Black & Decker 3-in-1 String Trimmer/Edger & Lawn Mower

Why a compact 3‑in‑1 made sense in my yard

My small, chopped‑up lawn is a maze of narrow strips, raised beds, and a steep side yard that makes a conventional mower feel like overkill. That’s where the Black & Decker 3‑in‑1 (model MTE912) clicked for me: one tool that trims, edges, and, when snapped into a wheeled deck, mows the patches a full‑size machine struggles to reach. It’s corded, runs a 6.5‑amp motor, and spins a 12‑inch cutting swath. On paper that sounds modest; in practice, it’s a smart match for tight spaces and regular maintenance.

Setup and first impressions

Assembly is straightforward once you know what you’re looking at, but I’ll admit the first encounter with the pictogram‑heavy manual didn’t help much. The trimmer body drops into the mower deck and locks with a plastic latch; mine took a very firm push before it finally clicked. After that first snap‑in, removals and reattachments were smooth.

A few early notes that will save you time:
- You’ll need a two‑prong outdoor extension cord. The tool’s socket is recessed; bulky female ends don’t fit well. A slim, weather‑rated 14‑ or 16‑gauge cord worked best for me.
- The deck offers multiple cutting heights, but the icons aren’t intuitive. Pinch both wheel adjusters and move them together to keep the deck level.
- The auxiliary handle has multiple positions. Take a minute to dial this in; it makes a big difference in comfort.

Weight is reasonable at 14.2 lb with the deck on and noticeably lighter when used as a stand‑alone trimmer. I carried it up steps and into a terraced area without feeling like I was wrestling a machine.

Trimmer and edger performance

As a trimmer, the 3‑in‑1 is nimble. The head orientation locks for edging, and flipping between modes is quick. The 0.065‑inch line and automatic feed spool (AFS) do the heavy lifting. I had consistent line length without bumping—no downtime fiddling with the spool mid‑pass. The 6.5‑amp motor has enough torque to chew through typical lawn grass and the kind of broadleaf weeds that populate neglected fence lines. In very thick, wet growth, I learned to feather the trigger and take shorter bites; the gear‑drive helps resist bogging, but technique matters.

Edging is where this tool earns its keep in a small yard. With the string vertical, I got a crisp separation along the driveway and path edges after a couple of slow, steady passes. It won’t give you the hard‑edged look of a steel‑blade edger in compacted soil, but for weekly touch‑ups it’s surprisingly tidy.

Mower deck performance

Snap the trimmer into the 12‑inch deck and you get a lightweight string‑mower. Cut quality favors consistency over speed: it excels at regular trims but expects you to keep up with growth. On my mixed lawn (fescue, clover, and “whatever grows by the raised beds”), a single pass left an even finish at moderate heights. In taller patches, I made overlapping passes and lifted the deck one notch to avoid scalping, then dropped it for a second pass. Because there’s no side discharge, clippings stay contained beneath the deck and settle as fine mulch. I didn’t see debris shooting out from under the skirt, which I appreciated in tight spaces near windows.

Where you’ll hit the limits is in large, open lawns or thick St. Augustine‑type turf. The 12‑inch path simply takes longer, and trying to take off more than a third of the grass height in one go slows progress. Used as intended—for small lawns, townhome strips, courtyards, and hard‑to‑reach areas—it’s efficient and less fatiguing than muscling a full mower.

Ergonomics and handling

The rotating, multi‑position auxiliary handle is well‑placed and keeps wrist angles neutral in both trimmer and mower modes. Height adjustability is adequate for me at 5'10"; very tall users may wish for a longer shaft. The overall balance is front‑light, which helps with precise edging and keeping the deck level across uneven pavers.

Noise is comparable to a typical corded trimmer—far quieter than gas, louder than most battery units. Vibration is minimal, and after a 40‑minute session I didn’t feel hand fatigue.

Power, noise, and line feed

The 6.5‑amp motor paired with a gear‑drive transmission is the right combination for this format. I could push into moderately dense grass without the motor hunting or the head stalling. The AFS system is the unsung hero: it advances line automatically to maintain cut diameter. I used maybe a third of the included spool over two full yard sessions that included mowing, trimming, and edging. Keep an extra AF‑100/AF100LA compatible spool on hand; running out mid‑job is avoidable and swapping spools is quick.

Cord management and extension cord advice

Corded tools live or die by cord management. A few tips that made the 3‑in‑1 frictionless:
- Use a bright‑colored, lightweight outdoor cord with a slim female end to fit the recessed socket.
- Loop the cord through the handle’s relief to prevent accidental unplugging.
- Mow or trim moving away from your outlet so the cord stays behind you.
- For stairs or decks, drape the cord over a railing to keep it off your feet.

If you truly hate cords, this won’t change your mind. If you value uninterrupted runtime and have a compact yard, the tradeoff makes sense.

Maintenance and storage

Maintenance is minimal: brush the deck clean after use (unplug first), and occasionally cut away wrapped fibers near the head. The deck doesn’t pack with clippings the way a steel mower can, but damp grasses cling; a stiff nylon brush or a quick blast of air clears it.

Spool changes are simple—pop the cap, drop in a new spool, and feed the line through the eyelet. Stick with the recommended line diameter; thicker line can stress the motor and disrupt the AFS.

Storage is excellent. The deck detaches, and the trimmer hangs on a wall hook. The deck stands vertically against a garage wall and doesn’t hog floor space.

What could be better

No tool is perfect, and a few areas could use refinement:
- Instructions: The manual’s small, black‑and‑white images make assembly and deck height changes harder than they need to be. A QR code to a short setup video would solve this.
- First‑time deck latch: Mine required significant force to seat the trimmer into the deck the first time. It loosens with use, but the initial push is unnerving.
- Height range: Taller users may want a longer shaft adjustment.
- Recessed socket: Great for retention, but picky about cord ends. A slightly larger opening or included pigtail would help.
- Pace in heavy growth: It will do it, but plan on multiple passes and patience if you let the lawn get away from you.

Who it’s for (and who it’s not)

This 3‑in‑1 shines if you:
- Maintain a small to medium‑small yard, townhome strip, or courtyard.
- Need a lightweight tool you can carry up steps or maneuver around beds.
- Prefer corded reliability and don’t want battery management.
- Want one tool that covers mowing small areas, trimming, and edging without storage bloat.

It’s not ideal if you:
- Regularly cut large, open lawns where a wider deck saves hours.
- Expect vacuum‑clean bagging or a manicured, striped finish.
- Strongly dislike managing a cord.
- Need a long‑reach shaft for a very tall operator.

Final recommendation

I recommend the Black & Decker 3‑in‑1 for homeowners with compact, segmented yards who value flexibility and low effort. The 6.5‑amp motor, auto feed spool, and 12‑inch deck make quick work of weekly maintenance, especially where a full‑size mower is awkward or overkill. It’s easy to store, light to carry, and genuinely useful in all three modes. You trade some speed and sophistication—especially on large lawns and tall growth—for convenience and maneuverability. If that matches your yard and your expectations, this tool earns a spot in the shed.