Brass CW508L (CuZn37)

Physical properties

Laser processing

Extremely toxic. Zinc oxide fumes (ZnO) are released during processing—these cause 'metal fume fever' (flu-like symptoms, chills, fever). Copper fumes are also toxic. A professional extraction system with HEPA+activated carbon is mandatory. Never process brass without extraction, not even for 30 seconds.

CO₂: Not cuttable. Brass is highly reflective to the CO2 laser wavelength (10.6 µm). The beam reflects off the polished surface with >95% efficiency, effectively returning energy to the optics. This causes immediate lens damage and risks destroying the laser tube. CO2 laser engraving is also not practical on brass without specialised marking compounds (e.g., TherMark or CerMark).

Diode: Possible with 20W+ diode lasers on painted or blackened surface only. The polished brass must be coated with a dark, non-reflective layer (black spray paint or special marking spray). The laser heats the coating which transfers heat to engrave/anodize the surface. Thickness limit ~0.5–1mm; not practical for real structural cutting.

Fiber: Fiber laser (1.06 µm wavelength) cuts brass up to 3–4mm excellently. Brass CW508L has 37% zinc: controlled cutting parameters are needed to avoid excessive zinc vaporisation (white residues on the cut edge). Excellent edge quality with clean gas assist (nitrogen for bright finish, compressed air for production). Fiber engraving gives a dark, permanent mark without coatings. The ideal choice for brass marking and cutting.

CNC / milling processing

Excellent CNC machinability. CW508L is a cold-forming brass with good chip formation. Use uncoated carbide bits for fine detail and HSS for simple profiling. Recommended chipload: 0.03–0.08mm/tooth for micro-milling. Lubrication recommended (oil mist or WD-40) to prevent chip welding and improve surface finish.

Post-processing

Sanding: Sands easily with standard abrasives. Grits 320 → 600 → 1200 for a satin finish. For a mirror polish, follow with wet sanding up to 3000 grit + polishing paste. Brass is relatively soft and heats up quickly: avoid burnishing the surface.

Primer: mandatory. A specific metal primer for non-ferrous metals is required. Standard iron primers do not adhere well. Epoxy or polyurethane metal primer recommended. Degrease with acetone before application.

Gluing: Soldering/brazing is the standard method. For adhesives: epoxy structural adhesives (e.g., Araldite) work well. Cyanoacrylate (superglue) gives weak bonds due to poor shear strength on smooth metal. Sand the glue zone for better adhesion.

Seasoning: Store in a dry environment. Avoid contact with acids, ammonia, and chlorides (including sweat from hands). Handle with latex or cotton gloves if a mirror finish must be preserved.

Over time: Brass oxidises and tarnishes to a brown-yellow patina within weeks in indoor air. In humid environments, it forms green-blue verdigris (copper carbonate). To preserve a bright finish, apply a clear protective lacquer (e.g., Incralac) or Renaissance Wax. The patina is often desirable for aesthetic/steampunk projects.

Common defects

• Long chip that wraps around the cutter if cutting parameters are not optimised for lead-free brass
• Rapid oxidation stains when handled with bare hands without gloves

Safety

Recommended PPE: eye_protection, mask_p2

Zinc fumes are hazardous. Always extract. Brass dust from CNC machining is not explosive like aluminium but still requires FFP3 protection. Small chips are sharp and can penetrate skin.

Availability and formats

Commercial formats: sheets 0.5–5mm, strips for deep drawing, flat bars

Related materials

Sources

• EN 1652 — Copper and copper alloys (CW508L sheet and strip)
• MatWeb — Brass UNS C26000 (70/30 Cartridge Brass) Datasheet