The table below is a decision aid, not a substitute for project engineering. Tell us what the part must do, and specify an exact standard when chemistry or mechanical properties are controlled.
Common machining metals
| Material family | Why engineers choose it | Design notes |
|---|---|---|
| Aluminum | Low mass, good machinability, thermal conductivity and broad finish options | Alloy and temper affect strength, anodizing color and dimensional behavior |
| Stainless steel | Corrosion resistance, strength and clean appearance | Grade selection changes machinability, magnetism and corrosion performance |
| Carbon / alloy steel | Strength, wear resistance and economical stock | Plan corrosion protection and consider distortion from heat treatment |
| Brass / copper | Conductivity, corrosion behavior and machinability | Pure copper can be demanding to machine; alloy selection matters |
| Titanium | High strength-to-weight ratio and corrosion resistance | Higher tooling and cycle-time demands; use where performance justifies cost |
Engineering plastics
| Material family | Typical strengths | Watch for |
|---|---|---|
| Acetal / POM | Dimensional stability, low friction, good machinability | Grade, color and environmental requirements |
| Nylon / PA | Wear resistance and toughness | Moisture absorption can affect dimensions |
| PEEK | Temperature and chemical performance | Material cost and application-specific grade |
| Polycarbonate | Impact resistance and transparency potential | Stress cracking, tool marks and cosmetic expectations |
| PTFE | Chemical resistance and low friction | Softness, creep and dimensional measurement |
Surface finishes
A finish callout should state the controlling standard, color or appearance expectation, masked areas, critical dimensions after coating and whether cosmetic defects are acceptable.
As machined
Fastest route when tool marks are acceptable. Surface roughness must be specified where it affects sealing, wear or appearance.
Anodizing
Common for aluminum to improve corrosion and wear behavior or add color. Alloy, surface preparation and lot variation influence appearance.
Passivation
Used with suitable stainless steels to support corrosion resistance after machining. Specify the governing process standard.
Plating and coating
Nickel, zinc, powder coat and other systems require allowance for thickness, masking and thread fit.
How to specify a finish clearly
- Name the process and applicable standard.
- Define color, gloss or texture with an approved reference where appearance matters.
- Mark surfaces that must remain uncoated.
- State whether dimensions apply before or after finishing.
- Identify threaded, electrical-contact, sealing and bearing surfaces.