Few decisions carry more weight than selecting the right CNC machining materials for your project. The right choice ensures your parts perform reliably in their intended application, meet budget requirements, and can be produced efficiently.
At Approved Machining, we guide customers through this process every day, helping them balance performance, cost, and manufacturability. Whether you’re designing a prototype or planning a production run, understanding how to weigh strength, cost, and machinability is essential to making informed choices.
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Why Strength Is the First Question
When customers first approach our machine shop, their initial concern is almost always strength. Will the part withstand the loads, stresses, and environmental conditions it will encounter? For structural parts, the ability to resist high forces is critical. For cosmetic parts, the material still needs to endure wear, handling, or exposure without degrading.
Strength, however, isn’t the only factor. Customers often assume that the strongest available CNC machining materials, like titanium or hardened steel, are always the best choice. In reality, choosing an ultra-strong material can result in over-engineering. While titanium boasts an incredible strength-to-weight ratio, it’s difficult to machine, costly, and often unnecessary for many applications. An aluminum alloy like 6061 can often meet strength requirements at a fraction of the cost and machining time.
Balancing Cost With Performance
Once strength is evaluated, the conversation naturally shifts to cost. Material budgets can make or break a project, particularly when producing prototypes or small batches. Many customers are surprised to learn that the cheapest raw material doesn’t always yield the lowest part cost. For example, mild steel bar stock is inexpensive, but its fair machinability and need for finishing, such as painting or plating, often drive up the overall expense compared to aluminum.
This is where our expertise at Approved Machining provides real value. We help customers analyze not just the raw stock price, but the total cost of machining, finishing, and secondary processes. Aluminum 6061 is one of the most budget-friendly metals because it is both affordable and highly machinable. Brass, while more expensive as raw stock, can also save money because it machines quickly and cleanly, lowering labor and tooling costs.
On the plastics side, ABS and Delrin are two of the most cost-effective options. They machine beautifully, produce stable parts, and often don’t require finishing. For prototypes or lightweight applications, these materials keep costs under control without sacrificing performance.
Why Machinability Matters
Machinability is the third pillar of material selection and often the most underestimated. Even if a material has the right strength and a manageable price point, poor machinability can extend lead times, increase tool wear, and raise costs dramatically. For prototyping in particular, machinability can make the difference between getting a part in days versus weeks.
Take titanium or Inconel, for example. Both are incredibly strong and used in demanding industries like aerospace, but they are notoriously difficult to machine. Cutting speeds must be slow, specialized tooling is required, and heat buildup becomes a major challenge. By contrast, aluminum alloys or plastics like Delrin and ABS allow our team to machine parts quickly, efficiently, and with excellent dimensional accuracy.
For customers seeking quick turnaround, choosing CNC machining materials that balance machinability with required performance is crucial. We utilize our precision machining expertise to help customers align material choice with their project priorities.
Common Misconceptions About Material Selection
Over the years, our team has guided countless engineers and buyers through the material selection process. Along the way, we often encounter misconceptions:
- “Stronger is always better.” Not true! Over-engineering can waste time and money.
- “Stainless steel doesn’t rust.” Stainless is resistant, not immune, to corrosion; grade and environment matter.
- “All aluminum grades are basically the same.” In reality, 5052, 6061, and 7075 differ significantly in machinability, strength, and corrosion resistance.
- “Plastics aren’t strong enough.” Engineering plastics like Nylon, Ultem, or Delrin can be exceptionally strong and stable.
- “Machinability doesn’t matter if the design is right.” Difficult-to-machine materials can drive up costs even with good designs.
- “Cheaper raw material means cheaper parts.” Total cost depends on machining efficiency, secondary processes, and finishing, not just raw stock price.
By addressing these misconceptions, we help customers make smarter, more efficient choices.
Material & Grade | Relative Strength | Relative Cost | Machinability | Notable Pros | Notable Cons | Common Uses |
| Aluminum 6061 | Medium | Low | Excellent | Affordable, corrosion resistant, easy to machine | Not as strong as other alloys | Prototypes, housings, brackets |
| Aluminum 7075 | High | Medium-High | Good | Very strong, lightweight | Less corrosion resistant, more expensive | Aerospace, defense, high-performance parts |
| Stainless Steel 304 | High | Medium | Fair | Strong, corrosion resistant, widely available | Work hardens, slower machining | Food processing, medical, industrial parts |
| Stainless Steel 316 | High | High | Fair | Superior corrosion resistance (marine/chemical) | Expensive, tough to machine | Marine hardware, medical instruments |
| Carbon Steel 1018 | Medium-High | Low | Good | Low-cost raw stock, weldable, strong | Needs finishing to resist rust | Shafts, structural parts, industrial equipment |
| Brass | Medium | Medium | Excellent | Very machinable, stable, corrosion resistant | Heavier, more expensive than aluminum | Fittings, valves, electrical connectors |
| Titanium Ti-6Al-4V | Very High | Very High | Poor | Outstanding strength-to-weight ratio, biocompatible | Expensive raw stock, slow machining, tool wear | Aerospace, defense, implants |
| Inconel (Superalloy) | Very High | Very High | Very Poor | Extreme heat/corrosion resistance | Extremely expensive and slow to machine | Turbines, jet engines, energy industry |
| Copper | Medium | High | Poor | Excellent conductivity | Expensive, sticky to machine | Electrical and thermal components |
| ABS | Low | Low | Excellent | Cheap, easy to machine, stable for prototyping | Lower strength, poor heat resistance | Enclosures, fixtures, prototypes |
| Delrin (Acetal/POM) | Medium | Low-Medium | Excellent | Strong, low friction, great machinability | Not as heat resistant as some plastics | Gears, bushings, jigs, fixtures |
| Nylon | Medium | Low-Medium | Good | Wear-resistant, impact resistant | Moisture absorption affects stability | Bearings, insulators, wear parts |
| Ultem (PEI) | High | High | Fair | Heat resistant, strong, good electrical insulation | Expensive, slower to machine | Aerospace, electronics, medical |
| PTFE (Teflon) | Low | High | Poor | Chemical resistant, excellent insulator | Soft, gummy machining, dimensional instability | Seals, gaskets, chemical components |
| PEEK | High | Very High | Fair | Extreme performance, biocompatible | Very expensive raw stock | Aerospace, implants, high-performance engineering |
Metals and Plastics We Machine Most Often
At our shop, we regularly work with a broad range of metals and plastics. Aluminum 6061 and 7075 are customer favorites due to their balance of strength, weight, and machinability. Stainless steels 304 and 316 are common for medical, food, and marine applications, while carbon steels and brass remain strong choices for industrial parts and fittings. Titanium is less frequent, but critical when aerospace or defense projects demand it.
On the plastics side, Delrin, Nylon, Ultem, ABS, and PTFE are regularly machined. These materials deliver the dimensional stability, strength, and specialty properties, such as chemical resistance or electrical insulation, that certain applications demand.
Helping Customers Make the Right Choice
For those unsure about which CNC machining materials to choose, our process is straightforward but thorough. We begin by asking the right questions: What function does the part serve? What environment will it face? What are the project priorities? From there, we recommend materials that strike the right balance.
At Approved Machining, our mission is always to deliver parts that perform as intended, while saving customers time and money. By carefully considering strength, cost, and machinability, we ensure every project starts with the right foundation: the right material. Contact us today to see how we can help with your next project.
