Property values are typical/nominal figures for guidance and early-stage selection only — exact values vary by temper, grade, supplier and heat treatment. Always confirm critical specifications against a certified datasheet or with an mfgiq engineer before production.
Material is the single choice that locks in most of a custom part's behaviour. Before a single feature is drawn, the material already sets the part's strength and stiffness, its weight, how long it survives corrosion and temperature, how easily it can be machined or moulded, what it costs per part, and — critically — which manufacturing processes are even available to make it. Choose a hardened tool steel and injection moulding is off the table; choose a glass-filled nylon and CNC milling no longer makes sense. Material and process are two halves of one decision.
Getting it wrong is rarely cheap. Over-specifying — reaching for titanium or 316 stainless when 6061 aluminium would have done — quietly inflates raw-material and machining cost on every part you ever make. Under-specifying is worse: a bracket that yields under load, a fitting that pits in salt spray, or a housing that creeps at temperature all show up as warranty returns and field failures, long after tooling is paid for. And some combinations simply cannot be manufactured as drawn — a wall too thin to cast, a geometry too deep to machine in that alloy. The goal of this selector is to surface the handful of materials that genuinely meet your requirements early, while the design is still cheap to change, and to make the trade-offs between them explicit rather than accidental.
Requirements: carries a moderate static load, must be as light as possible, machined from billet in modest volumes, mild indoor/automotive environment, cost-sensitive.
Reasoning: Weight rules out steel, which is roughly three times denser for similar strength. Among the aluminium options, 6061-T6 hits the sweet spot: a good strength-to-weight ratio, excellent machinability (it cuts fast and cleanly, keeping CNC time and cost down), and naturally decent corrosion resistance that improves further with anodising. 7075 is stronger but pricier, less corrosion-friendly and harder to weld — overkill unless the load is high or fatigue-critical. For a general lightweight bracket, 6061-T6 is the default that the filters (low density, mid strength, high machinability, low cost) converge on. Confirm the temper and load case before committing.
Requirements: permanently exposed to salt water or salt spray, structural duty, long service life with little maintenance, appearance matters.
Reasoning: Here corrosion resistance is the hard constraint, not strength or cost. Aluminium and mild steel both suffer in a chloride environment, and even 304 stainless can pit in standing salt water. 316 stainless adds molybdenum specifically to resist chloride pitting, which is why it is the standard for marine hardware. You pay for it in two ways — material cost and poorer machinability (stainless work-hardens and runs slower than aluminium) — but those are acceptable trade-offs when the alternative is a part that corrodes in service. Set the corrosion filter high and the cost filter open, and 316 (and similar duplex grades) is what remains. Validate against the specific exposure and any galvanic pairing in the assembly.
Requirements: tens of thousands of units, low cost per part, enclosure rather than load-bearing structure, dimensional repeatability, reasonable looks.
Reasoning: At high volume the dominant cost is per-part processing, so the question is really material-plus-process. For a non-structural enclosure, injection-moulded ABS is hard to beat: cheap resin, fast cycle times, good surface finish straight from the tool, and easy colouring — the amortised cost per part drops sharply once tooling is paid off. Where the housing needs more rigidity, heat tolerance, EMI shielding or a metallic feel, die-cast aluminium or zinc moves it into metal while keeping the per-part economics of a high-throughput process. Machining either part from solid would be far more expensive at this volume. The selector flags this by pairing a low relative-cost filter with the moulding or casting process filter; pick the resin grade or casting alloy against the real thermal and impact needs.
| Material | Strength (qualitative) | Corrosion resistance | Machinability | Typical use |
|---|---|---|---|---|
| 6061 Aluminium (T6) | Moderate, excellent strength-to-weight | Good (better anodised) | Excellent | Brackets, frames, enclosures, general machined parts |
| 7075 Aluminium (T6) | High — among the strongest aluminium alloys | Fair (worse than 6061) | Good | Aerospace structures, high-stress fittings, tooling |
| Mild / low-carbon steel | Moderate, low cost per unit strength | Poor (rusts unless coated) | Good | Frames, weldments, fabrications, brackets |
| 304 Stainless steel | Moderate-high | Very good (general purpose) | Fair (work-hardens) | Food, kitchen, general corrosion-resistant parts |
| 316 Stainless steel | Moderate-high | Excellent (chloride/marine) | Fair (work-hardens) | Marine, chemical, medical, salt-exposed hardware |
| Brass | Low-moderate | Good | Excellent (free-machining grades) | Fittings, valves, electrical contacts, decorative |
| ABS | Low (plastic), good impact toughness | Good (not for harsh solvents/UV) | Easy to mould/machine | Enclosures, housings, consumer parts |
| Nylon (PA) | Low-moderate, tough and wear-resistant | Good (absorbs moisture) | Good | Gears, bushings, wear parts, fasteners |
| POM / Acetal | Moderate for a plastic, stiff and low-friction | Good | Excellent (machines cleanly) | Precision gears, bearings, low-friction mechanisms |
Strength is expressed qualitatively because it depends heavily on grade and condition (e.g. aluminium temper, steel heat treatment). For numbers, use the selector's comparison table and the supplier datasheet for your exact grade.
Material selection cuts across almost every hardware industry, and the right answer shifts with each one's priorities. Automotive teams balance weight against cost at volume; aerospace pushes strength-to-weight and temperature tolerance to the limit; electronics and consumer products weigh enclosure cost, finish and thermal behaviour; medical device work leans on biocompatible, sterilisable grades like 316L; industrial machinery and robotics trade stiffness, wear life and corrosion against machinability and lead time. The people running these trade-offs are typically design and mechanical engineers scoping a new part, product developers comparing options for a prototype, and sourcing or procurement specialists pressure-testing a bill of materials before committing tooling. For any of them, the selector is a fast way to move from a vague requirement to a concrete, defensible shortlist — which then flows naturally into a process and cost decision.
The selector applies standard materials-engineering practice: it matches your stated requirements — strength, density, corrosion resistance, machinability, cost and service temperature — against typical published property values for each material, and surfaces every option that qualifies. The reasoning is deliberately transparent: you can see which property drove each result, sort by any of them, and put candidates side by side rather than trusting a single hidden "best" answer. What it produces is a starting shortlist, not a final specification. We keep the logic neutral and the data indicative rather than dressing it up with claims we can't stand behind.
Decide which constraint is hardest. If weight and machining cost dominate and the environment is mild, aluminium (often 6061-T6) usually wins on strength-to-weight and lower machining cost. If corrosion resistance, strength or service temperature is the priority — especially salt, chemical or marine exposure — stainless (304 for general use, 316 for chlorides) is worth its higher cost and tougher machining. Add both to the comparison table and look at which rows actually decide your application.
It uses a relative cost rating (1–5) rather than a live price, because real cost depends on grade, form, quantity, region and — heavily — the process used to make the part. Use the cost filter to screen out expensive options, then pair the shortlist with the process and CNC cost tools for a fuller picture. For a firm number on your specific part, request a quote.
When two candidates both pass your filters, let the secondary properties break the tie: look at yield strength, elongation, thermal conductivity and machinability in the comparison table, then weigh them against your real priority (weight, cost, finish or lead time). If the part is load-, safety- or temperature-critical, confirm against the supplier datasheet and, where it matters, test the candidates under real conditions before committing tooling.