CNC Milling Materials Compared: Aluminum, Stainless Steel, Titanium, and Engineering Plastics (2026)

The first step in using CNC milling to manufacture a part is selecting the correct CNC milling materials. The materials that is selected not only defines how well the manufactured part will meet the performance requirements. But it also has a big influence on budget, lead time and the overall success of the CNC machined part. 

Selecting the incorrect CNC milling material will create an additional expense, may render the part impossible to manufacture within the required tolerance or may cause the part to fail in use. The four major CNC milling material categories are included in the CNC milling companies located in China - aluminum alloys, stainless steel grades, titanium alloyed materials and engineering plastics.

This guide covers the four major CNC milling material categories available from Chinese CNC factories - aluminum alloys, stainless steel grades, titanium alloys, and engineering plastics, with selection criteria, machining considerations, and cost trade-offs for each.

Key Takeaways

• Aluminum is the most commonly CNC milled metal globally; it machines faster, costs less per kilogram, and produces less tool wear than any other structural metal.
• 6061-T6 is the correct default for most aluminum parts; 7075-T6 applies where higher strength is needed and the cost premium is justified by the application.
• Stainless steel grades 304 and 316 are not interchangeable: 316 is required where salt water or chemical exposure is present; 304 covers most indoor and structural applications.
• Titanium costs 3 to 5 times more to machine than aluminum: it is the right choice where weight, strength, and corrosion resistance are all required at once; it is the wrong choice where only one of those conditions applies.
• Engineering plastics are not a fallback option: PEEK, POM, and Nylon outperform metals on weight, chemical resistance, and cost in a wide range of applications.
• Material choice directly affects which surface finishes are possible: anodizing works on aluminum; passivation applies to stainless steel; titanium takes a different anodizing process.
• Specifying the wrong material grade, not just the wrong material category, is one of the most common causes of unnecessary cost increases on CNC milled parts.

How to Choose a CNC Machining Material?

Five factors determine which material category and grade is right for a given part. Working through these in order eliminates most wrong choices before a single grade is evaluated.

Decision Factor	The Question to Answer
Strength requirement	What load does the part carry? Does it need to resist impact, pulling force, or repeated stress?
Weight constraint	Is the part weight-sensitive? Does the assembly have a target weight budget?
Environment	Will the part be exposed to moisture, salt, chemicals, or high temperatures in service?
Material machinability	How complex is the geometry? How tight are the tolerances? How large is the production run?
Cost per finished part	What is the total budget including material, machining time, finishing, and inspection?

What Makes Aluminum the Most Commonly CNC Milled Metal?

The machining aluminum market was valued at USD 34.10 billion in 2023 and is projected to reach USD 57.28 billion by 2031 at a CAGR of 6.78%, driven by demand across aerospace, automotive, and industrial manufacturing. Aluminum dominates CNC milling because it machines faster than any other structural metal, produces less tool wear, and costs between $5–$15 per kilogram in raw stock, a fraction of titanium's $30–$100 per kilogram.

Aluminum is also the most forgiving material to specify. It holds tight tolerances reliably, accepts a wide range of surface finishes, and is available in every stock form, bar, plate, tube, and sheet, from verified suppliers globally. If a drawing specifies "aluminum" without a grade, most factories default to 6061-T6.

Aluminum Grade Comparison

Grade	Strength	Machinability	Corrosion Resistance	Cost vs 6061	Best For
6061-T6	Medium-high	Excellent	Good	Baseline	General structural parts, enclosures, brackets, frames
7075-T6	Very high	Good	Moderate	20–30% higher	High-load brackets, aerospace structures, competition components
2024-T3	High	Good	Poor (needs coating)	15–25% higher	Aerospace panels, parts under repeated stress
5052-H32	Medium	Very good	Excellent	Similar to 6061	Marine components, fuel tanks, sheet-form parts
6082-T6	Medium-high	Excellent	Good	Similar to 6061	Structural profiles, marine frameworks

6061-T6 is the correct default for the majority of CNC milled aluminum parts. It machines cleanly, holds tight tolerances, accepts anodizing evenly, and is the most widely available aluminum grade globally. Use it unless the design specifically requires something it cannot deliver.

7075-T6 applies where strength is the primary requirement and the 20–30% cost premium is justified. It is harder to machine than 6061 and its corrosion resistance is lower, so a surface coating or anodizing is usually required. Using 7075-T6 on an enclosure or bracket that 6061-T6 would handle adds cost with no functional benefit.

For a verified shortlist of factories with documented aluminum machining capability, best CNC milling factories in China provides a qualified starting point.

What Surface Finish Should You Use on Aluminum CNC Parts?

When Do You Need Stainless Steel For CNC Parts Instead of Aluminum?

Stainless steel is the right choice when a part needs to resist corrosion and carry meaningful structural load, conditions where aluminum falls short or where operating temperatures exceed aluminum's working range. It machines slower than aluminum, produces more tool wear, and costs more per kilogram, but for the applications it is designed for, no other material matches its combination of strength, hardness, and corrosion resistance at its price point.

Round and cylindrical stainless steel features shafts, pins, fittings, and threaded components, are often more cost-effective to produce on a CNC turning machine than a milling center, particularly for high-volume runs. Complex flat and angled shapes use milling; round parts with tight diameter requirements use turning.

Stainless Steel Grade Comparison

Grade	Corrosion Resistance	Machinability	Strength	Cost vs 304	Best For
304	Good	Moderate	High	Baseline	Food equipment, indoor structural parts, general fabrication
316	Excellent - salt and chemical resistant	Moderate	High	20–30% higher	Marine, medical, chemical processing, outdoor exposure
17-4 PH	Good	Moderate - more difficult than 304	Very high - nearly double 304	40–60% higher	Aerospace fasteners, surgical tools, high-stress shafts
303	Good	Best machinability of all stainless grades	High	Similar to 304	High-volume turned parts, threaded inserts, fittings
416	Moderate	Excellent	High	Similar to 304	Shafts, gears, valves where ease of machining matters

304 vs 316 is the most common grade decision in stainless steel sourcing. 316 contains an additional element “molybdenum” that blocks the type of corrosion caused by salt water, chlorine, and many industrial chemicals. 304 does not have this resistance. For indoor applications, food contact surfaces, and general structural uses with no chemical or salt exposure, 304 is sufficient and 20–30% cheaper. For anything exposed to seawater, swimming pool environments, medical sterilization, or chemical processing, 316 is required.

17-4 PH is a heat-treated grade with nearly double the strength of 304 or 316, making it appropriate for aerospace fasteners, high-stress shafts, and surgical instruments. It carries a significant cost premium and should only be specified where its strength level is genuinely needed.

What Surface Finish Should You Use on Stainless Steel CNC Parts?

Finish	What It Does
Passivation	Cleans the surface to improve its natural rust resistance; standard for medical and food-grade parts; no effect on part dimensions
Electropolishing	Smooths the surface at a microscopic level for easier cleaning; used in pharmaceutical and food processing
Bead blast	Uniform matte finish; no dimensional impact
PVD coating	Hard, thin decorative and wear-resistant layer; used for consumer and surgical applications
Powder coating	Durable color and surface protection; requires surface preparation

Does Your Part Actually Need Titanium?

Titanium is the right material when a part must be both strong and light, and when operating conditions rule out aluminum. Titanium CNC machining costs 3–5× more than aluminum, driven by three factors: slow cutting speeds, specialist cutting tools that wear faster than standard tooling, and raw material cost of $30–$100 per kilogram against aluminum's $5–$15.

The most commonly machined titanium grade is Ti-6Al-4V, an alloy that accounts for approximately 50% of all titanium used in manufacturing globally. It offers a strength-to-weight ratio higher than most steels, excellent corrosion resistance including in salt water and body fluid environments, and a working temperature up to 300°C.

When Titanium Is Worth the Cost

Application	Why Titanium	Why Not Aluminum or Steel
Aerospace structural brackets	Weight savings at required strength	Aluminum lacks strength; steel is too heavy
Orthopedic implants	Compatible with the body, bonds directly with bone, resists body fluids	Stainless steel is heavier and less body-compatible
Marine hardware for deep water use	Resists salt water corrosion indefinitely	Stainless steel corrodes over time in deep salt immersion
High-performance exhaust components	Handles high heat and repeated heating and cooling at low weight	Aluminum cannot handle the temperature; steel is heavier
Dental and surgical instruments	Body-compatible, resists sterilization, light weight	Stainless is heavier; plastics lack the required strength

When to Use an Alternative Instead

If the part does not require all three of titanium's defining properties, light weight, high strength, and resistance to extreme conditions. At the same time, a less expensive material covers the requirement.

7075-T6 aluminum handles most strength and weight requirements at a fraction of the cost. 316 stainless steel handles the majority of chemical and marine environments at significantly lower machining cost. Titanium is only justified when the application cannot be met by either alternative.

Are Engineering Plastics a Viable Alternative to Metal?

The global engineering plastics market was valued at USD 121.77 billion in 2025 and is projected to reach USD 192.42 billion by 2030 at a CAGR of 9.5%, driven by growing use of plastics as direct replacements for metals across automotive, electronics, and medical device manufacturing. In the right applications, engineering plastics deliver better performance than metals on weight, chemical resistance, electrical insulation, and cost per part.

CNC milled plastic parts also outperform 3D printed plastic parts on dimensional accuracy, surface finish quality, and material consistency - particularly for tight-tolerance functional components. For a direct comparison of when each process produces the better outcome, see CNC machining vs 3D printing. Or watch the video below!

Engineering Plastics Grade Comparison

Material	Strength	Temperature Resistance	Chemical Resistance	Machinability	Cost vs Aluminum	Best For
PEEK	Very high	Up to 260°C	Excellent	Good	3–5× higher	Medical implants, aerospace brackets, chemical equipment
POM (Delrin)	High	Up to 120°C	Good	Excellent	40–60% lower	Gears, bushings, valve components, sliding parts
Nylon (PA6/PA66)	Medium-high	Up to 120°C	Good	Good	50–70% lower	Structural brackets, housings, wear pads
Polycarbonate	Medium	Up to 135°C	Moderate	Very good	50–60% lower	Transparent covers, electrical housings, light-duty brackets
PTFE	Low-medium	Up to 260°C	Outstanding	Good	2–3× higher	Seals, gaskets, parts in direct chemical contact
HDPE	Medium	Up to 80°C	Very good	Excellent	60–70% lower	Marine components, chemical storage, food contact parts

PEEK delivers mechanical strength, high temperature performance, and chemical resistance that matches or exceeds many metals - at a fraction of the weight. It costs more per kilogram than most metals but machines faster than titanium, and the finished part is significantly lighter. Medical implants, chemical processing components, and aerospace brackets where reducing weight is a priority are its primary applications.

POM (Delrin) is the most practical engineering plastic for mechanical components - gears, bushings, valve seats, and sliding guides. It machines to tight tolerances, holds dimensions well in humid environments, and produces clean surface finishes without extra finishing steps. For high-volume mechanical parts where metal is used by default but not functionally required, POM is typically the most cost-effective alternative.

Nylon is the most widely available engineering plastic - inexpensive, easy to machine, and suitable for a broad range of structural and housing applications. Its one limitation is moisture absorption, which causes small dimensional changes in high-humidity environments. Where dimensional stability in wet conditions matters, POM is the better choice.

How Do CNC Milling Materials Compare Across Strength, Cost, and Machinability?

Tensile strength = how much pulling force the material resists before breaking. Higher MPa means a stronger material.

Once the grade is confirmed from the table below, submit a material-specified drawing through Haizol's Quick RFQ to receive comparable quotes from verified factories within 12–24 hours.

Material	Machinability	Tensile Strength	Corrosion Resistance	Relative Cost	Primary Application
Aluminum 6061-T6	Excellent	310 MPa	Good	Low - baseline	General structural, enclosures, brackets
Aluminum 7075-T6	Good	572 MPa	Moderate	Low-medium	Aerospace, high-load structures
Stainless Steel 304	Moderate	515 MPa	Good	Medium	Food, indoor structural, general fabrication
Stainless Steel 316	Moderate	515 MPa	Excellent	Medium-high	Marine, medical, chemical processing
Stainless Steel 17-4 PH	Moderate-difficult	1,000+ MPa	Good	High	Aerospace fasteners, surgical instruments
Titanium Ti-6Al-4V	Difficult	950 MPa	Excellent	Very high	Aerospace, medical implants, marine
PEEK	Good	100 MPa	Excellent	High	Medical, chemical equipment, aerospace brackets
POM (Delrin)	Excellent	70 MPa	Good	Low-medium	Gears, bushings, mechanical components
Nylon PA66	Good	85 MPa	Good	Low	Housings, brackets, wear pads
Polycarbonate	Very good	65 MPa	Moderate	Low	Transparent covers, electrical housings

Surface Finishing Compatibility by CNC Milling Material

Surface Finish	What It Does	Aluminum	Stainless Steel	Titanium	Engineering Plastics
Anodizing	Adds a protective layer and color to the surface	Yes - standard	No	Yes - decorative colors only	No
Chromate conversion coating	Protects against corrosion while keeping the surface electrically conductive	Yes - aerospace standard	No	No	No
Passivation	Cleans the surface to improve its natural rust resistance	No	Yes - standard for food and medical parts	No	No
Electropolishing	Smooths the surface at a microscopic level for easier cleaning	No	Yes - pharmaceutical and food processing	No	No
Bead blast	Creates a uniform matte surface texture	Yes	Yes	Yes	Yes - selected plastics only
Powder coating	Applies a durable colored protective layer	Yes	Yes	Yes	Limited - requires extra surface preparation
PVD coating	Applies a very hard, thin decorative and wear-resistant layer	Yes	Yes	Yes	No
Painting	Applies color and surface protection	Yes	Yes	Yes	Yes - requires primer and preparation
As-machined	No secondary finishing - surface left as cut	Yes	Yes	Yes	Yes

CNC Milling Materials FAQ (2026)

What Is the Easiest Metal to CNC Mill?

Aluminum is the easiest metal to CNC mill. Cutting speeds for aluminum run 800–2,000 surface feet per minute (a measure of how fast the cutting tool moves across the material) - significantly faster than stainless steel at 200–400 and titanium at 60–100. Aluminum also produces less tool wear, clears cut material cleanly, and holds tight tolerances without the heat buildup that affects harder metals.

For most applications, 6061-T6 aluminum is the correct starting point unless the design requirements specifically call for a harder or more corrosion-resistant material.

What Is the Difference Between 6061 and 7075 Aluminum?

6061-T6 has a tensile strength of 310 MPa, sufficient for the majority of structural, enclosure, and bracket applications - and machines easily with excellent surface finish results. 7075-T6 has a tensile strength of 572 MPa, making it one of the strongest aluminum grades available, but it costs 20–30% more and requires more care in machining to achieve the same surface quality. Use 6061-T6 as the default and switch to 7075-T6 only when the load requirement genuinely demands the higher strength.

When Should I Use 316 Stainless Steel Instead of 304?

Use 316 when the part will be exposed to salt water, chlorine, or industrial chemicals in service. 316 contains an additional element - molybdenum - that blocks the type of corrosion caused by these environments. 304 does not have this resistance.

For indoor structural applications, food contact surfaces with no chemical exposure, and general fabrication, 304 is sufficient and costs 20–30% less. The decision is based entirely on the operating environment.

Is Titanium Worth the Extra Cost for CNC Milled Parts?

Titanium is worth the cost when a part genuinely needs light weight, high strength, and strong resistance to corrosion or heat all at the same time. Titanium machining costs 3–5× more than aluminum. If the part only needs strength - 7075-T6 aluminum or 17-4 PH stainless steel covers it. If it only needs corrosion resistance - 316 stainless handles it.

Titanium is justified when the application cannot be met by either alternative, as in aerospace structural parts, medical implants, and deep-water marine hardware.

Can Engineering Plastics Replace Metals in CNC Milled Parts?

Yes - in many applications, engineering plastics are the better choice. PEEK handles high temperatures and aggressive chemicals at a fraction of metal's weight. POM machines to tight tolerances and is the correct material for gears, bushings, and sliding components. Nylon covers a broad range of structural and housing applications at lower cost and weight than aluminum. Plastics are not suitable where temperatures exceed 260°C, where high-impact structural loading is required, or where metal hardness is functionally necessary.

How Does Material Choice Affect CNC Milling Cost?

Material affects cost in two ways: raw material price per kilogram and how long the part takes to machine. Aluminum has the lowest cost on both measures - inexpensive raw stock and fast cutting speeds. Stainless steel costs more per kilogram and machines at roughly one-quarter the speed of aluminum, increasing cycle time and tool wear.

Titanium's raw material costs up to 7× more than aluminum and machines at one-tenth the speed, making finished parts 3–5× more expensive. Engineering plastics vary - POM and Nylon are cheaper than aluminum and machine quickly; PEEK costs more per kilogram than most metals but machines faster than titanium.

Source CNC Milled Parts in Any Material From Verified China Factories

Engineering and procurement teams sourcing parts across aluminum, stainless steel, titanium, and engineering plastic specifications can access material-matched verified factories through Haizol's platform.

Submit a material-specified drawing and receive comparable quotes from verified factories within 12–24 hours.