Metal Sunglasses Manufacturing: How Metal Frames Are Really Made

The Alloy: Monel, Stainless, Titanium & What They Actually Cost

Every metal frame starts with a choice of alloy, and that choice sets the price ceiling, the weight, and the durability before a single part is formed. Here is the honest tier list, from the factory side.

Monel (nickel-copper). The classic cheap workhorse at $0.80–2.00 a frame. It is easy to form and solder, which keeps labour cost down, and it takes a plate well. The downsides are weight — monel is noticeably heavier — and the nickel content, which can irritate sensitive skin. For promotional, entry-level, and fast-fashion product, monel is the standard choice and there is nothing wrong with it at that price.

Stainless steel. The mid-range value at $2.00–4.50. It is lighter than monel, corrosion-resistant even if the plate wears thin, and it holds a clean chrome or IP finish. This is the tier I steer most brands toward, because it is the point where the extra cost buys a real, feelable improvement in weight and longevity, not just a brand story.

Titanium. The premium tier at $4.50–12.00. Half the weight of monel, hypoallergenic, and extremely resistant to fatigue — a well-made titanium frame will outlast its plating and still hold its shape. It is also harder to form and weld, which is where the price comes from. This is the choice for a high-end or performance product where the light weight is the selling point.

Aluminium. A niche option — very light and cheap to machine, but soft and prone to bending at the bridge. It shows up mostly in low-cost fashion frames and is rarely the right call for anything that will be worn daily.

From Wire to Frame: Forming, Soldering & Assembly

A metal frame is not stamped out of a sheet. It is built from wire and small machined parts, and the sequence matters because each step is a place where a cheap factory can cut a corner you will not see until the warranty claims arrive.

Wire forming. The front and temples start as metal wire that is bent on jigs and dies into shape. The precision of those dies is what gives a frame its symmetry — a sloppy die produces a front where one eye is a millimetre off, and no amount of polishing fixes that. Custom shapes mean new dies, which is the main tooling cost on a metal frame.

Soldering vs spot welding. The bridge and endpieces are joined to the front, and this is the structural heart of the frame. Soldering uses a torch and a lower-melting filler; it is precise and reworkable, and it is what higher-end frames use. Spot welding is faster and cheaper, which is why mass-market frames use it, but a brittle weld will snap under the repeated flex the bridge takes. The honest question to ask is not which method, but how the factory stress-tests the joint — a good one flexes it through thousands of cycles and quotes a failure rate.

Hinges and spring hinges. The hinge is the moving part that fails first on cheap frames. A standard barrel hinge is fine if it is fitted tightly; a spring hinge adds a coil that flexes the temple outward and back, and it is the single best durability upgrade on a metal frame — roughly $0.15–0.30 per pair for a part that prevents the most common breakage.

Nose pads and temple tips. The small soft parts — silicone nose pads, acetate temple tips — are fitted last, and their quality determines the comfort verdict your customer gives in the first week. A frame that is perfect everywhere else but has rock-hard nose pads will be returned for "uncomfortable," and the buyer will never know why.

Electroplating: Where Cheap Metal Frames Go Wrong

If there is one step that separates a $1 metal frame from a $15 one, it is not the alloy — it is the plating. The finish is the first thing the customer sees, the first thing that fails, and the hardest thing to inspect from a photograph.

A proper plating job is a stack, not a single coat. The frame is cleaned, then a copper strike is applied for adhesion, then a nickel layer for body and corrosion resistance, then a top layer — chrome for a bright silver, gold for a gold finish, or an ion plating (IP) layer for the modern matte-black and gunmetal looks. Each layer is microns thick, and together they are what stop the base metal from meeting your skin and the air.

A cheap frame skips the copper strike and puts a single thin nickel or chrome coat straight onto raw brass. That coat is thin and porous, and within weeks it bubbles and flakes, exposing the brass underneath — which then oxidises green against the skin. This is the classic "my sunglasses turned green" complaint, and it is not a mystery to anyone who has seen the plating line. It is a choice, and it is a choice made to hit a price point.

There is also a middle path that is honest: a stainless steel or titanium base needs far less plating to begin with, because the base metal is already corrosion-resistant. A matte IP finish on stainless is one of the most durable combinations in the industry — no heavy chrome to flake, and a base that will not oxidise if it does. If you want a metal frame that still looks new after two summers, the cheap answer is not "more chrome," it is "a better base metal and a lighter finish."

When you source, ask for the plating stack in writing and a salt-spray test result. A factory that plates properly has both; a factory that does not will dodge the question, and that dodge is your signal.

Buying Custom Metal Frames Without Getting Burned

Metal frames have their own version of the "acetate vs injection" trap, and the questions that expose it are different. Here is what to ask and what to write down before you commit to an order.

Specify the alloy, not the colour. "Metal frame" is not a spec. Write "monel," "stainless steel," or "titanium" in the order, and for titanium, ask for the mill certificate. This single line is the difference between a $2 stainless frame and a $4.50 titanium one, and without it you are paying for the story either way.

Specify the plating stack. "Gold finish" is not a spec either. Write the layers — copper strike, nickel, gold — and the thickness, or at minimum require a salt-spray test result. The finish is where cheap frames fail, and it is the cheapest thing to fix in the spec and the most expensive to fix after the fact.

Specify the hinge and the stress test. Spring hinge or standard, and a flex-cycle requirement — a common line is "spring hinge, 10,000 open/close cycles, no loosening." The hinge is the moving part that fails first, and a dated requirement is what turns it from a hope into a commitment.

Use an existing wire front to skip tooling. The tooling on a metal frame is the wire-forming dies, and they are $1,000–3,000 for a custom shape. But if you use a catalogue front and change only the finish, lens, and logo, the MOQ drops from 500–1,000 pairs to 300–500 and the tooling cost mostly disappears. For a first order, this is almost always the right call — you are buying a product that already works, not betting on a die you have not sold yet.

The brands that get hurt on metal frames are rarely the ones that paid too much. They are the ones that ordered "metal frames, gold finish" and discovered six months later that the gold was a single thin coat over brass, and the alloy was whatever the factory had lying around. Write the alloy, the plating, and the hinge, and the rest of the order takes care of itself.

Frequently Asked Questions