Bosch 19/32 in x 1/2 in carbide-tipped bullnose router bit

Why I reached for this bullnose bit

On a recent batch of painted shelves and a few pine window sills, I wanted a fully rounded, comfortable edge that wouldn’t need much cleanup. I pulled out Bosch’s 19/32-inch bullnose bit (1/2-inch shank) and ran it through its paces on the router table and with a handheld router. It’s a straightforward cutter—no frills, no bearing—built around micrograin carbide with a hardened steel shank. What matters is how true it runs, how clean it cuts, and how well it holds an edge. On those fronts, it did exactly what I needed.

Fit, finish, and setup

Out of the box, the bit’s grind looked even and crisp. The cutting edges were consistent, with no visible chips and a uniform polish on the carbide. The 1/2-inch shank seated solidly in both my table-mounted router and a plunge router; runout was minimal. I always do a light test spin before committing to a cut—no odd vibration or whirring, which is what I want to feel from a bit with some mass.

Because this is a non-bearing bullnose, you’ll want either a router table fence or a reliable edge guide. I prefer the table for bullnose work because centering the profile on the stock’s thickness is simpler and safer. With a straight fence, I set the fence faces flush with the widest part of the bit’s profile, then dialed height so the midpoint of the radius aligned roughly with half the stock thickness. A test piece or two is essential to align the profile perfectly.

What the 19/32 size really means

This size is built to make a full bullnose on 19/32-inch material—essentially the actual thickness of “5/8-inch” plywood and some shelf boards. If your stock matches the bit’s diameter, you can round both edges into one continuous half-round. On thicker stock (say, 3/4-inch or a full tread thickness), you’ll still get a pleasant, large-radius roundover, but it won’t be a perfect full bullnose. Match your bit to your material if a true centerline bullnose is critical.

For window sills, shelf edges, and trim that will be painted or clear-coated, this size is particularly nice: it gives a generous feel in the hand without looking oversized. On stair treads, it works if you’re going for a softer arris rather than a fully centered bullnose; for a true tread bullnose, you’d want a larger diameter.

Cut quality and surface finish

The micrograin carbide delivered the kind of finish I expect from a premium bit: crisp, repeatable, and smooth. On poplar and pine, I got a surface that needed only a light pass with 220-grit before primer. In hard maple, the cut remained clean with minimal fuzzing on the exit. I saw no chip-out on face grain with a sensible feed rate and sharp bit. End grain can be tricky with full-profile cutters; climb-cutting a light pass on the end first, then a standard pass, kept blowout in check. The bit cleared chips well, and I didn’t get the scorched stripes you can see when the carbide overheats or the grind isn’t efficient.

To minimize sanding, I ran two lighter passes rather than one heavy cut. First pass slightly off-center, flip the board, second pass to meet in the middle. That spreads the load and reduces the chance of burning in resinous softwoods.

Speeds, feeds, and control

• Router speed: I had good results around 16,000–18,000 RPM. Slower than a small straight bit, but not so slow that the cut chatters.
• Feed rate: Moderate and steady. Push too slowly and you risk heat/burn; too fast and you’ll telegraph vibration. The 1/2-inch shank helps keep chatter down.
• Pass strategy: Two passes for full-profile engagement on matching stock thickness. If you only need a large roundover, one pass is fine with conservative depth.
• Workholding: Featherboards on the table fence and top kept the cut consistent along the length, which matters with a profile that must meet in the center.

With a handheld router, I relied on an edge guide and took lighter bites. In that setup, keeping the base flat and pressure steady is key to preserving the profile’s symmetry.

Performance on different materials

• Pine and poplar: Clean edges, minimal fuzz. No burning when I kept the feed moving.
• Maple and oak: Smooth finish with crisp arrises where the radius terminates. A light climb pass on ends eliminated tear-out.
• Plywood and MDF: MDF was a breeze, unsurprisingly, and this size is spot-on for 19/32 “5/8-inch” plywood. The bit left a paint-ready surface with very little post-routing cleanup. As always, watch for staples near edges in shop-grade ply—carbide doesn’t forgive hardware strikes.

Durability and edge retention

After a few dozen edges across softwoods and a handful in maple, the bit still felt sharp to the fingernail and produced the same sheen on freshly cut surfaces. That lines up with what micrograin carbide and a good heat-treatment should deliver. I make a habit of cleaning pitch and resin with a dedicated bit cleaner; keeping the edge clean reduces heat and preserves sharpness. If you hone your bits, a few strokes with a fine diamond card on the flat faces brings the edge back without changing the profile.

Precision and consistency

A bullnose profile exposes any runout or fence setup inconsistency instantly—you’ll see a faint flat at the apex or a ridge where passes meet. This bit’s grind symmetry made it easy to center. Once I dialed the height, the top and bottom curves met cleanly without a step. On long shelf runs, the profile remained uniform from end to end, which tells me the bit is balanced and the shank is true.

What I’d change

• No bearing option: A bearing can be handy for curved work or quick passes on irregular stock. This bit expects a fence or guide. That’s normal for full bullnose cutters, but it’s worth noting if you don’t have a router table.
• Size specificity: This 19/32 diameter is perfect for true 5/8 nominal material. If your shop runs mostly 3/4 stock, you’ll want the corresponding larger size for a true centerline bullnose. That’s not a knock on the bit—just pick the right diameter for your material.

Safety and technique tips

• Use the 1/2-inch shank fully seated, backing off about 1/8 inch so it doesn’t bottom out in the collet.
• Let the bit come to full speed before engaging the work.
• Consider a light climb pass on end grain to prevent blowout, followed by a standard pass.
• For a full bullnose on matching thickness, make two lighter passes—flip the board to split the cut.
• Keep the bit clean; pitch buildup causes heat, which leads to burning and shorter edge life.

Who this bit suits

• Cabinet and trim pros shaping window sills and shelf edges that match 5/8 nominal thickness.
• DIYers building painted built-ins where comfort and a friendly edge profile matter.
• Anyone needing a reliable, durable bullnose cutter that runs true on a 1/2-inch shank.

If you often work in 3/4 stock or need bearing-guided curves, this exact size and format may be less ideal. Bosch offers other diameters, and bearing-guided roundovers may be more flexible for curved edges.

Recommendation

I recommend this Bosch bullnose bit for clean, consistent, and durable bullnose work on 19/32 (5/8 nominal) material. It runs true, the micrograin carbide holds an edge, and the finish it leaves significantly reduces sanding. Paired with a router table and a well-set fence, it makes producing a full, centered bullnose straightforward and repeatable. If your projects are mostly 3/4-inch stock or you rely on bearing-guided cuts, choose a different diameter or a different style. For 5/8 shelves, sills, and trim, though, this bit is exactly the right tool.