Bosch 3-1/2 in. Starlock Bi‑Metal Flush Cut Blade

What it is and where it shines

Bosch’s Starlock bi‑metal blade has become one of my default oscillating attachments for jobsite cleanup and punch‑list work. It’s a 3‑1/2 in. segmented, flush‑cut blade with a bi‑metal edge and a Starlock three‑dimensional mount. That combination tells you a lot about its intent: broad, controlled cuts; good durability across mixed materials; and a mount that transfers torque without the chatter you sometimes get on flat OIS tabs.

In practice, the blade’s width makes it ideal for straight, guided cuts—trimming shims proud of jambs, undercutting small sections of casing, or nibbling back drywall and PVC. The bi‑metal teeth handle wood with the stray nail, copper pipe, and typical construction fasteners without folding over at the first spark. It’s not a specialist’s carbide grinder, and it isn’t meant to be, but it covers a lot of day‑to‑day tasks well.

Mount and compatibility

The Starlock interface is the headline feature, and it matters. On a Starlock body, you get a positive, tool‑free snap‑in that genuinely tightens up the connection. That translates into less vibration and a more even stroke at higher speeds. I ran the blade primarily on a Bosch Starlock tool and also clamped it onto an older OIS‑style multi‑tool; in both cases it seated securely. If you’re mixing brands, this cross‑compatibility is a real advantage, especially in shops with a mix of legacy and newer tools.

Color coding on the hub and laser‑etched markings on the face are small touches that help in a crowded kit. Even after a few hot cuts, the etching stayed readable enough to identify the profile and material rating.

Build and design details

A few specs shape how this blade behaves:

• Width: 3.5 inches. That large face tracks straight and bridges gaps, which helps when you’re referencing off a floor or jamb for a flush cut.
• Thickness: 0.125 inch. This is on the stout side for an oscillating blade. The upside is rigidity—less deflection when you’re leaning into a cut. The trade‑off is a wider kerf and slightly slower progress in dense material.
• Segmented edge and limited immersion depth. This profile excels at flush and surface cuts; it’s not the choice for deep plunges. If you need to plunge more than a quarter inch, a narrower, straight‑plunge profile is better.

The bi‑metal edge is the right compromise for mixed‑material work. It outlasts high‑carbon steel in abrasive materials and won’t crumble the first time you graze a nail. It won’t match carbide on hardened fasteners, but that’s expected.

Performance in wood and drywall

My first use was trimming door shims and undercutting a few irregular drywall patches. Running at mid to high speed on a Starlock tool, the blade stayed planted with minimal jitter. The broad face works like a mini fence—press it flat, and it naturally tracks straight along the surface.

• Wood: In clean pine and poplar, the cut is predictable and splintering is low if you let the teeth do the work. Against hardwood casing, the blade remains controllable, though you’ll feel the thicker kerf. For precise finish cuts, score your line and keep the oscillation speed a notch below max.
• Drywall: It’s almost effortless. The blade’s stiffness keeps it from waving off line, and the segment profile gives you visibility around the cut.

One note: the 0.125 in. kerf is noticeable if you’re trying to preserve a tight reveal. If tight tolerances matter, make your line accordingly and don’t force the feed.

Cutting PVC and nonferrous metals

On PVC traps and electrical conduit, the blade sails through with a clean edge. The bi‑metal teeth shed chips rather than melting the plastic—provided you keep the speed controlled. For nonferrous metals, like soft copper and aluminum profiles, it’s a capable option for short, controlled cuts. Clamp the work, use modest pressure, and let the blade clear chips; that keeps the edge sharp longer.

Nails, staples, and the occasional screw

The “wood with nails” claim holds up. I purposely buried a few 16‑ga and 18‑ga brads in poplar and cross‑cut through them. You’ll see sparks, but the teeth survive and keep cutting. For bright framing nails, it remains practical.

Where bi‑metal reaches its limit is hardened fasteners and larger screws. It will cut the head off a drywall screw or a corroded #8, but the heat ramps quickly and tooth life drops if you stay in that lane. For a batch of screw extractions, a carbide edge is a better investment.

Vibration, control, and heat

This is where the Starlock mount earns its keep. Compared to flat‑tab blades clamped on a standard bolt, this interface reduces micro‑slip, which you feel as steadier cutting. Less chatter also means cleaner entry when you’re flush‑cutting against finished surfaces.

Heat management is decent for a bi‑metal. On repeated metal contacts, the blade gets hot—no surprise there. A quick cool‑down between cuts, or alternating back to wood/drywall tasks, extends life. If you try to bulldoze through continuous metal, you’ll shorten the edge life in a hurry.

Noise is typical for an oscillating blade; dust is manageable on drywall if you pair it with extraction. The wide face actually helps funnel dust forward where a nozzle can catch it.

Durability and value

Over several days of mixed tasks—wood trimming, a handful of nail encounters, about a foot of PVC, and some drywall—the blade retained a usable edge with predictable slowdown rather than sudden tooth loss. That’s what I expect from bi‑metal: a steady tapering of performance, not a cliff.

Is it the longest‑lasting option for metal? No. Carbide holds up longer in abrasive and metallic cuts. But as a generalist, the bi‑metal edge offers solid value, especially if most of your work is wood, drywall, and light metal contact instead of continuous metal cutting.

Limitations to keep in mind

• Limited plunge depth: The segmented profile is for surface and flush cuts, not deep slots. If you need to dive deep into a stud or notch a joist, pick a narrow plunge blade.
• Kerf width: The 1/8‑inch thickness adds stability but removes more material and can slow progress in hardwood.
• Heavy metal duty: Expect reasonable life with nails and brads; don’t expect it to chew through a pocket full of hardened screws without significant wear.

None of these are flaws so much as design choices. Choose the right blade for the job and this one performs as advertised.

Practical tips for best results

• Let the mount work for you: On a Starlock tool, snap in and pull straight cuts at higher speeds; the interface keeps vibration down.
• Don’t force it: Especially in metal, moderate pressure and a controlled speed keep teeth sharp longer.
• Score finish surfaces: For clean trim work, score first with a knife and start with a shallow pass.
• Manage heat: If you hit metal repeatedly, give the blade a breather or mist the cut lightly to keep temps down.
• Use the width as a guide: The 3.5 in. face is great for referencing off floors or walls to keep cuts square.

Who it’s for

If your day includes general remodeling tasks—trimming shims, undercutting casing, cutting back drywall, tackling PVC, and occasionally meeting a nail—this blade is a dependable, no‑drama choice. If you’re a maintenance tech or a residential remodeler carrying a single blade to cover 80% of what pops up, it fits the bill. Metal‑heavy work, demo of old lath with embedded screws, or frequent encounters with hardened fasteners call for stepping up to a carbide profile.

Recommendation

I recommend the Starlock bi‑metal blade as a reliable, general‑purpose flush‑cut accessory for oscillating tools. It combines a secure, low‑vibration mount with a stiff, wide profile that tracks straight, and a bi‑metal edge that survives everyday contact with nails and fasteners. It isn’t a deep‑plunge specialist and it won’t outlast carbide in metal, but for the work most of us do—wood, drywall, PVC, and the occasional fastener—it offers consistent performance, good control, and sensible durability. If you run a Starlock tool or a compatible OIS‑style multi‑tool and need a go‑to blade that just works, this one earns a spot in the kit.