Black & Decker Knife Sharpener, Sander, and File 3-in-1 Attachment

Why this 3‑in‑1 attachment earned a spot in my kit

Tight corners and awkward edges have a way of exposing the limits of palm sanders and detail blocks. That’s exactly where the Matrix 3‑in‑1 attachment shines. It’s a compact power‑file style detail sander with a built‑in knife sharpener, and it connects to a MATRIX power unit in seconds. I’ve used it for removing paint in window jambs, cleaning up the bottom edges of heavy furniture, and putting a quick working edge on utility and pocket knives. It’s not a replacement for a finish sander or a dedicated sharpening system, but as a problem‑solver for tight spaces and quick touch‑ups, it’s been genuinely useful.

Setup and compatibility

This attachment snaps into the MATRIX quick‑connect interface, so it goes from the toolbox to ready‑to‑use in about as much time as it takes to seat the collar. There’s no learning curve beyond getting used to the narrow sanding nose and the forward reach you get from the “power file” format. Note that you do need a compatible MATRIX power unit (sold separately); the attachment itself ships as a single piece without a motor.

Physically, it’s compact and easy to store—roughly 12.4 inches long, 6.5 inches high, and about 2.5 pounds. On a cordless MATRIX base, the balance felt neutral in my hands, and I could get a steady two‑handed grip for more precise control. Everything about it encourages you to get into places a typical mouse sander struggles with.

Detail sanding and power‑file performance

The slender, pointed nose is the star of the show. I used it to strip flaky paint out of inside corners on a door casing, where a triangular pad would have scuffed the adjacent face. With light pressure and a steady feed, it removed paint and old finish cleanly without digging. It’s particularly good along bottom edges—think toe‑kicks or the underside rim of a table where a round or square pad won’t fit.

On metal, I used it to knock rust off a garden bracket and to ease a sharp burr after a hacksaw cut. The narrow sanding path gives you control you don’t get with a wider belt or orbital pad. As with any power file, let the abrasive do the work. If you bear down, you’ll heat the work and burn through media faster.

A few technique notes that helped me:
- Keep the nose moving and approach corners at a slight angle to avoid gouging a single point.
- For paint or rust, make multiple light passes instead of one heavy pass.
- Use two hands—one at the base, one guiding the front—to track along edges.

It’s worth emphasizing this is a detail tool. It’s not efficient for flattening a large panel or sanding broad faces; you’ll spend a long time chasing stripes. But if your task is surgical—inside a notch, around hardware, along a rabbet—it’s in its element.

Knife sharpening: quick, functional edges

The integrated sharpener is a clever addition. It’s essentially a guided slot that lets the moving abrasive touch the edge at a consistent angle. I tried it on a kitchen utility knife, a folding pocket knife, and a fixed‑blade camping knife. In each case, I could bring a dull edge back to functional in a minute or two.

As with any powered abrasive on a knife edge, heat is the enemy. I made light, short passes, alternating sides, and wiped the blade between passes. The resulting edges were plenty for everyday cutting and field use. If you’re chasing mirror‑polished, hair‑popping edges on high‑end chef’s knives, a stone or guided system still has the final word. But for quick maintenance—especially on work knives that see cardboard, rope, and yard duty—the built‑in sharpener earns its keep.

Ergonomics and control

Because the motor and speed control live in the MATRIX base, the “feel” of the tool depends on the power unit you own. With my cordless base, trigger response was smooth enough to feather into corners. I do wish the base had a trigger lock for extended sanding; long sessions had my trigger hand doing more work than I’d like. That’s a limitation of the platform rather than this attachment, but it affects the overall experience on bigger jobs.

The attachment itself is easy to guide. The front end gives you line‑of‑sight to the contact area, and the slender profile makes it intuitive to track along an edge or into a recess. Vibration is noticeable—this is a narrow, fast‑moving abrasive path—but not fatiguing on short tasks. For extended use, I took breaks and swapped hands when possible.

Dust and cleanup

Expect minimal dust collection. Power files throw debris forward and off to the side, and this attachment is no exception. For paint and wood, I wore a mask and kept a vacuum handy to chase debris as I worked. On metal, safety glasses are non‑negotiable, and I like to set a rare‑earth magnet near the work to catch swarf. Cleanup is straightforward—blow the attachment out with low‑pressure air and brush the nose and guard area so grit doesn’t cake up.

Consumables and maintenance

A narrow abrasive belt or strip is doing the work here, and consumables go fast if you’re leaning on the tool. Plan on keeping a variety of grits on hand so you can remove material with a coarser media and finish with a finer touch. Changing media is quick once you’ve done it a couple of times, and keeping the contact area clean extends life and improves cut. Mechanically, there’s not much to fuss with—check that the belt tracks properly and that no debris is packing into the guide.

Where it fits in a workflow

The biggest advantage is workflow speed within the MATRIX ecosystem. I can drill pilot holes, switch to the impact attachment for screws, then snap on this 3‑in‑1 to clean up a proud edge or strip a paint puff from a tight corner—no dragging out a separate tool. For small shops and mobile work, the compact footprint is a real benefit.

Use cases where it stands out:
- Stripping paint and finish in inside corners, rabbets, and stopped grooves
- Easing sharp edges on metal brackets and trim
- Sanding the underside of shelves or the bottom edge of heavy furniture in place
- Touch‑up sharpening of utility, pocket, and field knives

Limitations

• It’s not a surface sander. Large, flat areas are better served by a random orbit or sheet sander.
• Dust control is limited; plan protective gear and cleanup.
• Edge discipline matters. The narrow nose can dig if you stop moving in one spot.
• The system requires a MATRIX base. If you’re not already invested, this attachment alone won’t do anything.
• Extended sanding sessions highlight the lack of a trigger lock on some MATRIX bases.

None of these are dealbreakers if you use the tool for what it’s designed to do, but they’re worth knowing before you buy.

Value and who it’s for

If you already own a MATRIX power unit, this attachment is a smart way to expand the system. It solves real problems that pop up in woodworking, home repair, and light fabrication, and it doubles as a practical knife maintenance tool. If you don’t own a MATRIX base, the math depends on how much you value the quick‑connect ecosystem and compact storage. A dedicated detail sander plus a separate sharpener could make sense for some users, but you’ll lose the convenience of one motor driving multiple tasks.

Homeowners tackling periodic projects, DIY woodworkers, apartment dwellers with limited storage, and tradespeople who want a compact detail solution in the van are the natural audience here.

Recommendation

I recommend the Matrix 3‑in‑1 attachment for anyone already in the MATRIX ecosystem who needs a precise, compact solution for detail sanding and occasional knife sharpening. It excels in tight, awkward spaces where broader sanders struggle, and the integrated sharpener is genuinely handy for keeping work knives in shape. You’ll want to manage expectations—this isn’t for flattening tabletops or producing chef‑grade edges—and accept that dust control is basic. But used as intended, it’s a capable, space‑saving attachment that meaningfully expands what your MATRIX base can do. If you’re not invested in the platform, weigh the convenience of quick‑change versatility against the cost of a separate base; otherwise, it’s an easy add to a small, efficient kit.