.
Cons: Extra length can reduce maneuverability in some uses.

Ridgid R86040B

Battery: 18 volts, 4.0 Ah
Battery gauge: 4 bars, on battery
Weight: 5.5 pounds
RPM: 9,000
Switch type: lock-on slider switch
Guard: 4 1/2-inch grinder guard
Guard adjustment: tool free
Other features: overload warning light on tool, three-position handle
Web price: bare tool $99
Includes: tool, wrench
Country of origin: tool: China; battery: China

Comments: Light-duty tool that stalls quickly and frequently under load due to its overprotective battery feedback circuit. This characteristic makes it frustrating to use and limits the tool to timid grinding and cutting uses only.
Pros: Balanced compact tool, but heavy.
Cons: Hair-trigger protective circuit shuts off tool before user feels or hears it slow; two distracting LEDs on tool caution the user to ease up, but they go on almost constantly; the limited amount of pressure you can apply to stay below the warning threshold is much less than with the other tools; lacks cut-off guard.

The Bottom Line

Once the flying sparks had bounced their last, the grinding swarf had all settled, and the hot steel had cooled, I had to admit that I was quite impressed by the performance of these 18-volt cordless angle grinders. Of course, like many cordless tools, the minutes of actual runtime under a decent load can be counted on one hand, but when you consider that equals about 45 cuts through #4 rebar, it's a respectable amount of work. All of the tools could do the light grinding of finishing work such as smoothing welds and putting a radius on sharp corners, but when pushed harder, the more powerful tools proved their worth for serious grinding and cutting.

The Metabo takes the top spot, as it won every single power, speed, and runtime test. It also has advanced features. In the No. 2 spot is the Milwaukee, with a great combination of power when it counts the most and many advanced features. Great performances by Bosch and Hilti have them sharing third, and the powerful yet clumsy DeWalt follows. The light-duty Hitachi was a comfort standout, especially for finish work, but is really not in the same class as the more powerful tools above. The Ridgid trailed behind all with its timid output, doomed by a load limiter set too far below the level of work a cordless grinder needs to do.

Thanks to Norton Abrasives for the grinding and cut-off wheels used for the test and to the guys at Longmont Welding, in Longmont, Colo., for their contributions.

Test Results

During testing, materials to be cut and ground were secured in a vise and supported along their length to minimize vibration. Identical new 4 1/2 inch cutting or grinding wheels were installed on each tool prior to each test.

Runtime

Number of cuts through 1/2-inch rebar on a fully charged battery. Tested with Norton RightCut Type 1 cut-off wheels, .040-inch thick.

Grinding Speed

Grams of steel removed per minute during two, 2-minute trials of heavy grinding on a fully charged battery. Tested on rebar with Norton Gemini Type 27 grinding wheels. A corded model was included as a point of reference.

Cutting Speed

Time in seconds to make 10 cuts non-stop through 1/2-inch rebar on a fully charged battery. Tested with Norton RightCut Type 1 cut-off wheels, .040-inch thick.