Bosch 1-1/4 in. Starlock oscillating multi-tool bi-metal plunge cut blade

The short, sharp accessory I keep reaching for

A lot of oscillating tool blades promise to be do-it-all cutters, but few actually hold up across wood, nails, sheet metal, and plastics without turning into toast halfway through a job. After several weeks of mixed use—flooring adjustments, electrical box cut-ins, and a few “I wish I didn’t have to, but I do” nail encounters—the Bosch Starlock bi-metal plunge blade (1-1/4 in., model OSL114JF) has earned a consistent spot in my kit.

I used it on a Starlock-compatible multi-tool to undercut door jambs, trim shims and casing, notch plywood, slice out old copper stub-outs, and make plunge cuts in drywall and MDF. It isn’t flashy, and it doesn’t claim carbide-like immortality. It just cuts cleanly, seats securely, and lasts a sensible amount of time for a bi-metal blade.

Design and compatibility

The simplified 1-1/4-inch width is a sweet spot. It’s narrow enough for controlled plunge cuts between studs or in a crowded cabinet, yet wide enough to track straight and create mortise-like pockets. At roughly 1.5 inches of immersion depth, it has enough reach for most electrical box cut-ins, flooring undercuts, and hardware recesses. If you regularly need deeper pockets, you’ll bump this limit, but in day-to-day remodeling I rarely felt constrained.

The Starlock interface is the star here. The 3D cupped mount transfers torque efficiently and locks in with a positive, tool-free click. No loose screw, no occasional slippage under load, and changes take seconds. The flip side is obvious: you need a Starlock-compatible oscillating tool. If yours still uses a universal OIS clamp, this blade won’t fit.

Setup and handling

Out of the pack, the blade sits dead flat and true, with a flat-front profile that’s great for plunge work. I like that I can creep into a layout line with the corners and then open up the cut while keeping a steady sight line. The bi-metal tooth strip is fine enough to avoid ragged edges in pine and MDF, yet aggressive enough to bite into soft steel and copper without skating.

Balance on the tool is excellent. With the Starlock mount, vibration is as low as I’ve seen on an oscillating setup. That becomes obvious when you’re taking a long, steady notch in 3/4-inch plywood—the cut feels controlled rather than buzzy.

Cutting performance

• Wood and trim: In pine and poplar trim, the blade plunges predictably and tracks straight. Undercutting door jambs for flooring at a slight angle produced a neat, flat kerf with minimal tear-out. In plywood, it’s easy to keep a square shoulder if you let the blade’s corners score first and then advance.

• Wood with nails: Bi-metal is the right call for incidental nails and brads. I nicked several 18-gauge brads and one old finish nail during casing adjustments. The blade sparked briefly, kept cutting, and I saw only modest dulling along a few teeth. It’s not immortal—after several nail hits, cutting speed in hardwood slowed—but it never catastrophically lost teeth the way cheaper HCS blades often do.

• Metal: The blade handled copper and thin-gauge steel acceptably. Cutting 1/2-inch soft copper took a bit of oscillation speed and a light feed to avoid chatter, but the result was clean. In thin electrical box knockouts and sheet metal ducting, it made controlled openings without grabbing. For heavier or hardened fasteners, I’d step up to a carbide blade; this one is capable, not heroic.

• Plastics and drywall: In PVC the cut was fast and surprisingly clean with minimal melting at mid-range tool speed. Drywall cut-ins were quick with a narrow kerf that makes patching easier.

Accuracy and control

This blade’s biggest advantage is controllable plunge starts. The flat nose lets me “hinge” into a mark and maintain accuracy with minimal wandering. The modest width makes it easier to follow scribe lines on jambs or cabinet backs, and the tooth geometry leaves a clean shoulder if you’re excavating a shallow mortise for hardware.

The 1.5-inch immersion depth is honest. It’s sufficient for most remodel cuts, though you’ll need to plan two-sided attacks for anything thicker.

Durability and heat

Bi-metal construction buys you a real step up in life compared to high-carbon steel, especially with mixed-material cuts. Over a few small projects, I made dozens of plunge cuts in pine, MDF, and plywood, clipped several brads, and did light metal work. The blade still had life left—cut speed had dropped a bit in hardwoods, but teeth remained intact.

Heat management is decent. If you bear down in hardwood, you’ll see the usual oscillating-tool heat haze. Back off, lower the speed a notch, and add a slight oscillating motion to clear chips, and the blade rewards you with longer life. Compared to carbide, it will dull sooner on abrasive materials, but it also costs less per piece.

Practical tips from use

• Let the corners score your line, then pivot the body in—this reduces wander and tear-out.
• Use medium speed on plastics to avoid melting; high speed on wood; moderate on metals with light pressure.
• Clear chips frequently on deep plunges to keep the cut cool and fast.
• If you expect to hit multiple fasteners or hardened screws, switch to a carbide blade to preserve this one.

Value and pack options

You can get the blade as a single, in a 3-pack, or in a 10-pack. I started with a single to evaluate it, then moved to a multi-pack for jobs where metal encounters were likely. The per-blade cost in the larger packs makes sense if you’re on a remodel or demo where mixed materials are a given. It’s not the cheapest option, but the performance-to-cost ratio is favorable given the durability bump over basic HCS blades.

Limitations

• Depth: About 1.5 inches of immersion won’t suit deeper pockets or thick timbers without attacking from both sides.
• Metal extremes: It will handle incidental nails and thin steel, but it’s not the right blade for hardened screws, lag bolts, or repeated steel-only cutting—use carbide for that.
• Compatibility: Starlock-only. If your tool doesn’t have the Starlock interface, you’ll need a different blade or an upgrade.

Who it’s for

• Remodelers and trim carpenters who need reliable plunge cuts in wood and occasional nail encounters.
• DIYers who want a single blade to handle most tasks around the house: jamb undercuts, drywall cut-ins, PVC trimming, and light metal work.
• Anyone invested in Starlock tools who cares about quick, secure blade changes and consistent torque transfer.

If your work leans heavily into metal, or you’re frequently cutting screws and hardened fasteners, start with a carbide tooth blade instead and reserve this bi-metal for mixed-material days.

The bottom line

The Bosch Starlock bi-metal plunge blade hits that practical middle ground: fast, accurate plunge cuts, solid tooth life across mixed materials, and rock-steady mounting on Starlock tools. It doesn’t pretend to be a demolition specialist, and it doesn’t need to be. For the bread-and-butter tasks—jamb undercuts, outlet cut-ins, trim adjustments, and the inevitable brad or two—it’s a dependable, repeatable performer.

Recommendation: I recommend this blade for anyone with a Starlock oscillating tool who needs a versatile, durable option for plunge cuts across wood, plastics, and occasional thin metal. It offers a good balance of cut quality, control, and lifespan, and the multi-pack options make it cost-effective for ongoing remodel work. If your workload skews toward frequent, heavy metal cutting or hardened fasteners, pair it with a carbide blade and keep this one as your everyday cutter.