CNC Machining Materials: Metals, Grades and Selection
Meco machines several metal families and plastics daily in-house with no minimum order quantity.
What Materials Are Used in CNC Machining
CNC machining materials split into two groups. Metals which are able to hold tight tolerances at almost any batch size and plastic which trades stiffness for a lighter weight and lower cost per part.
This page lists the grades we actually run, not every grade that exists. For the machining processes themselves, see the CNC machining hub. For grades used in other processes, see the materials hub.
Metals
8 Families
Aluminum, carbon steel, alloy steel, stainless, brass, bronze, copper and titanium.
Plastics
9 Core Resins
Plus 50+ further grades, including glass and mineral filled compounds.
Standard Tolerance
±0.01 mm
ISO 2768. CMM verified to ±0.002 mm on critical features.
Documentation
EN 10204 3.1
Mill certificates, CoA, RoHS and REACH on request.
Swipe for all four
CNC Machining Materials by Metal Family
These are the metal grades we cut as routine production, and how each one behaves under a cutter.
| Metal | Grades We Run | Machinability | Typical CNC Parts |
|---|---|---|---|
| Aluminum | 6061, 6063, 6082, 7075, 5052, 2024 | Excellent. Fastest cutting speeds and longest tool life of any structural metal we run | Brackets, heat sinks, enclosures, manifolds |
| Carbon Steel | 1020, 1035, 1045 | Good. Low cost, predictable, general purpose | Shafts, pins, levers, fixture plates |
| Alloy Steel | 4140, 4340, 42CrMo, 52100 (GCr15), 40Cr, 12L14, 1215, 1144 | Fair to excellent. 4140, 4340 and 42CrMo need rigid setups and slower feeds; 12L14, 1215 and 1144 are free-cutting grades built for high speed turning | Gears, structural pins, high strength shafts, precision turned fittings, bearing races (52100) |
| Stainless Steel | 303, 304, 304L, 316, 316L, 420, 440, 430, 17-4PH, 2205, 2207 | Fair to difficult. Work hardens quickly and generates heat at the cutting edge; duplex grades 2205 and 2207 run slower still and need sharper tooling | Valve bodies, medical components, fasteners, cutting tool and blade parts (420, 440), marine and high corrosion fittings (2205, 2207) |
| Brass | C36000, C37700, C46400, C48500 | Excellent. Free machining alloys, especially C36000 | Fittings, valve stems, electrical terminals, marine hardware (C48500 naval brass) |
| Bronze | C63000 (QAl10-4-4), C93200 (SAE 660), C95400 | Good. Low friction under the tool, stable chip formation | Bushings, bearings, wear parts |
| Copper | C10100 (TU1), C12200 (TP2), C11000 (T2) | Good, but gummy chip formation needs sharp tooling | Busbars, connectors, electrical contacts |
| Titanium | Grade 2/TA2 and Grade 5/TC4 (Ti-6Al-4V) | Difficult. Low thermal conductivity concentrates heat at the tool tip | Aerospace fittings, medical implants and instruments |
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Aluminum and brass remove the most cost from a machining program, because higher cutting speeds and longer tool life bring cycle time down. Free-cutting steels such as 12L14, 1215 and 1144 do the same job for high volume turned parts. For a side by side property comparison, read aluminum vs brass vs titanium.
CNC Machining Materials by Plastic Resin
Machined plastic behaves differently from molded plastic. There is no shrinkage to design around, but stiffness, heat and moisture still shape the result.
| Resin | Chosen For | CNC Machining Notes |
|---|---|---|
| ABS | Low cost, stiff enough for fixtures and jigs | Can deflect under heavy cutting force on thin walls, keep passes light |
| PC | Impact strength, optical clarity | Notch sensitive, avoid sharp internal corners in the toolpath |
| PA (Nylon) | Wear resistance and toughness | Absorbs moisture after machining, final size can drift if not sealed |
| POM (Acetal) | Low friction, dimensional stability | Machines cleanly with a good finish, the easiest plastic on this list to hold tolerance in |
| PP | Chemical resistance, low cost | Low stiffness, prone to chatter on thin or unsupported sections |
| PE | Toughness, chemical resistance | Soft and gummy, needs sharp tooling to avoid smearing the surface |
| PEEK | High temperature and chemical service | Machines well and holds a fine finish, but is the highest material cost on this list by a wide margin |
| TPU | Flexibility, abrasion resistance | Soft materials deflect away from the cutter, best held with light finishing passes |
| UHMW-PE | Extremely high wear and impact resistance, low friction, self-lubricating | Machines well from extruded bar or sheet stock, but is prone to creep under sustained load and has limited heat and UV resistance, so avoid it in outdoor or elevated temperature duty |
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How to Choose a CNC Machining Material
Start with your nonnegotiable: weight, strength, corrosion, temperature, or cost. That one constraint eliminates most options before price.
6061 aluminum is the default for machined parts: fast to cut, good tolerance, low cost. Use 7075 or 2024 only when you truly need higher strengthtoweight. For high volume turned fittings where every second of cycle time matters, free-cutting steels such as 12L14, 1215 and 1144 outperform standard carbon steel on tool life and finish.
For corrosion, salt, or sterilization, choose 316 stainless or anodized 6061 over coated aluminum. Where the environment is harsher still, saltwater immersion or continuous high corrosion duty, duplex stainless 2205 or 2207, or naval brass C48500, outlast standard 316 stainless. For high heat or aggressive chemicals, PEEK is the plastic to look at despite its cost.
| If Your Priority Is | Look At | Why |
|---|---|---|
| Lowest cost, fastest turnaround | Aluminum 6061 | Cuts fast, holds tolerance, widest stock availability |
| Highest strength to weight | Aluminum 7075 or 2024 | Aerospace grade strength, slower cycle time than 6061 |
| High volume turned fittings | Free-cutting steel 12L14, 1215 or 1144 | Chips break cleanly at higher speeds, cutting cycle time and tool wear |
| Corrosion or sterilization resistance | Stainless 316 or 17-4PH | Holds up where anodized aluminum eventually fails |
| Saltwater or high corrosion duty | Duplex stainless 2205 or 2207, or naval brass C48500 | Outlasts standard 316 stainless or brass in continuous marine exposure |
| Fine detail, thin sections | Brass C36000 | Free machining alloy, crisp edges, minimal burring |
| Low friction, wear parts | POM (Acetal) or bronze | Both run without lubrication in sliding contact |
| High heat or chemical exposure | PEEK | Outperforms metal on chemical resistance at a fraction of the weight |
| Extreme strength to weight, aerospace or medical | Titanium Grade 5/TC4 | Highest cost and slowest cycle time, justified only where nothing else qualifies |
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What CNC Machining Will Hold, Regardless of Material
The grade changes cycle time and cost, but not the tolerance a well set up CNC program can hold. These figures apply across the metal and plastic grades above.
| Metric | Meco Figure |
|---|---|
| Standard tolerance | ±0.01 mm, to ISO 2768 |
| CMM verified tolerance | ±0.002 mm on critical features |
| Ideal batch size | 1 to 10,000 pieces, no minimum order quantity |
| Standard lead time | 1 to 3 weeks from released drawing |
| Quote turnaround | Under 24 hours, with DFM feedback included |
Where one feature needs tighter than a material naturally allows in one pass, we still hold it on the same setup rather than adding a second operation. For tolerance classes on drawings, see how to choose CNC machining tolerances.
Proving the Grade Is What We Said It Is
A grade claim is worth what the paperwork behind it is worth. Every shipment can carry the documents your incoming inspection will ask for.
Mill Certificates
Material certificates to EN 10204 3.1 and certificates of analysis, tied to the lot that made your parts.
Full Lot Traceability
Tracking from incoming raw material through machining and finishing, with a complete audit trail.
REACH and RoHS
Compliance documentation at both material and finished part level, plus conflict minerals reporting.
Quality Process Documentation
PPAP packages, first article inspection reports and CMM results, available on request for machined parts.
Swipe for all four
CNC Machining Materials FAQ
What materials are used in CNC machining?
CNC machining runs on metals including aluminum, carbon steel, alloy steel, stainless steel, brass, bronze, copper and titanium, plus engineering plastics such as nylon, POM, PEEK, ABS and UHMW-PE. Aluminum makes up the largest share of parts, because it cuts fast and holds tolerance without much tool wear.
Which metal is easiest to machine?
Aluminum 6061 and free machining brass grades like C36000 are the easiest metals to cut. Both allow higher speeds, longer tool life and a good surface finish straight off the tool. Titanium and hardened alloy steel sit at the other end, needing slower feeds and more frequent tool changes.
What is the difference between 6061 and 7075 aluminum for machining?
6061 machines faster and costs less, and it covers most general purpose parts. 7075 is stronger and better suited to aerospace grade, high stress applications, but it cuts slower and wears tooling faster, so it costs more per part even before material price is added.
What are free-machining steels, and which grades do you run?
Free-machining steels contain small additions of sulfur or lead that break chips cleanly at higher cutting speeds. We run 12L14, 1215 and 1144 for high volume turned fittings, alongside 40Cr and 52100, the bearing grade GB equivalent of GCr15, for hardened, wear resistant components such as bearing races.
Can stainless steel be CNC machined?
Yes. We machine 303, 304, 304L, 316, 316L, 420, 440, 430 and 17-4PH stainless grades, plus duplex stainless 2205 and 2207 for higher strength or corrosion duty. Stainless work hardens as it is cut, so it needs sharp tooling, steady feeds and more careful programming than carbon steel, which is why it costs more per part to machine even at the same tolerance.
Which grades hold up in saltwater or marine environments?
Duplex stainless 2205 and 2207, naval brass C48500, and aluminum bronze C63000 all outperform standard 316 stainless or brass in continuous saltwater exposure. We machine naval brass into marine hardware such as yacht lighting housings.
What plastics can be CNC machined?
ABS, PC, nylon, POM, PP, PE, PEEK, TPU and UHMW-PE can all be machined. POM machines the most cleanly of the group and holds the tightest tolerance. UHMW-PE offers the best wear and impact resistance but creeps under sustained load, and PEEK costs the most but survives heat and chemicals that would attack the others.
What tolerance can CNC machining hold?
Our standard is ±0.01 mm to ISO 2768, verified on CMM to ±0.002 mm on critical features. This applies across the metals and plastics on this page, though softer plastics need lighter finishing passes to hold the same number that a metal reaches easily.
Is titanium hard to machine?
Yes. Titanium's low thermal conductivity keeps cutting heat concentrated at the tool rather than carrying it away in the chip, which shortens tool life and slows the cut. We machine Grade 2/TA2 and Grade 5/TC4 (Ti-6Al-4V) titanium, mainly for aerospace and medical parts where nothing else qualifies.
Do you provide material certificates for machined parts?
Yes. Mill certificates to EN 10204 3.1, certificates of analysis, REACH and RoHS documentation, conflict minerals reporting, PPAP packages, first article inspection reports and CMM results are all available on request, with lot traceability from raw material to finished part.
How to Get a Material Recommendation
STEP or IGES plus a 2D drawing. Tell us load, operating temperature, finish and annual volume through the quote form.
Our engineers confirm the grade suits the geometry, flag tool access or thin wall issues, and say where a cheaper grade would perform the same.
Itemised piece price, the tolerance we will hold in that material, and one costed alternative where the choice is worth comparing.
Guides Behind These Material Choices
Three reads that go deeper into grade selection, tolerance and cost.
Best Materials for CNC Machining
Aluminum, steel, titanium, brass, PEEK and Delrin compared on machinability, cost and best use.
Read the guide →
Aluminum vs Brass vs Titanium
Hardness, density, strength, machinability and cost, in grade specific tables.
Read the guide →
How to Choose CNC Machining Tolerances
ISO 2768 tolerance classes explained, and when to call out a tighter feature.
Read the guide →Swipe for all three guides
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