AOBEN Cordless Angle Grinder 4-1/2 inch, 21V Battery Grinder Tool, Power Electric Grinders, Brushless Motor, 2x4.0Ah Battery & Charger, for Cutting, Grinding, Polishing

Why I reached for this cordless grinder

I keep a corded 4-1/2-inch grinder on a hook in the shop, but more and more I’ve been reaching for cordless when I’m working on vehicles, gates, or anything that’s not right next to an outlet. I picked up the Aoben grinder to see if a budget-friendly, brushless option with two batteries could keep pace with my regular workflow—cutting rusty fasteners, knocking down welds, cleaning mill scale, and dressing edges. After several weeks of metal work, some paver trimming, and a handful of flap-disc cleanup jobs, here’s how it fared.

Build, ergonomics, and first impressions

Out of the case, the tool feels compact and reasonably balanced with a battery installed. The rubber overmold and moderate neck diameter make it easy to control with gloved hands. The auxiliary handle threads in on either side for right- or left-handed work, and I found the angle and shape comfortable for longer grinding sessions. Fit and finish are what I expect in this price range: clean casting, snug guard fit, and a positive-feeling spindle lock.

The kit includes two wheel guards—a full guard and a half guard. The full guard is my go-to for grinding and flap discs, while the half guard offers better sightlines for cutting without flinging debris straight at your wrist. Swapping guards is quick, and the guards held position without drifting once tightened.

Everything rides in a hard plastic case with foam cutouts. It’s not compact, but it keeps the batteries, charger, discs, and grinder from rattling around. If you’re tossing tools in a truck bed, the case is a plus.

Controls and speed options

This grinder uses a brushless motor and has three selectable speed modes, with a top speed of 9,500 RPM. The speed selector is a simple push-button interface on the panel near the battery, and it’s easy enough to toggle even with gloves. There’s also good feathering available from the trigger, so you can creep into a cut or gently start a flap disc. In practice:

• Low speed was ideal for flap discs and light surface prep where I wanted more control and fewer sparks.
• Medium handled most rust removal, descaling, and edge cleanup without chattering.
• High was my choice for cutting and grinding down welds.

I like having speed presets on a grinder. It let me tame aggressive discs without hunting for a perfect trigger position, and it helps keep heat down on thin material.

Cutting and grinding performance

Power-wise, the Aoben grinder sits in the “strong enough” tier for general-purpose work. Cutting 1/8-inch mild steel with a thin cut-off wheel was smooth and predictable, and it tracked straight through threaded rod and exhaust tubing. On a handful of welds across 3/16-inch plate, the grinder kept pace with a 40-grit flap disc and a standard grinding wheel. If I leaned hard, I could bog it slightly—typical behavior for a cordless grinder outside of the top-tier pro models—but easing pressure kept it in the sweet spot.

Vibration is manageable, and the tool doesn’t ring your hands even during extended flap-disc work. Noise is what you’d expect from a 4-1/2-inch grinder; the brushless motor adds a higher-pitched whine at full speed, but nothing beyond the norm.

I tested a few tile cuts with a segmented diamond blade. At medium speed, the grinder was easier to control and kicked up less chipping on glazed ceramic. That adjustable top speed genuinely earns its keep for delicate materials.

Wheel changes and compatibility

The 5/8"-11 spindle and 7/8" arbor are standard, so all my existing 4-1/2-inch wheels fit. The spindle lock is easy to reach, and wheel swaps are straightforward with the included wrench. I prefer wheel nuts with thumb tabs, but that’s personal taste—no issues with the included setup.

As for the discs in the kit, they’re fine for getting started and testing the tool. For production work or critical cuts, switch to name-brand abrasives. Quality wheels last longer, run cooler, and cut straighter.

Battery life and charging

This kit includes two 21V 4.0Ah batteries and a charger. Runtime depends heavily on the task and wheel, but these are realistic expectations from my use:

• Heavy grinding on steel with a standard grinding wheel: around 10–15 minutes of continuous work per battery.
• Flap-disc cleanup and rust removal: 15–25 minutes, depending on pressure and speed setting.
• Thin cut-off wheels on mild steel: a dozen or so typical cuts per battery before performance tapers.

Swapping batteries kept me moving steadily through a day’s worth of small tasks. For extended grinding on thick steel, I plan around short breaks or use a corded grinder to complement this one. Charging from empty took roughly two hours per battery. Not fast, not painfully slow—average for this class.

The electronics include overload and thermal protection. I managed to trip it twice by burying the wheel in a bind. Each time, backing off and waiting a moment brought the grinder back to life. I prefer a conservative protection scheme to a smoked motor, and the brushless setup ran cooler than many brushed cordless grinders I’ve used.

Safety and control

With the full guard fitted and set correctly, spark control is good and easy to aim. The half guard is useful for long cuts where visibility matters, but I recommend a long-sleeve shirt and a face shield either way—this tool can throw a lot of material at high speed, especially with the top speed selected.

Trigger feel is predictable, and the brake time after releasing the trigger is typical for a grinder without an electronic brake; the wheel coasts for a moment. Plan your set-downs accordingly.

What stands out—and what doesn’t

Highlights:
- Brushless motor with three speed modes makes this grinder more versatile than single-speed budget options.
- Two batteries and a decent charger in the box mean you can work out of the case immediately.
- Ergonomics are solid: comfortable handle positions, good balance, and a control layout that doesn’t get in the way.
- Standard spindle and arbor play nicely with common wheels and accessories.

Trade-offs:
- The included discs are “starter kit” quality. They work, but upgrading abrasives noticeably improves performance and runtime.
- Charging isn’t fast; heavy users will want a third battery or a faster charger if available.
- It’s a standalone battery platform. If you’re already invested in a big-brand ecosystem, sharing packs across tools is a convenience you won’t get here.
- Under aggressive load, it can bog; let the wheel do the work and it performs well.

Use cases where it shines

I found the Aoben grinder especially handy for:
- Field work and garage tasks where dragging a cord is a pain.
- Rust removal, surface prep, and weld cleanup on light to medium steel.
- Occasional masonry or tile trimming at the mid speed setting with a diamond wheel.
- Projects that benefit from speed control, like flap-disc finishing on thin stock.

If you live on a grinder eight hours a day or routinely hog off heavy material, you’ll still want a corded model or a top-tier pro cordless running larger packs. For the kinds of jobs most homeowners, DIY fabricators, and maintenance folks do, this tool is capable and convenient.

The bottom line

The Aoben grinder delivers credible power, useful speed control, and practical runtime in a well-thought-out kit. It doesn’t replace a corded grinder for sustained, heavy grinding, and the included discs are strictly for getting started. But the brushless motor, two-battery setup, standard spindle, and dual guards make it a competent, flexible addition to a small shop or jobsite kit.

Recommendation: I recommend the Aoben grinder to DIYers and light-duty pros who want cord-free convenience without paying top-tier prices. It’s a solid performer for cutting, grinding, and surface prep, with speed control that genuinely improves handling and finish quality. If you’re already invested in another battery system or you need maximum power and runtime, look to a brand that matches your existing packs or step up to a corded grinder. For everyone else, this kit offers strong value and dependable performance.