CNC Machining Materials Guide: Metals, Plastics & How to Choose the Right Material for Your Parts

Material selection is one of the most consequential decisions in any CNC machining project. Choose wrong, and you end up with parts that fail under load, corrode in the field, or cost twice what they should. Choose right, and you get components that perform exactly as designed — at the right weight, strength, and price point.

This guide covers every material we machine — metals and engineering plastics — along with practical guidance on how to match materials to your application.

Metal Materials

Metals remain the dominant material category in CNC machining, offering unmatched combinations of strength, hardness, thermal performance, and surface finish capability. We work with six core metal families, each with multiple alloy grades to suit different performance and budget requirements.

A Closer Look at Key Metal Families

Aluminum — The Workhorse

Aluminum is the most widely machined metal for good reason: it cuts fast, holds tight tolerances, and delivers an excellent strength-to-weight ratio at a competitive cost. We stock all major structural grades. 6061-T6 covers most general-purpose applications. 7075-T6 steps in when strength is paramount — common in aerospace brackets and high-load fixtures. 2024 offers outstanding fatigue resistance for cyclic-load environments, while 5052 excels in marine and corrosive settings. All aluminum grades can be anodized, hard-anodized, or powder coated post-machining.

Stainless Steel — Strength Meets Corrosion Resistance

Our stainless steel capability spans nine grades, from free-machining 303 and universal 304 to marine-grade 316L and precipitation-hardened 17-4PH. Stainless takes more machining time than aluminum — it's tougher on tooling and generates heat — but it's indispensable for medical devices, food processing equipment, chemical handling, and any application where corrosion resistance and mechanical strength must coexist. 17-4PH and 15-5PH are particularly popular with aerospace and defense clients who need high yield strength with good corrosion resistance.

Steel — Maximum Strength for Structural Applications

Carbon and alloy steels are the backbone of industrial machining. 1018 is a general-purpose low-carbon steel ideal for shafts, pins, and non-critical structural parts. 1045 provides increased strength for gears and couplings. The 4130 and 4140 chromoly grades are go-to materials for high-stress applications in motorsport, oil & gas, and heavy machinery — offering excellent toughness and hardenability. 4340 pushes further into high-impact territory, commonly used for aircraft landing gear components and power transmission shafts.

Brass & Copper — Precision Finish and Conductivity

Brass machines beautifully — it's one of the few materials where you can achieve mirror-like surface finishes without post-processing. C360 (free-machining brass) is a staple for fluid fittings, valve bodies, and threaded connectors. Our copper grades — C10100 (Oxygen-Free), C10200, and C11000 — are selected for applications where electrical or thermal conductivity is the primary requirement: bus bars, heat sinks, electrode contacts, and RF components.

Titanium — When Weight and Strength Both Matter

Titanium Grade 5 (Ti-6Al-4V) is the industry standard for parts that need to be lightweight, incredibly strong, and biocompatible. It's roughly 45% lighter than steel at comparable tensile strength. We machine titanium regularly for aerospace structural components, orthopedic implants, and high-performance motorsport parts. Titanium requires specialized tooling and controlled cutting parameters — our team has the experience to hold tight tolerances on this demanding material without compromising surface integrity.

Plastic Materials

Engineering plastics are a smart choice when weight reduction, electrical insulation, chemical resistance, or cost efficiency are priorities. We machine ten plastic materials across a wide performance spectrum — from everyday ABS to extreme-performance PEEK.

Choosing the Right Plastic

For general prototyping and functional enclosures, ABS and PC are cost-effective and easy to machine. When wear resistance and dimensional stability matter — gears, bushings, sliding components — POM (Delrin) is the standard choice. For chemical-exposed environments, PTFE, PP, and PVC offer excellent resistance without metal's weight or cost. PEEK sits at the top of the performance ladder: it handles temperatures up to 250°C, resists aggressive chemicals, and meets FDA and biocompatibility requirements for medical devices. HDPE and UHMW round out the lineup for high-wear, low-friction applications in food processing and material handling equipment.

How to Choose: A Practical Framework

When specifying a material, consider these four dimensions:

• Mechanical requirements — tensile strength, hardness, fatigue life, impact resistance
• Environmental exposure — temperature range, corrosion risk, chemical exposure, UV resistance
• Regulatory requirements — FDA, RoHS, REACH, AS9100, ISO 13485 certifications
• Budget — raw material cost vs. machining complexity vs. total lifecycle cost

If you're unsure which material fits your application, our engineering team provides free material consultation with every quote request. We've helped hundreds of clients across North America and Europe optimize their material choices — often reducing cost while improving performance or longevity.

→ Upload your drawing and let us recommend the optimal material for your project. Get a quote within 24 hours.