Design

How to Specify Cutouts and Openwork in Custom Metal Products

Why Cutouts Fail in Production

Cutouts and openwork look simple in artwork, but they are where many custom metal jobs fail. A shape that looks clean on screen can turn fragile once it is reduced to a 0.8 mm steel die line, plated at 0.1 to 0.2 microns of gold or nickel, and stamped into zinc alloy or brass. The common problems are broken bridges, distorted inner windows, trapped enamel, and edges that feel sharp even when the design passes visual approval.

For buyers, the practical issue is not just appearance. A design with too many narrow connections may raise scrap, increase tool wear, and push the order from a normal MOQ of 100 to 300 pieces into a higher-risk run that needs 500 pieces or more before it is economical. At ZheCraft, we usually treat openwork as a manufacturability question first and a graphic question second, because the tool path, alloy choice, and plating process determine whether the part survives repeated production.

Set Minimum Bridge Widths and Slot Sizes

The first specification to lock down is bridge width, meaning the narrowest metal connection between two cutout areas. For stamped brass or iron pins around 25 to 35 mm wide, a safe bridge width is usually 0.9 to 1.2 mm. For larger challenge coins or badge-style products, 1.2 to 1.5 mm is more forgiving, especially if the item will be soft enamel filled and polished. If you go below 0.7 mm, the part may look elegant in rendering but becomes prone to bending, incomplete fill, or breakage during polishing and packing.

Slot width should also be specified, not assumed. For laser-cut acrylic inserts or metal windows, 0.8 mm slots are often the practical floor for stable production, while 1.0 mm is a better target if the edge must accept plating and hand finishing. If a supplier quotes a tight decorative gap like 0.4 to 0.5 mm, ask whether that gap is before or after plating, because 0.1 to 0.15 mm of build on each side can close the gap more than you expect.

• Bridge width: 0.9 to 1.2 mm for small pins; 1.2 to 1.5 mm for coins and badges
• Slot width: target 0.8 to 1.0 mm minimum for stable openwork
• Keep internal corners with a radius of at least 0.15 to 0.25 mm when possible
• Avoid long unsupported spans above 12 to 15 mm without a reinforcing bar or thicker border

Choose the Right Base Material and Thickness

Material choice changes what kind of cutout is realistic. Zinc alloy is flexible for complex 3D forms, but thin openwork sections can warp if the cross-section drops below 1.0 mm in critical areas. Brass and iron are better when you need crisp die-struck edges and narrow piercings, because they hold detail more predictably in 1.0 to 1.5 mm stock. For most pins, badges, and small keychains, 1.2 mm thickness is the sweet spot; 1.5 mm is stronger but adds weight and can make fine cutouts look heavy.

If the product is a challenge coin, keep in mind that deep relief and open center windows fight each other. A 45 mm coin with a pierced center may need a thicker rim, often 2.5 to 3.0 mm, to stay rigid and to leave enough surface for plating and polishing. For soft enamel, the exposed metal border around a cutout should usually be at least 0.3 mm visible after polish, otherwise the edge can blur under the lacquer and appear uneven after plating.

Specify Edge Geometry, Relief, and Surface Finish

Buyers often define the silhouette but not the edge quality. That is a mistake. If the part has visible cutouts, specify whether you want a square-cut industrial edge, a softened tumble-polished edge, or a hand-buffed edge with a slight break. A normal target tolerance for outside dimensions is plus or minus 0.2 mm for small stamped items and plus or minus 0.3 mm for larger cast pieces, but the visual edge is still influenced by polish direction and plating thickness.

Relief depth matters when cutouts sit near raised areas. For die-struck products, a relief height of 0.3 to 0.5 mm can preserve the visual hierarchy without creating a fragile web. If the relief is deeper than 0.6 mm and the cutout is adjacent to it, polishing can round the intended crisp line. For plating, common specs are 0.1 to 0.3 microns for decorative gold flash and 0.3 to 0.5 microns for nickel or antique finishes, but buyers should note that heavy antique washes can visually reduce cutout clarity if the recesses are too narrow.

Use a Spec Table to Compare Common Openwork Builds

The right construction depends on whether the item is being stamped, cast, laser-cut, or assembled from multiple parts. Below is a practical comparison that buyers can use when deciding how far to push cutouts without inviting rework. It is not a universal rulebook, but it reflects the range we see most often in factory quoting for custom metal products.

Build type	Best use case	Practical minimums	Typical FOB price range
Stamped brass pin	Flat logo pins with pierced windows	1.2 mm thickness, 0.9 mm bridges, MOQ 100 to 300	USD 0.65 to 1.60 per pc
Zinc alloy cast badge	3D shapes with moderate open areas	1.5 mm local wall thickness, 1.0 mm openings, MOQ 300 to 500	USD 1.20 to 3.80 per pc
Die-struck challenge coin	Wide open center or cutout rim	2.5 mm rim, 1.2 mm bridge, MOQ 100 to 300	USD 1.80 to 4.50 per pc
Laser-cut keychain insert	Fine silhouettes and text windows	0.8 to 1.0 mm slots, MOQ 200 to 500	USD 0.90 to 2.20 per pc

The main takeaway is that the cheapest-looking structure on a drawing is not always the cheapest finished part. A stamped brass pin with well-placed piercings can cost less than a cast zinc alloy version that needs extra cleanup and rework. On the other hand, if the design has layered depth, a cast build may save money by reducing assembly steps even though the unit price is higher at first glance.

Plan for Artwork, Tooling, and Sample Review

Openwork needs a cleaner artwork handoff than a solid silhouette. Deliver vector files with every cut line closed, every negative space named, and every internal gap dimensioned. If the design has repeated slots, specify one master dimension and allow a tolerance band, such as 1.0 mm nominal with plus or minus 0.1 mm, instead of leaving the factory to interpret symmetry from a bitmap. For complicated structures, a simple line note stating what must remain connected after die cutting saves time and reduces sample revisions.

Tooling should be approved against a physical or high-resolution sample, not only a rendering. A good pre-production sample for a cutout pin or badge should be checked under 5x magnification for burrs, plating bridge-over, edge tearing, and any blocked openings. AQL 2.5 is a reasonable general inspection target for cosmetic defects, while AQL 1.0 is more appropriate if the cutout is structural or if the part will be assembled into a premium gift set. For production lots above 3,000 pieces, ask for a first-article approval from the same cavity or die position that will be used in the main run.

Checklist for Buyers Before You Confirm the PO

Use this checklist before releasing the order. It prevents the most common disputes and makes supplier quotes easier to compare on equal terms.

• State the base material: brass, iron, zinc alloy, stainless steel, or acrylic insert
• Define the minimum bridge width and minimum slot width in millimeters
• Specify nominal thickness and whether plated thickness is measured before or after finishing
• Note the acceptable dimensional tolerance for outer size and internal cutouts
• Confirm whether edges should be sharp, tumbled, or hand-polished
• Request the plating type and finish level, including antique wash if used
• Ask for sample inspection criteria, including AQL level and defect definitions
• Confirm MOQ tier, lead time in days, and whether tooling cost is separate from unit price

If any of these items are missing, suppliers will fill the gap with their own process assumptions. That is where orders become inconsistent between sample and mass production. In practice, the cheapest way to buy openwork is to be specific early, because every later clarification costs either time, new tooling, or a higher rejection rate.

What to Do Next

If your current design has cutouts, send the supplier a dimensioned vector file, a bridge-width note, and one reference photo showing the finish level you expect. Ask for a quote at two MOQ tiers, for example 100 and 500 pieces, and request the supplier to state the minimum manufacturable slot width and expected lead time in days. For ZheCraft-style metal products, that simple comparison usually reveals whether the concept should be stamped, cast, or simplified before sampling.

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