Bosch 3-1/2 In. Starlock Oscillating Multi Tool High-Carbon Steel Segmented Saw Blade

What I used it for

I put Bosch’s 3-1/2-in segmented high-carbon steel blade to work on a handful of real jobs: undercutting door jambs for a floating floor, trimming casing for tile transitions, flush-cutting dowels and shims, and making straight relief cuts in plywood where a circular saw couldn’t reach. I ran it primarily on a Starlock-compatible multi-tool, and I also tried it on an older OIS-style tool with an adapter to check fit and feel.

In short, this is a purpose-built wood and plastic blade that rewards proper use with clean, controlled cuts. It’s not a do-everything accessory—and it shouldn’t be mistaken for a metal-capable or demolition blade—but for general carpentry tasks the performance is consistently solid.

Mounting and compatibility

The Starlock interface is the star here. It snaps on without a screw, it’s rigid under load, and it transmits torque without the slop I still feel from slotted, bolt-on blades. Being able to index the blade at multiple angles makes awkward flush cuts—tight to baseboard or along flooring—much easier to set up.

On my Starlock tool the connection is flawless. On an OIS tool, I used a simple adapter; the blade sat a hair off square on that particular setup but didn’t affect cut quality. The usual caveat applies: if your oscillating tool predates Starlock or uses a proprietary clamp, you may need an adapter or a different arbor. Check compatibility before you buy.

Build and design

This is a segmented, 3-1/2-in “half-moon” blade with an HCS cutting edge and a published immersion depth of 1.5 in. The body feels noticeably stout compared to bargain blades. The listed 0.125-in thickness reads as overbuilt for an oscillating accessory, and in use that extra stiffness shows up as reduced chatter and better tracking in long cuts. You trade a bit of speed and a little more heat generation for that stability, which I’ll take for finish work.

Laser-etched markings make it easy to identify in a crowded blade box, and Bosch’s color cue around the interface is actually useful on the job—grab the wood blade without squinting. The etching held up after dusty cuts, which I can’t say for most painted-on labels.

Cutting performance in wood

• Door jambs and casing: With the blade indexed parallel to the floor and a scrap of the new flooring as a gauge, undercutting jambs went quickly and cleanly. The segmented edge lets you tack along a straight line against a guide; there’s no nose to “catch” on entry like a straight plunge blade can. I found it easiest to keep oscillation speed high and feed lightly—let the teeth work and the blade doesn’t burn, even on oak.

• Flush trimming: Cutting hardwood dowels and wedges flush to stock was simple. Because the blade is stiff, it doesn’t flex and gouge adjacent surfaces as easily. A bit of painter’s tape on either side of the cut served as insurance and left me with minimal sanding.

• Plywood and MDF: Cross-grain cuts in veneered plywood were better than average for an HCS half-moon—some fuzzing on the exit side, but no tearing of the face veneer when I scored the line first with a utility knife. In MDF and primed finger-joint casing, the edge stayed clean over several meters of cutting.

• Engineered flooring: The aluminum-oxide finish on many engineered planks can be murder on cheap teeth. This blade held up through a handful of transitions and a few notch cuts without obvious dulling. Again, lighter pressure keeps heat down and extends life.

Where this blade does not shine is anywhere near metal. Wickedly embedded finish nails in trim will dull HCS quickly. If you expect to encounter fasteners, switch to a bi-metal or carbide blade.

Precision and control

Oscillating tools are inherently approachable, but they can skate in hard material. The Starlock interface, combined with the blade’s stiffness, noticeably improves control. I could track a pencil line along baseboard without the blade wandering, and because the edge is segmented, you can use a guide block or the workpiece face itself to steer a straight path.

The max immersion depth of 1.5 in is enough for most trim and flooring tasks, though it won’t replace a saw for deeper cuts. Inside corners are a limitation: a half-moon can’t finish a tight interior corner, so I kept a straight plunge blade handy to square those up.

Heat, vibration, and noise

With any HCS oscillating blade, heat is the enemy. I found a few habits made a clear difference:

• Let the tool do the work; don’t pry.
• Use higher oscillation speed and a lighter feed.
• Back the blade out periodically on long cuts to clear dust.

Do that and you’ll avoid scorch marks on hardwoods, you’ll keep the edge sharper longer, and the tool feels smoother in hand. On both tools I tried, vibration was lower than with thinner, no-name half-moons—less chatter, less rattling feedback in awkward cuts.

Durability and value

In wood and PVC, longevity is good. I put the blade through multiple rooms of jamb undercuts, trimmed several feet of casing, and made a dozen or so plywood notches before I felt the cut slow down. At that point, a quick touch with a brass brush to clear resin helped, but as with all HCS, once the edge is dull it’s time to replace.

It’s not the cheapest single blade you’ll find. You’re paying for the Starlock interface, a stiff plate, and Swiss-made consistency. If you push it into metal or construction debris, you’ll burn that value quickly; if you keep it on wood and plastic, the cost-per-cut lands in the fair-to-good range for pro and serious DIY use.

Where it fits in a kit

Use this blade when you need:

• Clean, controlled straight or flush cuts in wood and plastics.
• Long, guided cuts along a surface (baseboard, jambs, flooring).
• A rigid accessory that won’t deflect easily under side load.

Reach for something else when you need:

• Metal cutting or wood with unknown fasteners (bi‑metal or carbide).
• Tight plunge starts in small openings (narrow, straight plunge blade).
• Dead-square inside corners (finish with a straight blade or chisel).

Tips for best results

• Score veneer before cutting to reduce fuzzing.
• Tape your cut line on prefinished trim to protect surfaces.
• Use a sacrificial spacer (like your flooring offcut) to set jamb undercut height.
• Feather the feed; if you see smoke, you’re pushing too hard or the teeth are dull.
• Keep a brass brush in the pouch to clear pitch and keep the teeth biting.

The bottom line

The Bosch 3-1/2-in segmented HCS blade earns its keep in the wood and finish work lane. The Starlock mount is fast and rock-solid, the blade tracks straight, and the stiffness translates into cleaner, more predictable cuts. It’s not a demolition blade and it’s not meant for metal; treat it like a finishing tool for wood and plastics and it will return clean results and respectable life.

Recommendation: I recommend this blade for anyone with a Starlock multi-tool who does trim, flooring, cabinetry installs, or general carpentry and wants a dependable, clean-cutting half-moon for wood. It’s especially worthwhile if you value quick, secure blade changes and consistent cut quality. If your work routinely encounters hidden fasteners or involves metal, choose a bi-metal or carbide blade instead; otherwise, this Swiss-made HCS segmented blade is a smart, reliable addition to the kit.