Bosch Starlock Oscillating Multi-Tool Carbide Grit Plunge Cut Blade

Why I reached for this blade

I keep a few specialized oscillating-tool blades in the kit for jobs that wreck normal bi-metal teeth. Grout, thinset, plaster with sand, fiber cement—those are abrasive materials that turn standard blades into butter knives. The Bosch carbide-grit plunge blade has become my default for those tasks. It’s a 1-1/4 in wide, 1.5 in immersion-depth, carbide RIFF edge on a Starlock mount, and it’s purpose-built for grinding its way through materials that don’t care about teeth.

Setup and mounting

I ran the blade on two tools: a Starlock-compatible oscillating multi-tool and a popular OIS-style tool with a universal clamp. On a Starlock tool, the connection is as slick as advertised: line it up, press, and you’re cutting in seconds. The three-dimensional mount locks positively and noticeably reduces slop at the interface—there’s a crispness to the cut feel you don’t get with flat-flange mounts. On the OIS-style tool, it’s still straightforward to mount and plenty secure, but you lose the true one-handed, snap-on convenience.

The blade is made in Switzerland and the build quality shows. The body is stiff, the brazing on the carbide grit is even, and the Starlock stamping is clean with no burrs.

Cutting performance on abrasive materials

• Grout removal: In kitchen and bath grout, the blade chews steadily rather than bites. That’s exactly what you want—controlled erosion of the joint without grabbing. Using a medium oscillation speed, I could clear standard grout lines quickly, keeping the blade slightly angled so the grit rides the grout and not the tile edges. On sanded grout, progress is brisk; on epoxy-modified grout, it still works, but slower.

• Mortar and thinset: For rework around a shower curb and a floor transition, the blade ground out thinset and skim-coat cleanly, letting me plunge in, outline, and peel the surface back. It’s effective for creating shallow channels for cable or sensor wire runs—just remember the 1.5 in depth limit.

• Concrete and expansion joint fillers: On cured sealant and crumbly filler, the blade doesn’t complain. In harder, aggregate-rich areas, it keeps going, but expect slower progress and more heat. Let the grit do the work; leaning on it only makes dust and heat without improving speed.

• Fiber cement and plaster: In cement board and plaster with sand, the blade remains controllable and predictable. The plunge profile is handy for cutouts around boxes where a segmented blade might skate.

It’s worth stressing: this is a grinding blade, not a toothed cutter. If you try to “saw,” you’ll get chatter and heat. Glide, don’t shove.

Control, accuracy, and plunge cuts

At 1-1/4 in width, the blade feels nimble in tight spaces while still covering ground on linear runs. The plunge tip is easy to steer, and the 1.5 in immersion depth is enough for grout, thinset, plaster, and most patch work. For deep channels in concrete or brick, you’ll reach the depth limit. In those cases I score with this blade, then break out material and repeat the pass.

The Starlock interface helps with control. With less backlash at the mount, the tip tracks where I aim it, especially at higher oscillation speeds. Vibration is well controlled compared to flat-mount blades, which makes it easier to keep a feather touch near delicate surfaces.

Tile edges and delicate surfaces

If you’re clearing grout next to fragile or glossy tile, use restraint. The carbide grains will happily kiss a tile glaze and leave a scar. Two habits help:
- Keep the blade slightly angled so the grit concentrates in the joint.
- Reduce speed as you approach the last bit near the tile edge, and let the edge of the grit just polish the remaining grout away.

Blue tape on tile faces gives a visual buffer, and a steady hand beats brute force every time.

Durability and lifespan

Carbide grit wears predictably: performance starts strong and tapers as the grains break down. In grout and thinset, I can get through a sizable area before the cut rate noticeably slows. In concrete or cementitious fillers with angular aggregate, wear accelerates. Eventually you’ll grind the grit down flush with the blade body, and cutting slows dramatically.

A few tips to extend life:
- Run mid to high oscillation speed but keep pressure light—let grit and speed do the work.
- Use short, oscillating sweeps to keep the edge cool.
- Vacuum dust as you go; packed dust insulates and creates heat.
- If one side slows, flip the tool orientation to use fresh sections of the edge.

The steel body holds up well. I’ve seen minor glazing and the expected polish on the grit but no delamination or shedding under normal use.

Dust and heat management

This blade turns a lot of abrasive material into fine dust. A vacuum close to the work is not optional indoors—it’s necessary. I typically pair the tool with a small nozzle held to the cut line and wear a P100 respirator in enclosed spaces. If dust starts to cake the grit, a quick brush with a stiff nylon detailing brush brings the cutting back.

Heat is the other reality. If you notice the blade coloring or smell hot binder, back off and let it cool. Short passes and patience keep the edge sharper longer.

Compatibility and fit

The Starlock mount is the star here. On a Starlock tool, blade swaps are truly seconds and the torque transfer feels more immediate. On OIS-compatible tools with a lever clamp, fit is still good, though not quite as “locked in.” The blade’s geometry doesn’t interfere with common tool clamps and guards. If your workflow involves a lot of swapping between metal and abrasive cuts, Starlock’s speed is a real advantage.

Where it shines and where it doesn’t

Shines:
- Removing grout without hammering the surrounding tile or substrate
- Cutting and shaping thinset, mortar, and plaster with sand
- Scoring or channeling in cement board and similar composites
- Cleaning out expansion joint fillers and surface contaminants on concrete

Doesn’t:
- Cutting wood cleanly—this is not a finishing blade
- Cutting metal—carbide grit is wrong for that job
- Deep trenching in concrete—the 1.5 in depth and heat buildup limit you

Value

It’s not a bargain-bin accessory, and you feel that on the receipt. The counterpoint is efficiency and control. If you charge for your time, the speed and precision in abrasive materials justify the cost. For occasional DIY grout touch-ups, one blade will likely outlast the project. For heavy concrete work, plan on consumable wear and budget for replacements.

Small details that matter

• The 1-1/4 in width is a sweet spot: narrow enough for accuracy, wide enough for productivity.
• The plunge profile helps establish clean start lines without exterior scoring.
• Being Swiss-made isn’t marketing fluff here; the consistency of the grit and brazing translates to predictable performance.
• Pack quantity is one; if you’re starting a large job, have a spare on hand to keep momentum.

Recommendation

I recommend the Bosch carbide-grit plunge blade for anyone who regularly faces abrasive materials—tile installers, remodelers, maintenance techs, or serious DIYers tackling grout and thinset. It combines precise control, genuinely reduced vibration on Starlock tools, and a durable carbide edge that holds up well in the materials it’s designed for. The quick-change Starlock interface is a real workflow upgrade if your tool supports it, and compatibility with OIS-style mounts keeps it flexible across brands.

It’s not a do-everything blade, and it’s not cheap. But used correctly—light pressure, steady speed, good dust control—it’s fast, predictable, and safer around delicate finishes than more aggressive alternatives. For grout removal, shaping cementitious layers, and light concrete cleanup, it earns its place in the kit.