Bosch Hex shank screw pilot bit set

Why I reached for this set

I reach for combo pilot/countersink bits whenever I’m hanging hardware, running trim, or assembling shop fixtures. The Bosch set has been riding in my drill pouch for a couple months now, covering the common wood screw sizes (#6, #8, #10, and #12) with a simple formula: a replaceable pilot bit paired with a two-flute countersink/counterbore and a 1/4-inch hex shank. On paper, it promises faster, cleaner screw installs in wood, plastics, and composite sheet goods. In practice, it largely delivers, with a few caveats worth knowing before you put it to work.

Design and build

Each bit is a one-step unit: a standard twist pilot leading a two-flute conical cutter fixed to an adjustable collar. The collar slides on the pilot and is locked with a small set screw using the included Allen wrench. That setup lets you tune both the depth of the countersink and the length of the pilot—useful when you’re moving between soft pine, dense hardwood, and man‑made boards.

• Shank: 1/4-inch hex. It snaps into quick-change chucks, holds steady in standard keyless chucks, and seats fine in a drill press chuck.
• Sizes: One bit each for #6, #8, #10, and #12 screws. Those four cover most furniture, jig, and general carpentry jobs.
• Flutes: Two flutes on the countersink. That’s a common geometry and, with the right feed and speed, it leaves a clean seat.
• Weight and bulk: At about 0.14 lbs for the set, they’re compact and unobtrusive in a pouch or drawer.

Machining on my set is tidy. The pilots run true enough for accurate hole placement, and the countersink edges are crisp. There’s no stop collar or spring-loaded depth control—just the sliding countersink body—so your repeatability depends on your setup and a steady trigger finger (or a drill press).

Setup and adjustment

There’s a minute of initial fiddling to dial each bit to your screws. Here’s what worked well for me:

1. Loosen the set screw and slide the countersink to expose enough pilot for your screw length. As a rule of thumb, I set the pilot length to roughly 60–70% of the screw’s threaded length in softwood, a touch less in hardwoods to preserve holding power.
2. Snug the set screw, then test on scrap. Start with a shallower countersink than you think you need; you can always deepen it. You want the screw head to finish flush or just a hair below the surface.
3. For counterboring (hiding the head under a cap or plug), slide the body a little farther and slow your feed rate. The two flutes can bore a shallow recess cleanly if you clear chips often.

The Allen screw holds securely if you actually tighten it, not just snug it. I haven’t had one slip mid-job, but I developed the habit of giving it a quick check when I swap sizes. Keep the tiny wrench with the set—there’s nothing worse than pausing to hunt for a 2 mm hex when you’re halfway through a run of hinge holes.

In wood: soft, hard, and sheet goods

This is where the Bosch set earns its keep. In Eastern white pine, I can run the drill at a medium-high speed and get crisp, chatter-free countersinks with minimal fuzz around the edge. The pilots evacuate chips well for their size; I rarely need to peck unless I’m drilling deep.

On denser woods like maple and oak, dropping the speed a notch helps. The two-flute cutter leaves a clean conical seat if you keep a steady feed. I got the best results by:

• Using a sacrificial backer when drilling through face frames to avoid blowout on the exit.
• Clearing chips between holes when counterboring deeper than a typical screw head depth.
• Waxing screws for long or large-diameter fasteners (#10 and #12) to reduce drive torque and prevent heat glazing the countersink.

Plywood and MDF are always a good test of a countersink’s manners. With decent support and moderate speed, the Bosch bits leave neat seats in cabinet-grade ply, though the outer veneer can fuzz if you rush. A strip of painter’s tape or a very light chamfer pass before the final depth minimizes that. MDF cuts cleanly but benefits from chip clearing to keep the countersink from polishing the fibers.

The working lengths—roughly 1 to 1.5 inches depending on the bit—cover most furniture and casework screws. If you’re hanging thick hardware or driving unusually long screws, you may need to pre-drill deeper with a separate twist bit after you establish your countersink; the combined pilot simply doesn’t reach as far as a long jobber bit.

In plastic and composites

Plastics reward patience. I tested on acrylic and HDPE scraps and avoided melting by using lower RPM, a light pecking motion, and frequent chip clearing. The bits track straight and produce a clean seat, but if you encounter chatter, slow down and let the flutes cut without side loading. For composite sheet goods and PVC trim, the experience mirrors softwood—clean results at moderate speed. I wouldn’t use these in fiber-cement or anything abrasive; they’re not intended for that.

Drills and a drill press

The 1/4-inch hex shank is handy. It doesn’t spin in a keyless chuck, and the quick-change convenience is real when you’re bouncing among sizes. I primarily used a compact 12V and an 18V cordless drill; both handled the bits smoothly. I did a short run on a drill press for door pulls, setting the table stop for a consistent countersink depth. That repeatability is where the drill press shines—every hole lands with the same finish and seat height.

I don’t recommend these in an impact driver. While the hex fits, the hammering action can loosen set screws and isn’t kind to small pilots.

Durability and maintenance

So far, edge wear is predictable: the pilots dull first, as you’d expect, especially if you contact hidden fasteners or push too fast in hardwoods. The nice part is that the pilots are replaceable. When my #8 pilot lost its bite, I swapped it without fuss and kept the countersink body in service. A drop of light oil on the sliding bore keeps adjustment smooth and helps resist surface rust. Brush off compacted dust from the flutes; it accumulates faster than you think.

Because the countersink body clamps onto the pilot with a set screw, be mindful of marring near the clamping point. Rotate where the screw contacts the bit when you reinstall to avoid digging a groove into one spot over time.

Limitations and small nitpicks

• No micro-depth control: Without a stop collar, precise depth repeatability relies on your drill control or a press. That’s normal for this style but worth noting.
• Two-flute chatter potential: In brittle plastics or super-dense hardwoods, an aggressive feed can induce chatter. Slowing your speed solves it.
• Size coverage: The set covers #6 through #12. If you work a lot with small brass screws (#4 and below), you’ll need a separate solution.
• Working length: On thick stock or long screws, you may need to follow up with a longer twist bit for deeper pilots.

None of these are deal-breakers for general woodworking, but they’re the boundaries of the system.

Tips to get the best results

• Test on scrap to dial countersink depth before touching your workpiece.
• Match speed to material: faster for softwoods, slower for hardwoods and plastics.
• Clear chips often when counterboring deeper than a head-height.
• Use a backer board to avoid exit blowout.
• Recheck the set screw when you change sizes or after a long session.

Bottom line

The Bosch set strikes a useful balance of convenience, adjustability, and clean results. The hex shank makes swapping quick, the replaceable pilots extend the life of the kit, and the adjustable countersink lets you tune the seat exactly how you want it. In wood—including hardwoods and sheet goods—the finish is reliably clean with sensible technique. Plastics and composites also behave if you slow down and clear chips.

Are there fancier systems with stop collars or specialized geometries? Sure. But for everyday cabinetry, jig building, trim installation, and general shop work, this set does the job without fuss and doesn’t mind living in a drill pouch. The limitations—no ultra-fine depth control, a finite working length, and a reliance on a tiny Allen screw—are easy to manage once you know them.

Recommendation: I recommend this set to anyone who needs a straightforward pilot-and-countersink solution for common wood screw sizes. It’s quick to set up, consistent in the materials it’s intended for, and cost-effective over time thanks to replaceable pilots. If you require precise, repeatable depth control across hundreds of holes, pair it with a drill press or look for a stop-collar system; otherwise, this is a dependable, everyday addition to a drill kit.