how to choose material for machined part
How to Choose a Material for a Machined Part
Material selection goes wrong when it starts with a familiar name instead of the service condition. Most buyers arrive with 6061 or 304 in mind because those are the names they know, and the part then carries an assumption rather than a decision. The order below takes five minutes and produces a material that can be defended.
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- First question
- What does the part touch?
- Second
- What load and temperature?
- Third
- What has to happen to the surface?
- Fourth
- What quantity and budget?
Material selection is a sequence of eliminations, not a search for the best material. The best material is the one that satisfies every requirement with the least unnecessary cost.
Specifications
| General purpose metal | Aluminium 6061-T6 — light, machinable, anodizable |
|---|---|
| Corrosion + machining | Stainless 303 — free-cutting, but not weldable |
| Weldable stainless | 304 / 316L |
| Hardening and cost | Carbon steel 1045 |
| General purpose plastic | POM (acetal) or ABS |
| High temperature plastic | PEEK, PTFE |
Frequently asked questions
How do I choose a material for a machined part?
In four steps: what the part touches, what load and temperature it sees, what finish it needs, and what quantity you are ordering. The environment and the temperature eliminate most candidates before price is considered.
Is aluminium or stainless steel better?
Aluminium is lighter, cheaper and easier to machine, and it anodizes; stainless is stronger, corrosion resistant without a coating, and weldable. For a bracket in dry conditions, aluminium. For a part in water, food or chemicals, stainless.
What is the cheapest material that still machines well?
For metal, 1045 carbon steel or 1215 free-cutting steel. For plastic, POM or ABS. Both machine fast, which matters more than the bar price at low quantity.
Why not use 303 stainless for a welded part?
Because 303 contains sulphur to make it free-machining, and the sulphur causes weld cracking. A welded stainless part should be 304 or 316L, which machine less easily and weld reliably.
When does material price start to matter more than machining?
Above roughly a few thousand pieces. Below that, setup and cycle time dominate the price, so choose the material that machines fastest rather than the one with the lowest price per kilogram.
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