DeWalt 20V MAX* Brushless Cordless 4-1/2 in. Slide-Switch Grinder Kit

Why I reached for this grinder

On small metal jobs where dragging out an extension cord feels like overkill, I’ve been leaning on DeWalt’s 20V brushless 4-1/2 in. grinder. It’s a compact, slide‑switch model that promises 9,000 RPM and a bit more smarts than older tools thanks to its E‑Clutch and Kickback Brake. I ran it through the usual shop tasks—trimming rebar and bolts, grinding welds, cutting angle, and cleaning up rust with a flap disc—to see how it stacks up as an all-around cordless grinder.

What’s in the kit and first impressions

The kit is straightforward and useful: the grinder, a 5.0Ah 20V MAX battery, charger, side handle, inner and outer flanges, a clip‑on guard for cutting, a Type B guard for grinding, a hex wrench, and a soft bag. The bag holds the essentials and a handful of wheels, though it’s not as protective as a hard case.

Fit and finish are what I expect from DeWalt in this class—no flex in the gear case, crisp guard detents, and a cleanly finished slide switch. The bare tool is listed at 3.55 lb; with the 5Ah pack installed, it’s not featherweight, but the balance is good. I can one‑hand it for short cuts, and two‑handed grinding with the side handle feels planted without being fatiguing over longer sessions.

Ergonomics and controls

• Slide switch: This is a true slide‑to‑lock setup for sustained grinding. If you prefer a paddle trigger for maximum control during starts and stops, that’s a personal preference call. For me, the slide switch is great on long grind passes and less ideal for delicate cut starts on thin stock.
• Grip and balance: The head size is compact, so I can choke up near the guard for control. With the 5Ah pack, the tool balances slightly rear‑heavy in a way that keeps the disc light on the workpiece—nice for finishing with flap discs.
• Guard system: The grinder ships with a Type B guard for grinding and a clip‑on cutting guard. Swapping between them is quick and secure. If you plan to run 5 in. wheels, match them to the appropriate guard size as a safety best practice.
• Mesh intake screens: These screens help keep metal fines out of the motor. I still blow the tool out at the end of the day, but it’s nice insurance in a spark-heavy environment.

Performance under load

This grinder is rated up to 850 MWO (manufacturer value) and 9,000 RPM no‑load. In practice, here’s how that translated for me:

• Cutting: With a standard 4-1/2 in. bonded cutoff wheel, the tool held speed well through 1/2 in. rebar and 3/16 in. angle. It’s not a corded 13‑amp animal, but I didn’t experience meaningful bogging as long as I let the wheel do the work. Cross‑section cuts on rebar were smooth; long rips in angle iron took a bit more patience, as expected for a compact cordless grinder.
• Grinding: With a 1/4 in. grinding wheel, I could lean in at a moderate pressure without triggering protection. The brushless motor’s torque curve feels predictable; there’s enough headroom to clean welds and bevel edges without constant feathering.
• Finishing: A 60‑ or 80‑grit flap disc ran clean and vibration was well controlled. The motor’s ability to maintain speed made it easy to avoid gouging.

The brushless motor is the star here. Compared with older brushed 20V grinders, this one holds RPM more stubbornly and runs cooler, especially on longer grinding sessions.

Safety systems that actually add value

Two electronic aids help keep this tool in the “confident” column:

• E‑Clutch (anti‑rotation): When the wheel starts to bind in a cut or catches an edge during grinding, the clutch cuts power quickly. I intentionally pinched a cutoff wheel in tube steel to see how it behaved—the clutch tripped fast enough to prevent the classic wrist‑twist.
• Kickback Brake: In a more aggressive pinch, the brake stops the wheel quickly. It’s not there for dramatic marketing; it’s a practical safety layer that reduces the chance of an out‑of‑control wheel if something goes sideways.

These features aren’t excuses to get sloppy, but they do make the tool more forgiving when working in awkward positions or cutting unknown material.

Battery life and charging

DeWalt’s claim for runtime is up to 56 cuts of 1/2 in. rebar on a 5Ah pack (with a specific cutting wheel). My real‑world use was more mixed—some cutting, some grinding, some finishing. On a fresh 5Ah battery I was able to knock out a small steel‑fence repair (trimming eight pieces of rebar, grinding and fitting brackets, and cleaning welds) without reaching for a second pack. If you’re planning continuous heavy grinding, a second battery is still the right move.

The included charger topped the pack in roughly an hour in my shop. That’s quick enough that one battery can support intermittent work, but pros will want a spare on the charger for uninterrupted pacing.

Disc changes, flanges, and the “wrench” question

The grinder includes inner and outer flanges and a hex wrench. The outer flange on my unit has wrench flats, and the hex works for tightening/loosening. If you’re used to a traditional two‑pin spanner nut, note that this setup is different. My workflow preference is a quick‑change nut or a standard spanner to minimize over‑tightening; both are compatible if you’d rather swap the hardware. The spindle lock button is robust and easy to reach, and I didn’t encounter any cross‑threading or sticking.

Dust, durability, and maintenance

Grinding and cutting steel throws abrasive dust at every intake. The mesh screens help, and I noticed less buildup around the motor vents than I typically do on open‑vent designs. I still recommend blowing the tool out at the end of the day and avoiding extended grinding with the intakes directly in the spark stream.

The guards feel stout, the gear case runs smoothly, and there’s no odd gear lash noise. After a few weeks of regular use, I don’t see excessive wear on the flanges or switch.

What could be better

• Slide switch only: If you live on a paddle trigger for its inherent safety and control, you won’t convert here. This is a slide‑switch grinder aimed at sustained grinding comfort.
• Accessory hardware: The included hex‑based arrangement works, but a two‑pin spanner or quick‑change nut would be faster. I swapped to my preferred nut for day‑to‑day use.
• Soft bag: It’s fine for transport, but offers minimal protection. A hard case would better protect guards and wheels bouncing around in a truck.

None of these are deal‑breakers, but they’re relevant to how you’ll set up the tool.

Who it’s for

• Pros and serious DIYers who need a reliable cordless grinder for everyday cutting and grinding of steel in the 4–5 in. wheel range.
• Fabricators who want electronic safety protection without giving up the compact 4-1/2 in. footprint.
• Anyone already on DeWalt’s 20V MAX platform looking for a capable brushless grinder with a useful kit battery.

If you’re doing heavy stock removal all day, a higher‑power corded grinder (or a high‑output 18/20V grinder designed for 6 in. wheels) will still move material faster. But for most shop and site tasks, this tool hits a sweet spot of power, control, and runtime.

The bottom line

This DeWalt 20V grinder is a well‑balanced, capable cordless tool with real safety features, solid runtime on a 5Ah battery, and a guard system that makes switching between grinding and cutting straightforward. The brushless motor maintains speed better than older models, and the E‑Clutch/Kickback Brake combination earns its keep when a cut pinches or a wheel grabs.

I recommend it. It’s a practical, confidence‑building grinder for day‑to‑day metal work, especially if you value a slide switch for sustained grinding and you’re already invested in DeWalt batteries. Swap to your preferred wheel nut if you want quicker disc changes, keep a second 5Ah pack on hand for continuous work, and you’ll have a dependable cordless grinder that covers the majority of 4‑1/2 in. tasks without a cord.