3D Printing Nozzles: Brass vs Hardened Steel vs Ruby and When to Use Each

A 3D printer nozzle costs between $2 and $100, weighs a couple grams, and sits at the single most critical point in your entire print path—the spot where solid filament becomes molten plastic. Despite that, most people run whatever nozzle shipped with their printer until it’s so worn the prints look fuzzy. Understanding nozzle materials isn’t just gear-nerd trivia; it directly affects your dimensional accuracy, surface finish, and which filaments you can run without destroying hardware.

I’ve tested brass, hardened steel, and ruby-tipped nozzles side-by-side on my A1 Mini over four months, tracking wear patterns, thermal performance, and print quality. Here’s what the data says.

Brass Nozzles: The Default for Good Reason

Brass (typically C36000 free-machining brass) is the stock nozzle material on virtually every FDM printer. There’s good engineering behind that choice: brass has a thermal conductivity of roughly 115 W/m·K, which means it transfers heat from the heater block to the filament efficiently and evenly. That fast heat transfer gives you consistent melt temperatures across different flow rates.

For non-abrasive filaments—standard PLA, PETG, ABS, and TPU—brass is excellent. It’s cheap ($2–5 per nozzle), machines to a precise orifice size, and delivers the best thermal performance of any common nozzle material.

The weakness is hardness. Brass sits at roughly 3 on the Mohs scale. Any filament with abrasive additives—carbon fiber, glass fiber, glow-in-the-dark particles, wood fill, or metal fill—will erode the nozzle bore. I measured a 0.4 mm brass nozzle that grew to 0.52 mm after just 500g of carbon-fiber PETG. That 30% increase in bore diameter means your slicer thinks it’s laying down 0.4 mm lines, but the nozzle is actually extruding 0.52 mm—killing dimensional accuracy and creating rough surfaces.

Hardened Steel Nozzles: The Abrasive Fighter

Hardened steel nozzles (A2 tool steel, hardened to 60+ HRC) solve the wear problem. Their Mohs hardness of roughly 7–8 makes them nearly immune to abrasive filaments. The same carbon-fiber PETG that destroyed my brass nozzle in 500g showed zero measurable bore change after 2 kg through a hardened steel nozzle.

The tradeoff is thermal conductivity. Hardened steel conducts heat at roughly 25–30 W/m·K—about 4x worse than brass. In practice, this means:

Slower heat transfer: The filament takes slightly longer to reach melt temperature inside the nozzle. At low to moderate flow rates (under 15 mm³/s), you won’t notice a difference. At high flow rates (20+ mm³/s), you may need to bump nozzle temperature 5–10°C higher than your brass settings to avoid under-extrusion.

Slower response to temperature changes: If your printer does active temperature adjustments between layers (like Bambu Lab’s dynamic flow control), steel nozzles respond more sluggishly. Again, for most prints this is academic—but at extreme speeds it becomes measurable.

Cost is reasonable at $8–15 per nozzle. For anyone printing abrasive materials regularly, a hardened steel nozzle pays for itself in 1–2 spools by not needing replacement.

Ruby-Tipped Nozzles: The Premium Option

Ruby nozzles (like the Olsson Ruby) use a brass body for thermal conductivity with a synthetic ruby insert at the tip. Ruby scores 9 on the Mohs scale—just below diamond. The result is near-zero wear from any filament combined with the thermal performance of brass. It’s the best of both worlds, engineering-wise.

After 3 kg of carbon-fiber nylon through my Olsson Ruby, the bore measured exactly 0.40 mm—identical to new. The print quality with abrasive filaments is indistinguishable from a fresh brass nozzle, which is exactly the point.

The catch is price: $85–100 per nozzle. That’s 10–20x the cost of a hardened steel nozzle. The math only works if you print large volumes of abrasive filament. At $12 per hardened steel nozzle and replacement every 2–3 kg of CF material, you’d need to print roughly 15–20 kg of abrasive filament before the ruby pays for itself versus rotating steel nozzles.

For most hobbyists, that’s 1–2 years of printing. For production environments running carbon fiber daily, the ruby makes economic sense within a few months.

Nozzle Size: 0.4 mm Isn’t Always Best

While we’re talking nozzles, size matters as much as material. The standard 0.4 mm bore is a good all-around choice, but other sizes have distinct advantages:

0.2 mm: Finer detail, sharper corners, better text legibility on small prints. But flow rate drops to roughly 25% of a 0.4 mm nozzle, so prints take 3–4x longer. Great for miniatures and detailed models.

0.6 mm: My personal sweet spot for functional parts. 50% more flow than 0.4 mm, which means significantly faster prints with only a minor loss in fine detail. Layer adhesion improves because wider extrusion lines bond to adjacent lines over a larger surface area. Structural parts printed at 0.6 mm are noticeably stronger.

0.8 mm and 1.0 mm: Speed demons for vases, large containers, and rough prototypes. A 0.8 mm nozzle at 0.4 mm layer height prints about 4x faster than a 0.4 mm nozzle at 0.2 mm layer height. Surface quality is visibly coarser, but for non-cosmetic parts, the time savings are enormous.

When to Replace Your Nozzle

Knowing when a nozzle is worn saves you hours of troubleshooting mysterious print quality issues. Replace your brass nozzle if:

First layers look inconsistent: If your bed leveling is confirmed good but first layers show thin spots and fat spots, the bore is likely oval from wear. A worn nozzle doesn’t extrude a round cross-section anymore.

Dimensional accuracy drops: Print a 20 mm calibration cube. If X and Y dimensions are consistently 0.2+ mm over target, the nozzle bore has widened.

Stringing increases: A larger bore leaks more material during travel moves. If your retraction settings haven’t changed but stringing has worsened, check the nozzle.

Surface texture changes: Worn nozzles create an inconsistent, slightly rough surface texture that’s different from the clean layer lines of a sharp nozzle.

My Recommendation by Use Case

PLA and PETG only: Stick with brass. Buy a 10-pack of 0.4 mm nozzles for $8 and replace every 3–6 months or whenever quality degrades. It’s the cheapest, highest-performance option for non-abrasive materials.

Occasional abrasive filaments: Keep one hardened steel nozzle ($12) and swap it in when you run carbon fiber, glass fiber, or glow-in-the-dark filament. Swap back to brass for regular PLA/PETG to maintain the best thermal performance.

Frequent abrasive materials: Run hardened steel full-time. The 5–10°C temperature bump is a minor inconvenience compared to replacing brass nozzles every few hundred grams. If you’re running a print farm or production setup with CF nylon, consider the ruby for its set-and-forget longevity.

Your nozzle is a consumable, not a permanent fixture. Treat it like a drill bit—use the right material for the job, replace it when it’s dull, and your prints will stay sharp.