How to Choose the Right Material for Your CNC Machined Parts
A practical guide to selecting between aluminum, steel, stainless, and engineering plastics for CNC machining — weighing strength, cost, weight, and finish.
Choosing the right material is one of the highest-leverage decisions you make before a part is ever cut. It drives cost, lead time, weight, strength, and how the part looks and lasts. Here is how we think about it when a customer sends us a drawing.
Start with the function, not the material
Before naming a material, get clear on what the part has to do:
- Loads: Is it structural, or just a cover? What forces does it see?
- Environment: Indoor, outdoor, marine, high temperature, chemical contact?
- Weight target: Does every gram matter (aerospace, robotics) or not?
- Finish & appearance: Cosmetic, or purely functional?
- Budget & volume: Prototype, small batch, or ongoing production?
Once those are clear, the material almost picks itself.
The four families we machine most
Aluminum (6061, 7075, 2024)
The default choice for most prototypes and many production parts. It’s lightweight, machines quickly (which lowers cost), and anodizes well for corrosion resistance and color.
- 6061-T6 — the all-rounder: good strength, great machinability, weldable.
- 7075-T6 — much higher strength, used in aerospace; costs more.
Steel (1045, 4140)
When you need strength and stiffness at lower cost than stainless, carbon and alloy steels are excellent — shafts, gears, tooling. They need plating or coating to resist corrosion.
Stainless steel (303, 304, 316)
Corrosion resistance and a premium look, at the cost of slower machining. 316/316L is the choice for medical and marine parts.
Engineering plastics (POM, PEEK, ABS, Nylon)
Light, electrically insulating, and self-lubricating in the case of POM (Delrin). PEEK handles high temperatures. Great for wear parts, insulators, and lightweight housings.
A quick decision shortcut
| If you need… | Consider |
|---|---|
| Lowest cost prototype | Aluminum 6061 |
| Maximum strength-to-weight | Aluminum 7075 or titanium |
| Corrosion resistance + looks | Stainless 304/316 |
| High strength, low cost | Alloy steel 4140 |
| Electrical insulation / light weight | POM or PEEK |
When in doubt, ask for a DFM review
The fastest way to avoid an expensive mistake is to send us your drawing or CAD model early. We’ll suggest a material and any small geometry changes that lower cost without changing function — before anything is cut.
Ready to get started? Request a quote and attach your files.