DeWalt ATOMIC 20V MAX 4" Angle Grinder

Why a 4-inch cordless grinder still earns a place in my kit

Small grinders get underestimated. The first time I pulled the trigger on the Atomic 4-inch grinder, I understood what DeWalt was aiming for: a compact, high-speed cutter that slips into spaces where a 4-1/2-inch or 5-inch grinder won’t, without feeling underpowered. After a few weeks of cutting fasteners, trimming thin-gauge steel, and touching up mower blades, it’s clear this isn’t a “miniature” grinder so much as a purpose-built one.

Setup and first impressions

Out of the box, mine included the reversible flange set, a pin wrench, a Type B guard with a clip-on Type A guard, and two Type 1 cutting wheels (1/16 and 1/8 inch). The switch gear and guards are intuitive if you’ve used grinders before. The paddle switch has a positive lock-off that becomes second nature, and the spindle lock makes wheel swaps quick. The guard’s clip-on design is smarter than it looks—being able to convert between a Type B and a Type A configuration without extra hardware lets me match the guard to the task.

This is a bare tool, so you’ll need your own 20V MAX battery and charger. With a 5Ah pack installed, the balance sits slightly rear-biased but not tippy, and the slim grip makes it easy to index your hand, even with gloves.

Power and speed where it matters

On paper, the brushless motor is rated at 755 MWO and spins up to 12,500 RPM no-load. In practice, it’s snappy off the line and maintains speed well with thin cutting wheels, which is exactly where a 4-inch grinder excels. I used it to:

• Zip off shiner framing nails and protruding screws
• Cut 1/8-inch angle and light channel for brackets
• Flush-trim bolts and threaded rod
• Reshape and sharpen mower blades

With a 1/16-inch cutting wheel, I could lean into cuts on mild steel without bogging. On the mower blades, it was easy to hold a consistent angle, and the tool never felt like it was laboring. The smaller diameter does limit maximum cut depth, but it also means the wheel stays flatter and truer under load, which helps accuracy and reduces chatter in thin stock.

Electronic brake and anti-rotation safety

Two safety systems stand out. The electronic brake snaps the wheel to a stop in about a second after you release the paddle—fast enough to set the tool down confidently and avoid accidental scuffs or freewheeling near your work. The anti-rotation system is equally valuable: if the wheel pinches or binds, it instantly kills power. I deliberately induced a bind in a piece of angle iron, and the grinder cut out before the tool twisted in my hand. You do need to cycle the switch to restart, which is exactly what I want after a stall.

Combined with the no-lock-on paddle switch, it’s a conservative safety package that doesn’t get in the way of work.

Ergonomics, cooling, and control

The slim body is easy to wrap your hand around, and the paddle switch falls naturally under the fingers. Because the tool is short and light for a grinder, it’s easy to maneuver in awkward orientations—inside stud bays, up against joists, or around brackets where a bigger grinder’s guard would bump. The forward exhaust is subtle but noticeable; instead of hot air and dust blowing back into your hand or face, the airflow pushes forward. That’s not a substitute for PPE, but it does make prolonged use a little more comfortable and keeps grit off your wrist.

Vibration is well controlled for a high-speed compact grinder. Using quality wheels, I had no issues with tingling hands after a longer session cutting rod and small bar stock.

Guards and accessory compatibility

Guard flexibility is a highlight. The default Type B guard is what I used for most general tasks. When I swapped to the clip-on Type A guard for certain cutoffs, I appreciated the extra clearance and visibility. The swap is straightforward—no screws to drop, no hunting for an extra bracket.

A few notes on accessory fit:

• It’s a 4-inch grinder. It does not accept 4-1/2-inch or 5-inch wheels. Plan your cuts with the smaller diameter in mind.
• The reversible flange accepts 4" x 3/8" and 4" x 5/8" non-hubbed accessories. That flexibility helps when sourcing discs.
• Because 4-inch wheels aren’t as ubiquitous in some stores as 4-1/2-inch, I keep a small stock on hand. Thin kerf cutoffs, a couple of grinding discs, and a flap wheel cover most of my needs.

The spindle lock is firm and well shielded, and the included pin wrench worked with the flange nut without drama.

Runtime and batteries

Runtime on grinders is always a dance between battery capacity and workload. On a fresh 5Ah pack, I knocked out a punch list of nail and screw cutoffs, then moved to trimming angle and still had juice to spare. Continuous heavy grinding will drain any battery-powered grinder quickly, but this one feels particularly efficient when paired with thin cutting wheels—likely the sweet spot for the high-RPM, small-diameter setup.

If you plan on using it as a daily driver for metalwork, budget for at least two 5Ah packs or a single high-capacity pack, and let the tool cool between deep cuts. The brushless motor recovers quickly, and the forward exhaust helps keep heat from lingering around your hand.

Where the 4-inch size shines (and where it doesn’t)

The strengths of the Atomic 4-inch grinder are tied to its compact format:

• Tight spaces, flush cuts, and overhead work where a bigger guard gets in the way
• Cleaner control in thin-gauge material, sheet, and small-diameter stock
• Fast, precise cutoff work with thin wheels at high RPM

Trade-offs are equally clear:

• Shallower cut depth versus 4-1/2-inch or 5-inch grinders
• Smaller selection of wheels in some regions—plan purchases accordingly
• No lock-on switch, which some users prefer for long grinding sessions

If your work frequently includes deep cuts in thick bar or plate, a larger grinder will simply be faster and more versatile. I view this as a specialist that covers 80% of my on-site or maintenance cutting with less bulk and more finesse.

Durability and serviceability

The build feels robust. The guard detents still bite cleanly after multiple adjustments, and the paddle switch hasn’t loosened up. The gearbox remains tight with no odd play. Being TOOL CONNECT chip ready is a nice nod to fleet users—installing a chip to track runtime and location is simple, but you do have to buy the chip separately. DeWalt’s warranty (3-year limited, 1-year service, 90-day satisfaction) is standard fare and appropriate for a pro-leaning tool.

Everyday usability

A few practical notes from daily use:

• The switching logic after a stall (cycle to restart) prevents accidental spin-ups if you’re still pinched in a cut.
• The brake speeds up task flow more than you might expect—you spend less time waiting for the wheel to wind down.
• The smaller disc means fewer sparks and better sightlines in some positions, which helps when you’re cutting near finished surfaces.

Wear your PPE—eye, hearing, and gloves—and be mindful that this is still a 12,500 RPM tool. Respect the guard and wheel ratings.

The bottom line

The Atomic 4-inch grinder is a compact, high-speed cutter with excellent safety features and surprising power for its size. It won’t replace a 4-1/2-inch or 5-inch grinder for deep cuts or heavy grinding, but it excels at the tasks most people actually perform with a cordless grinder: quick cutoffs, trimming, touch-ups, and work in tight spaces. The guard system, brake, and anti-rotation are well executed, and the ergonomics make it easy to control.

Recommendation: I recommend it if you value compact size, precise control, and a built-in safety suite for everyday cutting and light grinding. It’s an easy choice for punch-list work, maintenance, HVAC, electrical, and carpentry crews who already run 20V MAX batteries. If your projects demand frequent deep cuts or heavy stock removal, consider this a complementary tool alongside a larger grinder rather than your only grinder.