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CNC Machining Materials: Grades, Properties and Machinability
91 grades in 12 families, with EN, JIS and UNS equivalents, typical properties, how each one behaves on a 5-axis machine and the parts it is used for.
On this page
- Choose by requirement
- Aluminum alloys
- Stainless steels
- Carbon and alloy steels
- Tool steels
- Cast iron
- Titanium alloys
- Nickel and cobalt superalloys
- Copper, brass and bronze
- Magnesium alloys
- Special and refractory metals
- Engineering plastics
- Composites, laminates and ceramics
- Machinability compared
Property values are typical room temperature figures for the usual temper, rounded. Use them to pick a grade, not as design values. Equivalents across standards are close, not identical.
Choose by what the part has to do
Start from the requirement, then check the family table below for the grade, its equivalents and what it does to the price.
Say it once, on the RFQ
Name the grade, the temper or heat treat condition and the standard, for example 7075-T651 to AMS-QQ-A-250/12, 17-4 PH H1025 or Ti-6Al-4V ELI to ASTM F136. Add whether you need a material certificate. It is the fastest way to get matched with a shop that already runs it.
- Light and strong7075-T6, Ti-6Al-4V, magnesium AZ31B or ZK60A, CFRP
- General purpose, low cost6061-T6, 1018 or 1045 steel, 303 stainless, POM
- Corrosion and chemicals316L, duplex 2205, titanium Grade 2, Hastelloy C-276, PVDF, PTFE
- Heat above 300°CInconel 718 or 625, Ti-6242, 310 stainless, H13, Macor
- Hardness and wearD2, A2, 440C, 52100, 17-4 PH H900, nitrided 4140, PAI
- Electrical or thermal conductivityC110 or C101 copper, C145, C18150, 6061 aluminum
- Electrical insulationPEEK, PEI, G-10 / FR-4, PTFE, Macor, alumina
- Dimensional stability with temperatureInvar 36, Kovar, cast tooling plate, CF30 PEEK
- Implants and surgical useTi-6Al-4V ELI (F136), 316LVM (F138), CoCrMo (F1537), implant grade PEEK
- Food contact304 or 316L stainless, FDA compliant POM, UHMW-PE and PEEK
- Fastest machining, lowest piece priceC360 brass, 2011 or 6061 aluminum, 12L14 steel, POM
Aluminum alloys
The default material for 5-axis work. Light, stable, fast to cut and easy to anodize. Most prototypes and a large share of production parts start here.
| Grade | Equivalents | Typical properties | Machinability | Used for |
|---|---|---|---|---|
| 6061-T6 / T651 | EN AW-6061, JIS A6061, UNS A96061 | 2.70 g/cm³, tensile about 310 MPa, yield 275 MPa | Good | General purpose: brackets, housings, fixtures, frames. Anodizes and welds well. |
| 6082-T6 | EN AW-6082 (AlSi1MgMn) | 2.70 g/cm³, tensile about 310 MPa | Good | The common European structural grade, used where 6061 is in the US. |
| 7075-T6 / T651 | EN AW-7075, JIS A7075, UNS A97075 | 2.81 g/cm³, tensile about 570 MPa, yield 500 MPa | Excellent | High stress parts: aerospace fittings, motorsport, robot arms, molds for short runs. Not for welding. |
| 7050-T7451 | EN AW-7050, UNS A97050 | 2.83 g/cm³, tensile about 510 MPa | Excellent | Thick aerospace plate. Better toughness and stress corrosion resistance than 7075 in heavy sections. |
| 2024-T351 | EN AW-2024, JIS A2024, UNS A92024 | 2.78 g/cm³, tensile about 470 MPa | Good | Fatigue loaded aerospace structure. Poor corrosion resistance, usually anodized or chem filmed. |
| 2011-T3 | EN AW-2011, UNS A92011 | 2.83 g/cm³, tensile about 380 MPa | Excellent | Free-machining bar for lathe and Swiss work: fittings, screws, pins. |
| 5052-H32 | EN AW-5052, JIS A5052 | 2.68 g/cm³, tensile about 230 MPa | Fair | Marine and sheet metal parts, enclosures. Not heat treatable. |
| Cast tooling plate (for example MIC-6) | Cast and stress relieved Al-Mg plate | Tensile about 165 MPa, very flat and stable | Good | Base plates, vacuum fixtures, inspection plates where flatness matters more than strength. |
| A356-T6 and A380 / ADC12 castings | EN AC-42100, EN AC-46000 range | 2.68 to 2.74 g/cm³ | Good | Machining of sand and die cast housings: pumps, gearboxes, enclosures. Silicon wears tools faster. |
On the machine
- Cutting speeds of several hundred meters per minute with sharp polished carbide. Cycle time is short, so setup and programming are most of the price.
- Thin walls and large pockets move when stress is released. Thick plate in T651 or T7451 temper is stress relieved by stretching and moves less.
- Soft alloys such as 5052 and 1100 are gummy and build up on the edge. 2011 and 6262 are free-machining choices for turned parts.
- Tolerance to expect
- ±0.01 to ±0.025 mm is common, ±0.005 mm on selected features.
- Finishes that fit
- Anodizing Type II and III, chem film, bead blast, electroless nickel, powder coat.
- Read the guide
- 5-Axis CNC Machining Aluminum Parts: Grades, Tolerance and Cost
Stainless steels
Chosen for corrosion resistance, cleanliness and strength. Austenitic grades work harden, so the shop has to keep the tool cutting and never let it rub.
| Grade | Equivalents | Typical properties | Machinability | Used for |
|---|---|---|---|---|
| 303 | EN 1.4305, JIS SUS303, UNS S30300 | 8.0 g/cm³, tensile about 620 MPa | Good | Free-machining stainless for fittings, shafts and screws. Lower corrosion resistance, not for welding. |
| 304 / 304L | EN 1.4301 / 1.4307, JIS SUS304 / SUS304L | 8.0 g/cm³, tensile about 520 to 620 MPa | Fair | General corrosion resistance: food equipment, enclosures, brackets. |
| 316 / 316L | EN 1.4401 / 1.4404, JIS SUS316 / SUS316L | 8.0 g/cm³, tensile about 490 to 580 MPa | Fair | Molybdenum grade for chlorides: marine, pharma, semiconductor, medical (316LVM to ASTM F138). |
| 17-4 PH | EN 1.4542, JIS SUS630, UNS S17400 | 7.8 g/cm³, H900 tensile about 1,310 MPa, 40 to 47 HRC | Fair | High strength corrosion resistant parts: aerospace fittings, valve parts, pump shafts, surgical tools. |
| 15-5 PH | EN 1.4545, UNS S15500 | 7.8 g/cm³, similar strength to 17-4 PH | Fair | Aerospace version of 17-4 PH with better toughness across the grain. |
| 416 | EN 1.4005, JIS SUS416, UNS S41600 | 7.7 g/cm³, hardenable to about 35 to 40 HRC | Good | Free-machining martensitic grade for valve trim, shafts and fasteners. |
| 420 | EN 1.4021 / 1.4028, JIS SUS420J2 | 7.7 g/cm³, hardenable to about 50 HRC | Fair | Surgical instruments, cutting blades, plastic mold inserts. |
| 440C | EN 1.4125, JIS SUS440C, UNS S44004 | 7.7 g/cm³, hardenable to 58 to 60 HRC | Fair (annealed) | Bearings, valve balls and seats, wear parts. Finished by grinding after hardening. |
| Duplex 2205 | EN 1.4462, UNS S32205 / S31803 | 7.8 g/cm³, yield at least 450 MPa | Difficult | Oil and gas, chemical and desalination parts. About twice the yield strength of 316. |
| Super duplex 2507 | EN 1.4410, UNS S32750 | 7.8 g/cm³, yield at least 550 MPa | Difficult | Subsea and seawater service. Needs rigid setups and sharp tools. |
On the machine
- Cutting speed is roughly a third to a half of steel of the same hardness. Tool wear and heat drive the cycle time.
- Austenitic grades (304, 316) work harden. A dull tool or a dwell makes the next cut harder. Feed must stay constant.
- Precipitation hardening grades (17-4 PH, 15-5 PH) are machined in condition A or H1150, then aged. Aging shrinks the part slightly and predictably.
- Tolerance to expect
- ±0.01 to ±0.025 mm is common.
- Finishes that fit
- Passivation, electropolishing, bead blast, laser marking, PVD.
- Read the guide
- 5-Axis Machining Stainless Steel: Grades, Tolerances and Cost
Carbon and alloy steels
Cheap, strong and available everywhere. Alloy steels are heat treated to the strength the design needs, and they need a coating or oil against rust.
| Grade | Equivalents | Typical properties | Machinability | Used for |
|---|---|---|---|---|
| 1018 / 1020 | Close to EN C15E / C22E | 7.87 g/cm³, tensile about 440 MPa cold drawn | Good | Low carbon steel for brackets, spacers, fixtures and welded parts. |
| 1045 | EN C45 (1.0503), JIS S45C | 7.85 g/cm³, tensile about 570 to 630 MPa | Good | Medium carbon shafts, pins, gears. Can be induction hardened. |
| 12L14 | EN 11SMnPb30 (1.0718) | 7.87 g/cm³, tensile about 540 MPa | Excellent | High volume turned parts that are not welded or heat treated. |
| 4140 / 4140 pre-hard | EN 42CrMo4 (1.7225), JIS SCM440 | 7.85 g/cm³, pre-hard 28 to 32 HRC, tensile about 950 MPa | Good | Shafts, tooling, fixtures, hydraulic and oil field parts. |
| 4340 | Close to EN 34CrNiMo6 (1.6582) | 7.85 g/cm³, tensile 1,000 to 1,800 MPa after hardening | Fair | High strength landing gear parts, heavy shafts, gears. |
| 8620 | EN 20NiCrMo2-2 (1.6523), JIS SNCM220 | 7.85 g/cm³, case 58 to 62 HRC after carburizing | Good | Carburized gears, cams, pins and shafts. |
| 52100 | EN 100Cr6 (1.3505), JIS SUJ2 | 7.81 g/cm³, 60 to 64 HRC hardened | Fair (annealed) | Bearing rings, balls, precision shafts and gauges. |
| A36 / S355 plate | ASTM A36, EN S355J2 | 7.85 g/cm³, yield 250 / 355 MPa | Good | Weldments, machine frames and bases, machined after welding and stress relief. |
On the machine
- Free-machining grades (12L14, 1215) cut fastest and give the best finish on the lathe. They do not weld well.
- Pre-hardened 4140 at 28 to 32 HRC can be finished in one go without heat treatment afterwards. Harder parts are roughed soft, hardened, then ground or hard milled.
- Carburizing grades (8620, 9310) are machined soft, case hardened, then ground on the functional surfaces.
- Tolerance to expect
- ±0.01 to ±0.025 mm, tighter after grinding.
- Finishes that fit
- Black oxide, zinc and zinc-nickel plating, electroless nickel, nitriding, paint.
Tool steels
Made to be hardened. Used for molds, dies, punches, wear parts and fixtures. The heat treatment sequence decides the process route and the price as much as the grade does.
| Grade | Equivalents | Typical properties | Machinability | Used for |
|---|---|---|---|---|
| A2 | EN 1.2363, JIS SKD12 | 57 to 62 HRC, air hardening, low distortion | Fair (annealed) | Punches, forming dies, gauges, wear parts. |
| D2 | EN 1.2379, close to JIS SKD11 | 58 to 62 HRC, high wear resistance | Difficult (annealed) | Blanking and trimming dies, slitter knives, wear plates. |
| H13 | EN 1.2344, JIS SKD61 | 44 to 52 HRC, holds hardness when hot | Fair (annealed) | Die casting dies, extrusion tooling, hot forging dies, plastic molds. |
| O1 | EN 1.2510, close to JIS SKS3 | 57 to 62 HRC, oil hardening | Good (annealed) | Short run dies, gauges, knives, bushings. |
| S7 | Close to EN 1.2357 | 54 to 58 HRC, shock resistant | Fair (annealed) | Chisels, punches and parts under impact. |
| P20 / P20+Ni | EN 1.2311 / 1.2738 | Supplied pre-hardened at 28 to 34 HRC | Good | Plastic injection mold bases, cavities and cores, no heat treatment after machining. |
| 420 mold stainless | EN 1.2083 | 48 to 52 HRC, polishes to a mirror | Fair (annealed) | Medical and optical molds, corrosive plastics such as PVC. |
| M2 high speed steel | EN 1.3343, JIS SKH51 | 62 to 65 HRC | Difficult (annealed) | Cutting tools, punches, wear parts that run hot. |
On the machine
- Bought annealed, machined close to size, hardened in a vacuum furnace, then finished by grinding, hard milling or wire EDM.
- Hard milling with coated carbide or CBN can finish molds at 50 to 62 HRC directly, which removes the electrode and EDM step on many cavities.
- Leave 0.1 to 0.3 mm per side for finishing after hardening, more on large or thin parts that distort.
- Tolerance to expect
- ±0.005 to ±0.01 mm after grinding or wire EDM.
- Finishes that fit
- Ground, polished to mold finish (SPI A to D), nitrided, PVD coated.
- Read the guide
- 5-Axis Hard Milling of Tool Steel Above 50 HRC
5-Axis Mold Machining: Cores and Cavities vs EDM
Cast iron
Bought as a casting and machined to size. It damps vibration, wears well and is cheap in volume. Gray iron makes short chips and dust, ductile iron behaves more like steel.
| Grade | Equivalents | Typical properties | Machinability | Used for |
|---|---|---|---|---|
| Gray iron | EN-GJL-250, close to ASTM A48 Class 35 to 40, JIS FC250 | 7.2 g/cm³, tensile about 250 MPa, high damping | Good | Machine tool bases, pump housings, brake parts, manifolds. |
| Ductile iron | EN-GJS-450-10, close to ASTM A536 65-45-12, JIS FCD450 | 7.1 g/cm³, tensile about 450 MPa, elongation 10% | Good | Valve bodies, gearbox housings, hydraulic parts, crankshafts. |
| Compacted graphite iron (CGI) | EN-GJV-450 | 7.1 g/cm³, tensile about 450 MPa | Fair | Diesel engine blocks and heads. |
On the machine
- Gray iron is usually cut dry, so a shop needs good dust extraction. Coolant turns the graphite dust into a paste.
- The hard skin and sand inclusions on the casting surface wear tools fast on the first pass.
- Large castings are often stress relieved or aged before finish machining to keep them stable.
- Tolerance to expect
- ±0.01 to ±0.025 mm on machined faces.
- Finishes that fit
- Paint, black oxide, phosphate, rust preventive oil.
Titanium alloys
Half the weight of steel with similar strength, excellent corrosion resistance and accepted in the body. It conducts heat poorly, so the heat stays at the cutting edge and the cutting speed is low.
| Grade | Equivalents | Typical properties | Machinability | Used for |
|---|---|---|---|---|
| Grade 2 (commercially pure) | UNS R50400, EN 3.7035 | 4.51 g/cm³, tensile at least 345 MPa | Fair | Chemical process parts, heat exchangers, marine hardware. |
| Grade 4 (commercially pure) | UNS R50700, EN 3.7065 | 4.51 g/cm³, tensile at least 550 MPa | Fair | Dental implants and high strength CP parts. |
| Grade 5 (Ti-6Al-4V) | UNS R56400, EN 3.7165 | 4.43 g/cm³, tensile at least 895 MPa | Difficult | Aerospace brackets and fittings, motorsport, high performance bike and robot parts. |
| Grade 23 (Ti-6Al-4V ELI) | UNS R56401, ASTM F136 | 4.43 g/cm³, tensile at least 860 MPa | Difficult | Orthopedic and spinal implants, surgical instruments. |
| Ti-6Al-2Sn-4Zr-2Mo (Ti-6242) | UNS R54620 | 4.54 g/cm³, keeps strength to about 540°C | Difficult | Jet engine compressor parts and hot airframe structure. |
| Beta alloys (Ti-5553, Ti-10-2-3) | Near beta, aerospace specs | 4.6 to 4.7 g/cm³, tensile 1,100 to 1,300 MPa | Very difficult | Landing gear and highly loaded airframe parts. |
On the machine
- Thermal conductivity of Ti-6Al-4V is about 7 W/m·K, against about 167 W/m·K for 6061. Speeds are typically 40 to 80 m/min with high pressure coolant.
- Adaptive toolpaths, constant chip load and rigid workholding decide tool life. Chatter ruins both tools and surface.
- Fine titanium chips can ignite. Shops that run it regularly keep chips wet and the machine clean.
- Tolerance to expect
- ±0.01 to ±0.025 mm is common.
- Finishes that fit
- Bead blast, anodizing for titanium (AMS 2488), passivation, polishing.
- Read the guide
- 5-Axis Machining Titanium Parts: What Makes It Different
Nickel and cobalt superalloys
Keep their strength at temperatures where steel and titanium soften. The same property makes them hard on tools: they stay strong in the cutting zone and work harden quickly.
| Grade | Equivalents | Typical properties | Machinability | Used for |
|---|---|---|---|---|
| Inconel 718 | UNS N07718, EN 2.4668, AMS 5662 / 5663 | 8.19 g/cm³, aged tensile about 1,240 MPa or more | Very difficult | Turbine discs, shafts, casings, rocket and oil tool parts up to about 650°C. |
| Inconel 625 | UNS N06625, EN 2.4856 | 8.44 g/cm³, tensile about 830 to 1,030 MPa | Very difficult | Seawater, chemical and exhaust parts. Gummy, work hardens. |
| Hastelloy C-276 | UNS N10276, EN 2.4819 | 8.89 g/cm³, tensile about 750 MPa | Very difficult | Valves, pumps and fittings for acids and chlorides. |
| Monel 400 / K-500 | UNS N04400 / N05500, EN 2.4360 / 2.4375 | 8.8 g/cm³, K-500 aged above 1,000 MPa | Difficult | Marine shafts, pump and valve parts, seawater fasteners. |
| Waspaloy | UNS N07001, EN 2.4654 | 8.2 g/cm³, higher temperature service than 718 | Very difficult | Turbine discs, rings, seals and casings. |
| Cobalt chrome (CoCrMo) | ASTM F75 (cast), ASTM F1537 (wrought) | 8.3 g/cm³, tensile above 1,100 MPa (F1537) | Very difficult | Knee and hip implants, dental frameworks, wear surfaces. |
On the machine
- Carbide speeds of 20 to 50 m/min, ceramic inserts for roughing on some grades. Tool cost is a real part of the quote.
- Fewer shops take this work, so expect longer quote times and a narrower shortlist.
- Aged 718 is cut in the solution treated condition when possible, then aged, with allowance for small size change.
- Tolerance to expect
- ±0.025 mm is a safer target, tighter on selected features.
- Finishes that fit
- Passivation, abrasive blasting, grinding, EDM recast control.
- Read the guide
- Inconel 718 on 5-Axis Machines: What to Expect
Copper, brass and bronze
Copper is chosen for electrical and thermal conductivity, brass for fast machining and good looks, bronze for bearings and seawater. The family ranges from the easiest metal to cut to one of the stickiest.
| Grade | Equivalents | Typical properties | Machinability | Used for |
|---|---|---|---|---|
| C110 copper (ETP) | EN Cu-ETP (CW004A), JIS C1100 | 8.89 g/cm³, conductivity 100% IACS | Fair | Bus bars, electrical contacts, heat sinks. |
| C101 copper (OFE) | EN Cu-OFE (CW009A), JIS C1011 | 8.94 g/cm³, conductivity 101% IACS, very low oxygen | Fair | Vacuum and RF parts, accelerator and semiconductor parts. |
| C145 tellurium copper | EN CuTeP (CW118C) | 8.94 g/cm³, conductivity above 90% IACS | Good | Machined electrical connectors and contacts in volume. |
| C18150 chromium zirconium copper | EN CuCr1Zr (CW106C) | 8.89 g/cm³, conductivity about 80% IACS, hardened | Fair | Resistance welding electrodes and tips, mold inserts. |
| C17200 beryllium copper | EN CuBe2 (CW101C) | 8.25 g/cm³, tensile up to about 1,380 MPa after aging | Good | Springs, non-sparking tools, mold cores, connector contacts. |
| C360 free-cutting brass | EN CuZn39Pb3 (CW614N), JIS C3604 | 8.50 g/cm³, machinability rating 100 | Excellent | Fittings, valves, screws, instrument parts. |
| Lead-free brass | C69300, EN CuZn21Si3P (CW724R) | 8.3 g/cm³ | Good | Drinking water fittings where lead is restricted. |
| C932 bearing bronze | SAE 660, close to EN CuSn7Zn4Pb7-C | 8.9 g/cm³ | Excellent | Bushings, thrust washers, wear plates. |
| C954 aluminum bronze / C630 nickel aluminum bronze | EN CuAl10Fe3 / CuAl10Ni5Fe4 (CW307G) | 7.5 to 7.6 g/cm³, tensile about 590 to 690 MPa | Fair | Marine propeller parts, valve seats, gears, heavy duty bushings. |
| C510 phosphor bronze | EN CuSn5 (CW451K) | 8.86 g/cm³, good spring properties | Fair | Springs, bushings, electrical contacts. |
On the machine
- Free-cutting brass C360 is the reference for machinability (rating 100). Chips break short and finish is excellent.
- Pure copper is soft and gummy. It needs sharp polished tools, high rake and steady coolant to avoid burrs and smearing.
- Beryllium copper is safe as a solid, but machining dust and fumes must be controlled. Use a shop that already handles it.
- Tolerance to expect
- ±0.01 to ±0.025 mm, ±0.005 mm on brass turned parts.
- Finishes that fit
- Nickel, tin, silver or gold plating, passivation for brass, clear lacquer, polishing.
- Read the guide
- 5-Axis Machining Copper and Brass: Burrs and Finish
Magnesium alloys
The lightest structural metal, about two thirds the weight of aluminum. It cuts very fast with little tool wear, but fine chips and dust are a fire risk that the shop must manage.
| Grade | Equivalents | Typical properties | Machinability | Used for |
|---|---|---|---|---|
| AZ31B | EN MgAl3Zn1, ASTM B90 / B107 | 1.77 g/cm³, tensile about 260 MPa | Excellent | Plate and extrusions: camera and electronics housings, jigs, aerospace interior parts. |
| AZ91D | EN MC21120, die casting alloy | 1.81 g/cm³, tensile about 230 MPa | Excellent | Machining of die cast housings and covers. |
| ZK60A | ASTM B91 / B107 | 1.83 g/cm³, tensile about 340 MPa | Excellent | Forged and extruded parts with higher strength: wheels, bike and sporting parts. |
| WE43 | AMS 4427, EN MgY4RE3Zr | 1.84 g/cm³, holds strength at higher temperature | Excellent | Aerospace and motorsport gearbox housings, bioresorbable implant research. |
On the machine
- Cut dry or with oil based coolant. Water based coolant and fine magnesium chips release hydrogen.
- Keep chips coarse, the machine clean and a Class D extinguisher close. Ask whether the shop already runs magnesium.
- Corrodes quickly without protection, so parts are coated soon after machining.
- Tolerance to expect
- ±0.01 to ±0.025 mm.
- Finishes that fit
- Conversion coatings, anodizing for magnesium, paint and powder coat.
Special and refractory metals
Used for one property no common alloy offers: near zero thermal expansion, a glass-matching expansion, very high density or very high melting point.
| Grade | Equivalents | Typical properties | Machinability | Used for |
|---|---|---|---|---|
| Invar 36 | UNS K93600, EN 1.3912 | 8.05 g/cm³, expansion about 1.2 ppm/K near room temperature | Difficult | Optical benches, metrology frames, composite layup tools, satellite structure. |
| Kovar | UNS K94610, ASTM F15 | 8.36 g/cm³, expansion about 5 ppm/K, matched to glass | Difficult | Glass-to-metal seals, hermetic electronic packages, sensor housings. |
| Tungsten heavy alloy | ASTM B777 (W-Ni-Fe, W-Ni-Cu) | 17 to 18.5 g/cm³ | Fair | Counterweights, radiation shielding, collimators, vibration dampers. |
| Molybdenum and TZM | ASTM B387 | 10.2 g/cm³, melting point about 2,620°C | Fair | Furnace parts, semiconductor and glass melting parts, heat sinks. |
| Tantalum, niobium, zirconium | ASTM B365, B392, B551 | 6.5 to 16.6 g/cm³, high corrosion resistance | Difficult | Chemical process parts, superconducting RF cavities, implants and nuclear parts. |
On the machine
- Invar and Kovar are gummy like austenitic stainless. Stress relief between roughing and finishing keeps the low expansion part stable.
- Tungsten heavy alloy and molybdenum are abrasive and brittle at the edges. Carbide tools and light finishing cuts.
- Tantalum, niobium and zirconium smear and gall. Few shops have the experience, so expect a short shortlist.
- Tolerance to expect
- ±0.01 to ±0.025 mm.
- Finishes that fit
- Mostly as machined, nickel or gold plating on Kovar, passivation.
Engineering plastics
Light, insulating, chemically resistant and often cheaper to machine than metal. They also expand ten times more than steel with heat, some absorb water and all of them relax after machining. Tolerances need to respect that.
| Grade | Equivalents | Typical properties | Machinability | Used for |
|---|---|---|---|---|
| POM-C acetal copolymer | Generic acetal, for example Hostaform, Tecaform AH | 1.41 g/cm³, up to about 100°C | Excellent | Gears, bushings, rollers, food machinery parts. No centerline porosity. |
| POM-H acetal homopolymer (Delrin) | Delrin 150 and similar | 1.42 g/cm³, stiffer than POM-C | Excellent | Precision gears, snap fits, wear parts. Thick bar can have centerline porosity. |
| PEEK | Unfilled, 30% glass (GF30), 30% carbon (CF30), implant grade | 1.30 g/cm³, up to 250°C continuous | Good | Semiconductor wafer handling, aerospace clips, valve seats, medical instruments and implants. |
| PEI (Ultem 1000 / 2300) | Unfilled and 30% glass filled | 1.27 g/cm³, up to about 170°C, flame retardant | Good | Electrical insulators, sterilizable medical parts, test sockets. |
| PAI (Torlon 4203) | Polyamide-imide | 1.42 g/cm³, up to about 250°C, very stiff | Fair | Bearings and seals in hot or high load service, test sockets. |
| PI (Vespel SP-1) | Polyimide | 1.43 g/cm³, up to about 290°C | Fair | Jet engine bushings, vacuum and semiconductor parts. |
| PTFE (Teflon) and filled PTFE | Virgin, 25% glass, carbon, bronze filled | 2.2 g/cm³, up to 260°C, lowest friction | Good | Seals, gaskets, insulators, chemical parts. Soft and creeps under load. |
| Nylon PA6 / PA66 / cast nylon | Polyamide | 1.14 g/cm³, absorbs 2 to 3% water at room humidity | Good | Wear pads, rollers, gears. Size changes with moisture. |
| UHMW-PE | Ultra high molecular weight polyethylene | 0.93 g/cm³, up to about 80°C | Good | Wear strips, chain guides, food handling parts. Soft, ±0.1 mm is realistic. |
| HDPE / PP | Polyethylene, polypropylene | 0.90 to 0.95 g/cm³ | Good | Chemical tanks, manifolds, cutting boards, lab parts. |
| PC (polycarbonate) | Clear and tinted grades | 1.20 g/cm³, high impact strength | Good | Covers, guards, light pipes, clear fluidic parts. |
| PMMA (acrylic) | Cast and extruded acrylic | 1.19 g/cm³, best optical clarity | Good | Display parts, lenses, light guides, fluidic chips. Cracks with alcohol based cleaners. |
| ABS | General purpose | 1.05 g/cm³ | Good | Prototype housings and fit check parts before tooling. |
| PVDF | Kynar and similar | 1.78 g/cm³, up to about 150°C | Good | Semiconductor chemical delivery, pump and valve parts. |
| PPS | Unfilled and 40% glass filled | 1.35 g/cm³, up to about 220°C | Good | Pump parts, electrical connectors, semiconductor fixtures. |
| PPSU (Radel) | Polyphenylsulfone | 1.29 g/cm³, survives repeated steam sterilization | Good | Medical trays, instrument handles, aircraft interior parts. |
On the machine
- Sharp uncoated or polished carbide, high rake, light cuts and air or water soluble coolant. Heat is the enemy: it melts, smears and stresses the part.
- Thin parts warp when stress is released. Annealed stock and an anneal between roughing and finishing keep PEEK, PEI and POM flat.
- Measure at a stated temperature. PTFE changes volume by about 1% between 19°C and 30°C, so a hot or cold room changes the reading.
- Tolerance to expect
- ±0.05 mm is realistic for most plastics, ±0.025 mm on stable filled grades.
- Finishes that fit
- As machined, vapor or flame polishing for clear plastics, laser marking.
- Read the guide
- 5-Axis Machining PEEK and Engineering Plastics
Composites, laminates and ceramics
Very stiff, light or insulating materials that do not cut like metal. They are abrasive, they fray or crack instead of making a chip, and their dust needs extraction.
| Grade | Equivalents | Typical properties | Machinability | Used for |
|---|---|---|---|---|
| CFRP (carbon fiber) | Laminate and molded parts | 1.5 to 1.6 g/cm³, very stiff | Difficult | 5-axis trimming and drilling of aerospace, motorsport and drone parts. |
| GFRP and G-10 / FR-4 | Glass epoxy laminate (NEMA grade) | 1.8 to 1.9 g/cm³, electrical insulator | Fair | Insulators, PCB fixtures, test sockets, structural spacers. |
| Phenolic laminates | Paper, canvas and linen grades (NEMA XX, CE, LE) | 1.3 to 1.4 g/cm³ | Good | Electrical insulation, low cost gears and wear parts. |
| Machinable glass ceramic (for example Macor) | Fluorophlogopite glass ceramic | 2.52 g/cm³, up to about 800°C continuous | Fair | Vacuum feedthroughs, insulators, prototypes of ceramic parts. |
| Alumina, zirconia, silicon carbide | Fired technical ceramics | 3.9 to 6.0 g/cm³, very hard | Diamond grinding only | Wear parts, semiconductor parts, insulators. Green machined, fired, then ground. |
| Graphite | Isostatic EDM and furnace grades | 1.7 to 1.9 g/cm³ | Good | Sinker EDM electrodes, furnace fixtures, molds for glass and metal. |
On the machine
- Carbon and glass fiber need diamond coated or PCD tools and special geometries to avoid delamination and fraying at the edges.
- Dust is abrasive and a health hazard. Shops cut composites with vacuum extraction and keep it off the machine ways.
- Fully fired alumina and zirconia are ground with diamond, not milled. Machinable glass ceramic and boron nitride cut with carbide.
- Tolerance to expect
- ±0.05 mm on trimmed composites, ±0.01 to ±0.025 mm on machinable ceramics.
- Finishes that fit
- Edge sealing on composites, as machined or lapped on ceramics.
- Read the guide
- 5-Axis Composite Machining: Carbon Fiber Trimming
Machinability compared
Indicative carbide milling speeds. Lower speed means longer cycle time and more tool wear, which is why the same part costs several times more in titanium or Inconel than in aluminum. The shop's own tooling data always decides.
| Material | Cutting speed, carbide milling | Machinability |
|---|---|---|
| Aluminum 6061 / 7075 | 300 to 1,000+ m/min | Excellent |
| Brass C360 | 200 to 450 m/min | Excellent |
| Magnesium AZ31B | 500 to 1,200 m/min | Excellent |
| Free-machining steel 12L14 | 200 to 300 m/min | Excellent |
| Alloy steel 4140, 28 to 32 HRC | 120 to 200 m/min | Good |
| Stainless 304 / 316 | 100 to 180 m/min | Fair |
| Stainless 17-4 PH, H1150 | 80 to 150 m/min | Fair |
| Duplex 2205 | 60 to 120 m/min | Difficult |
| Hardened tool steel, 50 to 60 HRC | 60 to 150 m/min, light engagement | Difficult |
| Titanium Ti-6Al-4V | 40 to 80 m/min | Difficult |
| Inconel 718 | 20 to 50 m/min | Very difficult |
| PEEK, POM | 150 to 500 m/min | Good to excellent |
Why material changes the match
Two shops can both run 5-axis machines and still not be a fit for your material. Titanium and Inconel need rigid setups, low heat and patience. Magnesium needs fire precautions. Plastics need light cuts and careful fixturing so the part does not warp. A shop that runs aluminum all day is not automatically the right shop for any of these. We shortlist on what a shop already cuts, not on the machine it owns.
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Get matched with a 5-axis shopQuestions about material choice
Something else? Email .
My material is not on this page. Can you still help?
Yes. These are the grades we see most often, not a limit on what we take. Name the alloy, the temper and the standard on the RFQ and we match against it directly.
Does material change which shop I get matched with?
Yes. Not every 5-axis shop runs every material well. Titanium and nickel alloys need rigid setups and patience, magnesium needs fire precautions, plastics need light cuts and careful fixturing. We shortlist shops that already run your material, not just any shop with a 5-axis machine.
Do you need the exact grade, or is the material family enough?
The exact grade helps, since 316 and 17-4 stainless behave differently under the tool, as do titanium Grade 2 and Grade 5. If you only know the family, say so and the shop will propose a grade for you to confirm.
Are the EN, JIS and UNS equivalents interchangeable?
Close, not identical. Chemistry limits and mechanical minimums differ slightly between standards. Put the standard you design to on the drawing, and ask the shop before it substitutes an equivalent.
Who supplies the material and the certificate?
Usually the shop buys the material and sends a mill certificate (EN 10204 3.1 or equivalent) with the parts. You can also supply your own stock. Say on the RFQ whether you need certificates, and to which level.
Which material is cheapest to machine?
Brass C360, aluminum 6061 and 2011, free-machining steel and POM cut fastest. Material price matters too: titanium and nickel alloys cost more per kilo and take several times longer to cut. See what drives 5-axis machining cost.