Brass plates and strips for watches
Brass sheet and strip for watches are core materials for precision watch movements and exterior components. They offer excellent processing properties, wear resistance, and a beautiful golden color, making them widely used in mechanical watches, quartz watches, smartwatches, and other applications. Key grades include H62, H65, and H68. H62 brass, with a copper content of 60.5-63.5%, offers high strength (tensile strength ≥300 MPa) and is suitable for gears and springs. H65 brass, with a copper content of 63.5-68.0%, offers excellent plasticity and is used for dials and hands. H68 brass, with a copper content of 67.0-70.0%, offers a brighter color and is suitable for watch cases and straps. Sheet thickness ranges from 0.1-2 mm, strip thickness from 0.05-0.5 mm, and widths from 10 to 200 mm. Dimensional tolerances range from ±0.001 mm, with a surface finish of Ra ≤ 0.02 μm, which can be polished to a mirror finish (Ra ≤ 0.01 μm).
The production process for brass sheet and strip for watchmaking represents the pinnacle of precision copper processing, requiring constant control of accuracy and surface quality. First, electrolytic copper (99.95%) and zinc ingots (99.9%) are smelted in a medium-frequency induction furnace at 1080-1120°C. Trace amounts of rare earth elements (0.01-0.03%) are added to refine the grain size. The ingots are continuously cast at a cooling rate of ≥80°C/min, resulting in uniform, fine grains (≤10μm). After hot rolling to a thickness of 1-3mm, they undergo multiple cold-rolling passes with a total reduction of ≥90% at a rolling speed of 20-50m/min. A 20-high mill is used to maintain flatness (≤0.05mm/m). Intermediate annealing is performed under nitrogen at 400-450°C to eliminate work hardening and prevent oxidation. After finishing, the steel is degreased (oil film ≤ 1mg/m²) and bright annealed (300-350°C) to maintain a hardness of HV80-120, facilitating precision machining. Finished products undergo microstructural testing (for inclusion-free) and dimensional accuracy verification to ensure compliance with watchmaking standards.
In mechanical watch movements, brass plates and belts are key materials for transmission components. The gear train utilizes 0.1-0.3mm thick H62 brass belts, stamped and hobbed to achieve IT5 tooth profile accuracy. This allows the movement of a Swiss brand mechanical watch to maintain a timekeeping error of ±5 seconds per day. The mainspring utilizes 0.05-0.1mm thick H65 brass belts, with an elastic limit of ≥250MPa and a fatigue life exceeding 100,000 cycles. This extends the power reserve of one mechanical watch to 72 hours. The bridges and jewel bearings utilize 0.5-1mm thick H62 brass plates with a flatness of ≤0.01mm, ensuring precise fit between movement components. This has resulted in a 99.5% assembly pass rate for one high-end mechanical watch.
Watch exterior components place extremely high demands on the color and processing performance of brass sheet metal. Watch cases utilize 1-2mm thick H68 brass sheet, which is stamped, polished, and then electroplated with rose gold or platinum. The coating achieves 5B adhesion (no peeling in a scratch test), and the case of a luxury brand watch achieves a 3H scratch resistance rating. Dials utilize 0.3-0.5mm thick H65 brass strip, with graduations formed through etching and enameling, achieving a pattern accuracy of ±0.01mm. This has reduced the dial rejection rate for a fashion brand’s watches to 0.3%. Smartwatch metal frames utilize 0.5-1mm thick H62 brass strip. After CNC processing, the weight is kept below 5g, resulting in a 10% increase in battery life for a tech company’s smartwatches.
As the watch industry evolves towards high-end and personalized design, the performance of brass plates and strips continues to innovate. A manufacturer has developed antibacterial brass plates (added with 0.1-0.3% silver ions) with an E. coli inhibition rate of ≥99%, resulting in a health watch receiving food-grade safety certification. To meet the demand for vintage watches, an antique brass strip (added with 0.5-1.0% lead) has been developed. After oxidation, it creates a distressed effect, resulting in a market premium of 30% for a vintage brand watch. Laser engraving technology enables micron-level patterns to be created on 0.05mm thick brass strips, shortening the personalized design cycle for a custom watch to just 7 days. In the future, with the application of 3D printing technology, brass plates and strips for watches will become ultra-thin (≤0.03mm) and feature multiple functions (conductive + antibacterial), enabling endless possibilities in watch design.
