What materials are commonly used in sheet metal fabrication?

The short answer

The grades most shops actually hold

Material choice is usually decided by what is available in the required thickness, not by the datasheet. The grades below are the ones stocked as standard sheet in most fabrication shops, which is why quoting tends to land on them.

Steel and stainless: strength against corrosion

Cold-rolled low-carbon steel is the default because it forms easily, welds predictably and costs the least per kilogram. Its weakness is that it has no corrosion resistance of its own, so it either gets a coating or it gets galvanised. Galvanised and galvannealed sheet carry a zinc barrier that survives scratches by sacrificial action, but the coating boils at welding temperature, which is why galvanised assemblies are often riveted or clinched instead.

Stainless works in the opposite direction. Austenitic grades are strong, non-magnetic and resist corrosion through a chromium oxide layer that self-repairs in air. The practical distinction is 304 versus 316: 316 adds molybdenum and is the grade for chlorides, so marine and food-processing environments, while 304 covers general indoor and mildly corrosive service. Both work-harden, which is why stainless springs back more than mild steel and needs more press force or a larger bend radius.

Aluminium, copper and brass: weight and conductivity

Aluminium is chosen for mass, not for strength. 5052 is the fabrication grade because it bends well and resists corrosion in marine air; 6061-T6 is roughly twice as strong but cracks if it is bent on a tight radius, so if a part needs both strength and bends, it is usually designed as 6061 for the flat features and formed in 5052, or heat-treated after forming. Copper C1100 and brass C260 are reserved for conductivity, thermal performance and appearance; they form beautifully but cost several times more than steel and their corrosion products are visible.

How thick, and what each material allows

Thickness availability narrows sharply as thickness rises, and that is a cost and lead-time effect rather than a technical one. Copper and brass top out earliest; stainless and aluminium remain available well past 6 mm but tooling wear and press force climb with them.

Choosing in four questions

Working through these in order resolves most material decisions before a datasheet is opened. Volume sets how much tooling the part can carry, environment sets the corrosion grade, and the last two questions usually pick between two candidates rather than open the field again.

Where material choice goes wrong

• Substituting 6061-T6 for 5052 in a formed part. The strength gain is real; the bend cracking is more real. Heat-treat after forming, or keep 5052.
• Mixing metals that will touch. Copper or brass in contact with aluminium in a wet environment produces galvanic corrosion at the joint. Insulate the interface or pick one family.
• Specifying uncoated steel outdoors. Cold-rolled steel without a coating or galvanising is a maintenance item, not a finished part.
• Ignoring forming direction. Bending across the rolling direction reduces cracking risk by a wide margin compared with bending parallel to it.
• Forgetting finish thickness. Anodising, plating and powder coating all add dimension, which matters on threads and press fits.

Material support at SOMI Custom Parts

We keep carbon steel, galvanised steel, 301 / 304 / 316 stainless, 5052 and 6061 aluminium, copper and brass in the thicknesses our forming and stamping equipment runs, and we will tell you when a substitution changes the process rather than just the price. Send a drawing and a quantity: see sheet metal fabrication, metal stamping, or start with our inquiry form.