Black & Decker Replacement Auto Feed Spool

A small part that makes a big difference

Swapping line on a string trimmer is one of those chores that either keeps you productive or derails your yard work completely. After a season using the AF-100 spool across a couple of Black & Decker trimmers, I’m convinced this little prewound cartridge is the simplest way to keep light-duty trimming moving without fuss. It isn’t perfect—there are a few fit and feed caveats—but when it works as intended, it does exactly what you want: it disappears into the background and just feeds line.

What it is

The AF-100 spool is Black & Decker’s drop-in, auto-feed replacement for a broad swath of their corded and cordless trimmers. It comes prewound with standard 0.065-inch line and is sized to click into the round hub used on models like the GH600/GH900 corded units and cordless LST-series, LST136/LST300/LST400/LST420 among others. It’s sold individually (one spool in the bag), weighs almost nothing (about 0.1 lb), and is physically compact enough to stash a couple in the shed or mower bag.

The design philosophy is convenience: rather than hand-winding, you pop out the spent cartridge and snap in a fresh one. The trimmer’s AFS mechanism then meters out line automatically as it wears, with no bumping required.

Setup and installation

Installation is straightforward. On both a GH900 and an older LST136 I’ve used, it’s a two-step process:

• Press the tabs on the trimmer’s spool cap and remove it.
• Drop in the AF-100 spool with the line oriented in the direction indicated, feed the end through the eyelet, and reinstall the cap.

It takes under a minute once you’ve done it once. I did find that giving the hub a quick wipe to remove grass dust helps the spool seat cleanly. If the cap’s spring is gummed up, a quick clean there prevents drag on the auto-feed.

A small tip: pull 4–5 inches of line through the eyelet before replacing the cap, then trim to the guard’s line-cutting blade after the first spin-up. That prevents an initial snarl and lets the auto-feed index correctly.

In use: auto-feed that mostly stays out of the way

Auto-feed systems live or die by consistency. On both test trimmers, the AF-100 spool advanced line in small, predictable increments as I stopped and started at corners or edges. The feed rate matched light trimming and edging around beds, fence lines, and sidewalks. I didn’t have to bump the head, and I didn’t get the “foot of line all at once” problem that can shred a spool in minutes.

Cut quality in grass and typical lawn weeds is clean as long as you respect what 0.065-inch line is meant for. It trims edges, around sprinkler heads, and along a wooden privacy fence without drama. Dense, woody stems and tall, fibrous weeds do chew through line faster; that’s normal for this diameter. If you routinely attack overgrown lots or brushy perimeters, a thicker-line trimmer or a blade is the better call.

One behavior worth noting: Black & Decker’s AFS systems typically advance a little line each time you release and re-press the trigger. If you find you’re consuming line quickly, try to avoid rapid on-off cycles. Make a clean pass, then release the trigger when repositioning to reduce unnecessary feed.

Durability and line quality

Line longevity depends heavily on what you cut and how aggressive you are, but I was able to edge roughly 150–200 feet of sidewalk and trim fence lines across two sessions before needing to swap the cartridge on the GH900. On the LST136, which spins a bit faster under load, I got slightly less per spool when running high power. That’s in line with expectations for prewound 0.065-inch line.

The line on these cartridges resists welding (where wraps fuse together from heat), and I didn’t experience jammed layers mid-spool. Keeping the spool out of direct sun and, if you store spares, bagged with a bit of humidity helps maintain flexibility. If you ever do get a mid-spool hesitation, a quick removal and re-seat usually clears it.

The plastic spool body itself is sturdy enough to avoid deforming during installation. I didn’t notice burrs or flashing on the spools I used, which can matter for smooth feed.

Compatibility and fit notes

Fit is generally a non-issue on the listed compatible models, but tolerances matter. If your trimmer is older or the hub has seen sandy conditions, a tight fit can keep the spool from spinning freely, which stops auto-feed cold. A few practical checks that solved hiccups in my shop:

• Make sure the spool fully seats on the drive post; you should feel a positive sit, not a springy gap.
• Clean the inside of the hub and the underside of the cap; fine grit causes drag.
• Inspect the cap spring and the small cutting blade on the guard; damage there can mimic feed problems.
• If a new spool feels unusually tight on the center arbor, gently rotate it by hand before capping. If it still binds, exchange it—tolerance variation does happen.

If you’re mixing spools from different batches or aftermarket lookalikes, stick with the AF-100 designation for the models listed by Black & Decker. The AFS mechanism is sensitive to spool height and hub diameter.

Value and cost of ownership

At around $8.98 for a single cartridge, the AF-100 spool sits in the “pay for convenience” category. For occasional users or anyone who dreads hand-winding, the cost is justified by eliminating the most failure-prone part of trimmer maintenance. You’re paying to keep work moving.

If you trim weekly and burn through multiple spools per month, refilling an empty AF-100 spool with bulk 0.065-inch line can cut costs significantly, but it also reintroduces the potential for uneven winding and feed issues. My stance: keep prewound cartridges for quick swap-and-go, and refill the spent shells for less critical days. It’s a nice middle ground.

Who it’s for

• Homeowners with Black & Decker trimmers who want the least fiddly way to keep trimming.
• Light-duty yard work: edging, grass trimming, and typical lawn weeds.
• Users who share tools or manage a small tool fleet and value quick, repeatable setup.

Who should look elsewhere:

• Anyone frequently tackling woody brush or overgrown lots; you’ll want a thicker line or different platform.
• Users whose trimmer isn’t on the AF-100 compatibility list; confirm model numbers before you stock up.

Tips for better results

• Avoid rapid trigger cycling; it can feed extra line.
• Store spools in a cool, shaded place; a zip bag with a touch of humidity keeps line supple.
• Replace nicked or cracked spool caps; a worn cap can undermine auto-feed.
• If line snaps flush inside the head, remove the cap, pull 4–5 inches free, and let the guard blade trim it to length.

The bottom line

The AF-100 spool does what it promises: it keeps Black & Decker’s auto-feed trimmers running with minimal interruption. In my use, installation is quick, feed is consistent, and the line quality holds up for typical lawn care. While tolerance quirks can show up on some heads, a clean hub and a correctly seated spool have kept me working more often than troubleshooting. The price per cartridge isn’t cheap if you trim heavily, but the time saved—and the reduced frustration—are worth it for most homeowners.

Recommendation: I recommend the AF-100 spool for owners of compatible Black & Decker trimmers who value convenience and reliable auto-feed for light to moderate yard work. It’s an easy, low-friction way to keep trimming productive, with just enough durability to justify the cost. If you’re a heavy user, consider mixing prewound cartridges with occasional refills to balance convenience and budget.