Brass Luggage Rivet Eyelet Stamping with Decorative Finish
title: "Brass Luggage Rivet Eyelet Stamping with Decorative Finish" description: "Brass stamping of decorative rivets for luggage hardware. Progressive die design, burnishing, antique coloring, lacquer coating, and abrasion testing." keywords: "brass luggage rivet, decorative eyelet stamping, antique brass finish, luggage rivet hardware, brass stamping eyelet" filename: "brass-luggage-rivet-eyelet-decorative-stamping" tags: "brass luggage rivet, decorative eyelet, stamping, antique brass finish, luggage hardware, rivet manufacturing, progressive die, burnishing" scode: "5" "
Luggage rivets and eyelets serve both functional and decorative purposes — they secure straps and corners while enhancing the visual appeal of the product. For fashion luggage brands, the aesthetic quality of these small brass components directly influences the perceived value. This case study describes the manufacture of decorative brass rivets and eyelets through progressive die stamping with an antique brass surface finish, developed for a premium fashion luggage line targeting the Asia-Pacific market.
Product Design and Aesthetic Requirements
The rivet set consists of a dome head (Ø12 mm, 3.5 mm height) with a hollow shank (Ø4 mm, 4 mm length), and a mating eyelet with a flared flange (Ø10 mm) and a rolled barrel. The customer specified an antique brass finish with darkened recesses and highlighted raised surfaces to create a vintage look, with a minimum of six months of wear resistance against normal handling and cleaning.
| Parameter | Rivet Specification | Eyelet Specification |
|---|---|---|
| Base material | C26000 brass (70/30) | C26000 brass (70/30) |
| Material thickness (mm) | 0.8 | 0.6 |
| Head diameter (mm) | 12.0 ± 0.15 | 10.0 ± 0.15 (flange) |
| Shank/barrel OD (mm) | 4.0 ± 0.08 | 4.1 ± 0.08 |
| Overall length (mm) | 7.5 ± 0.15 | 5.5 ± 0.15 |
| Surface finish | Antique brass, dark recess | Matching antique brass |
| Wear resistance | ≥ 6 months normal use | ≥ 6 months normal use |
The antique brass aesthetic requires a multi-step surface finishing sequence that combines chemical coloring, mechanical highlighting, and a protective clear coating. Each rivet pair must present a consistent color and texture across the production run.
Progressive Die Stamping Process
Both the rivet and eyelet are produced on separate progressive dies operating at 50 strokes per minute on a 60-ton high-speed press. The rivet die has 8 stations while the eyelet die has 6 stations, each performing sequential forming operations from the brass strip.
The rivet progressive die begins with pilot hole piercing at station 1, followed by progressive drawing of the dome head at stations 2–4. Because the dome head requires significant material stretching, an intermediate annealing station could not be integrated in-die, so the brass strip is procured in the soft annealed condition (O-temper). Station 5 reverse-draws the shank cavity, and station 6 reduces the shank OD to the final 4.0 mm through ironing. Station 7 pierces the center hole, and station 8 cuts the part free.
| Station | Rivet Operation | Eyelet Operation |
|---|---|---|
| 1 | Pilot hole + blank development | Pilot hole + blank development |
| 2 | Dome head pre-form (shallow draw) | Flange pre-form (cup drawing) |
| 3 | Dome head full-form (deep draw) | Flange full-form + barrel start |
| 4 | Shank cavity reverse drawing | Barrel ironing (OD sizing) |
| 5 | Shank ironing (OD sizing) | Center hole piercing |
| 6 | Center hole piercing | Barrel curling + part cut-off |
| 7 | Top dome burnishing | — |
| 8 | Part cut-off | — |
A burnishing station at position 7 (rivet die) uses a polished carbide tool to compress and smooth the dome surface, achieving Ra 0.4 μm finish without additional polishing. This step is critical because surface imperfections at this stage are magnified by the subsequent antique brass finishing process.
Decorative Antique Brass Finishing
The antique brass finish is achieved through a five-step chemical and mechanical process. After stamping, all parts undergo a 10-minute alkaline soak cleaning followed by acid activation in 10% sulfuric acid for 30 seconds.
The coloring process uses a potassium persulfate-based solution (30 g/L at 80 °C) that forms a brown to black copper oxide layer on the brass surface. Immersion time of 3–5 minutes produces a dark brown color, with longer times trending toward black. The parts are removed while the recesses remain fully darkened.
Mechanical highlighting follows: the parts are tumbled in a vibratory bowl with 5 mm ceramic media and a mild abrasive compound for 8 minutes. This selectively removes the oxide layer from raised surfaces while retaining the dark color in recesses. The result is the desired antique brass appearance: bright highlights on the dome crown and eyelet flange, with dark accents in the lettering grooves and perimeter.
| Finishing Step | Duration | Temperature | Result |
|---|---|---|---|
| Alkaline soak cleaning | 10 min | 65 °C | Removes oil and stamping lubricant |
| Acid activation (10% H₂SO₄) | 30 sec | Ambient | Activates surface for coloring |
| Antique coloring (persulfate bath) | 3–5 min | 80 °C | Dark brown oxide layer |
| Vibratory highlighting | 8 min | Ambient | Selective oxide removal on raised areas |
| Clear lacquer spray | — | Oven cure 110 °C, 15 min | Protective transparent coating |
A clear acrylic lacquer (8–12 μm dry film thickness) is applied by automated spray in a Class 10,000 cleanroom booth, followed by oven curing at 110 °C for 15 minutes. The lacquer seals the antiques finish against tarnishing and provides the required six-month wear resistance.
Quality Control and Wear Testing
Color consistency is evaluated using a spectrophotometer with CIE Lab measurement. The target L value for the dark recess is 28–32, while the highlighted area should measure L 62–68. Rejects occur if any part deviates beyond ±3 L units from the approved standard.
Abrasion resistance is tested using a Crockmeter with a dry cotton cloth under 9 N load for 50 cycles. The antique finish must show no visible color reduction on the rubbed area. In production validation, 100% of tested parts passed this criterion, with measurable color change (ΔE) remaining below 1.5 after the test.
Production yield stabilized at 95.2% after initial process tuning. The primary reject causes were inconsistent oxide coloration (2.1%, mostly from bath temperature fluctuations during shift changes), highlighting over-polish (1.5%), and lacquer orange-peel defects (0.7%). Installation of automatic bath temperature control with ±0.5 °C accuracy reduced the color variation rejects to 0.8% in subsequent production months.
For luggage OEMs requiring decorative brass hardware with consistent antique aesthetics at high volumes, the combination of progressive die stamping with chemical-mechanical surface finishing provides a proven production path. The key to success lies in strict process control at the coloring stage and precision burnishing at the stamping stage.
