Bosch 1-1/4 In. Starlock Oscillating Multi Tool Hook Knife Blade

Why a hook blade belongs on your multi-tool

I reach for an oscillating multi-tool constantly, but not every task is a straight plunge or flush cut. For soft, fibrous, and layered materials, a dedicated hook knife blade is simply faster, cleaner, and safer. That’s exactly where Bosch’s hook knife blade shines. It’s a compact, 1-1/4-inch-wide cutter with a hooked profile, a high-carbon steel edge, and a Starlock mount. After putting it to work on carpet removal, heavy cardboard breakdown, and shingle trimming, it earned a permanent spot in my kit.

Setup and compatibility

As a Starlock accessory, the blade snaps onto Starlock tools with a positive, no-screw connection. The three-dimensional interface transfers torque more efficiently than OIS-style flat mounts, and it also keeps the blade locked without wiggle. I appreciate the quick, touch-free blade change—pop it on, pull it off—especially when I’m switching between this and a scraper or segmented blade.

If your multi-tool uses an OIS interface, this blade is listed as compatible with many popular brands through the appropriate adapter. I tested it on a Starlock multi-tool primarily, then verified fit on a second-brand OIS-style tool with an adapter without drama. The laser-etched markings and color-coding are practical touches when you’re rummaging through a box of accessories.

Blade design and what it’s for

The hook profile is the star. Rather than forcing a push cut, the curved edge grabs material and lets you pull steadily, which keeps the tool stable and reduces the chance of runaway gouges. The 1.5-inch immersion depth is enough for most flooring, underlayments, and roofing layers; the 1.25-inch width gives good visibility and control around corners or along baseboards.

High-carbon steel (HCS) is the right call for soft to medium materials. It’s sharp, fast, and inexpensive compared to bi-metal. The tradeoff, as with any HCS blade, is that it’s not designed for abrasive composites or metal. Avoid staples, tack strips, or roofing nails, and it will reward you with clean cuts.

Intended uses are spot on: carpet, cardboard, and asphalt shingles. I’d add foam underlayment, roofing felt, house wrap, and thin vinyl sheet goods to that list based on feel and cut quality, with the same caveat to avoid hitting metal.

Performance in the field

• Carpet and pad: This is where the blade pays for itself. I like to pull a lengthwise cut to section off manageable strips. The hook bites into the backing without skittering across fibers, and I can follow a chalk line along the room. Compared with a utility knife, I get less binding and far fewer stalls, especially on cushion-backed carpet. The oscillating action keeps the cut moving even when the blade path gets gummy with adhesive.

• Baseboard breakaways: When cutting carpet right against baseboards or around door casings, the narrow width and hook profile let me keep the tooth engaged while the body of the blade clears the trim. It’s more controlled than a straight-edge plunge blade and avoids scarring painted surfaces.

• Heavy cardboard and packaging: For breaking down double-wall boxes, I pull the hook toward me at a shallow angle. It tracks like a box-cutter but without the tip-catching issues. The oscillation means even flattened seams open up easily. It’s terrific for shop cleanup and recycling prep.

• Roofing shingles: On three-tab asphalt shingles and underlayment, the blade works well for shaping around vents and trimming overhangs. The hook keeps me in the cut, and the 1.5-inch reach handles layered edges. That said, shingles are abrasive; the edge does dull faster here than on carpet or cardboard. Cutting felt and house wrap is no problem and doesn’t noticeably affect the edge.

Vibration is modest with the Starlock mount; there’s less chatter than I typically feel with OIS blades tightened under a single center screw. On a variable-speed tool, mid-to-high speed tends to cut cleanly without heating up the edge prematurely.

Precision and control

The hook profile acts like a guard rail. Once the edge is engaged, it naturally follows your pull, so curves and inside cuts are easy to steer. I found scribing around a floor register straightforward: plunge the tip to start the lead-in, roll the hook to maintain contact, and let the oscillation do the work. Visibility is better than with wider “scraper-style” blades, and the Starlock’s rigid connection helps keep the cut line honest.

Durability and maintenance

HCS is sharp but not invincible. Here’s what I observed:

• On carpet and pad, one blade handled a full room of sectioning and perimeter trimming with a still-usable edge by the end. The cut quality tapered, but it didn’t require excessive force.
• On shingles, edge life fell off faster. Expect to clean the blade periodically—roofing granules and tar build up. A quick scrape and a wipe with a bit of mineral spirits kept it cutting.
• Any contact with staples or nails will leave a nick; once that happens, the cut gets ragged. It’s worth doing a pass with pliers or a scraper to expose and remove fasteners before cutting.

Because it’s a single-pack accessory, plan on a couple in the bag for larger demo or roofing days. At the same time, the precision manufacturing shows: the edge grind is consistent, the mount is tight, and the blade body stays flat.

Ergonomics and workflow

The utility of the Starlock mount goes beyond convenience. No-screw changes mean less downtime and no lost flange bolts. When I’m alternating between this hook blade for long pulls and a straight plunge blade for notching, the workflow feels seamless. Also, being able to orient the blade at different angles relative to the tool head helps with awkward corners and left/right-hand pulls.

Laser-etched identification is a small but appreciated detail when blades are dusty—no guessing which hook profile I’m grabbing. The color coding aligns with material categories, which is handy if you maintain a mixed drawer of accessories.

Tips for best results

• Use a shallow approach angle. Let the hook grab; don’t force a deep bite.
• Set a mid-to-high oscillation speed for carpet; slow slightly for felt and thin plastics to keep edges tidy.
• Map and remove staples or roofing nails before cutting. The blade will thank you.
• For long cuts, guide with your free hand pressing the material taut ahead of the blade to reduce bunching.
• Clean adhesive and tar buildup with a safe solvent to maintain cut speed. Avoid wire wheels that can round the edge.

Limitations

• Not for metal. Even light-gauge nails or staples will damage the edge.
• Shingles are doable, but they’ll consume the blade faster than carpet or cardboard.
• The 1.5-inch immersion depth covers most tasks, but thicker stacks may need a pass from both sides or a different accessory.

If you need one blade to attack nails, screws, dense composites, and fiber cement, this isn’t it. That’s not a flaw—just the reality of HCS and the task it’s designed for.

Where it fits in a kit

For flooring installers, remodelers, and anyone who does tear-outs, this blade fills the gap between a utility knife and a standard plunge blade. It turns the multi-tool into a controlled pull-cutter that’s safer in tight spaces and more efficient on fibrous materials. I keep it alongside a scraper, a bi-metal plunge, and a segment blade—those four cover 90% of my on-site accessory needs.

Recommendation

I recommend the Bosch hook knife blade for anyone using a multi-tool on carpet, packaging, roofing felt, and asphalt shingles. The Starlock mount is rock-solid and fast to change, the hook profile delivers controlled, clean pulls, and the HCS edge cuts quickly in the materials it’s designed for. Just respect its limits: avoid metal contact, have a spare for abrasive roofing work, and keep it clean. If those constraints match your workflow, this blade is a small investment that meaningfully improves both speed and cut quality on the jobs it’s built to handle.