Choosing the Best CNC Machining Materials

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.

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.