The right material makes your product last, look good and cost less. Tell our finder what your part does and where it is used, compare materials side by side, and avoid the mistakes buyers make most often.
For most CNC parts, start with aluminum 6061 — it is light, low cost and easy to machine. Use stainless steel 304 for parts that touch food or water, 316 for salt water or strong cleaners, and POM for moving plastic parts. Only pay for stronger or rarer materials when your part really needs it.
Updated October 2026 · Written by the Dayao engineering team 署名工程师待定
For most product types, the usual first CNC material is aluminum 6061-T6 for housings and frames, stainless steel 304 for parts that touch food or water, stainless steel 316 for salt water, and POM (Delrin) for moving plastic parts. Tap one of the 8 product types below to see the top material, its finish and two alternatives.
Pick a product to see a quick answer here.
Aluminum 6061-T6 is the right starting point for most CNC machined parts: it weighs 2.70 g/cm³, has a typical tensile strength of about 310 MPa and machines fast. This guide compares 12 metals and 6 plastics. Choose stainless steel when a part touches food, water or chemicals, and a plastic such as POM when it must slide or insulate. Tick Compare on up to 3 cards, or use the Material Finder →
Best forMost parts: housings, brackets, plates and consumer products. Typical 6061-T6: about 310 MPa tensile strength.
Watch outBare 6061 aluminum scratches easily — anodize it. It loses strength above about 150°C.
Best forLight parts that carry high loads — frames, mounts, sports gear. Typical 7075-T6: about 570 MPa, close to some steels.
Watch out7075 costs more than 6061, corrodes more easily and is not a good choice for welding.
Best forFood and drink contact, kitchen and coffee parts, outdoor hardware.
Watch outSlower to machine than aluminum, so parts cost more. 303 machines faster but resists rust a little less.
Best forSalt water, strong cleaning chemicals and medical parts. 316 has 2–3% molybdenum added for better pitting resistance.
Watch out316 costs more than 304 — only pay for it when 304 is not enough.
Best forTurned parts made in volume — screws, shafts, pins and valve parts.
Watch outRusts more easily than 304. Not a good pick for wet or food parts.
Best forStrong stainless parts — shafts, pins, tools and valve parts under high load.
Watch out17-4 PH reaches full strength (about 1,310 MPa in H900 condition) only after heat treatment, which adds time and cost. 热处理能力待核实
Best forBrackets, frames, jigs and sheet metal boxes.
Watch outRusts — it must be painted, powder coated or plated.
Best forSheet metal boxes, covers and panels that need basic rust protection.
Watch outThe zinc layer burns off at welds — touch it up after welding.
Best forSmall precise fittings, knobs, valves and decorative parts.
Watch outStandard C360 contains lead. Use lead-free brass for food or drinking water.
Best forBushings, bearings and wear parts that slide under load.
Watch outHeavier and pricier than brass. Bearing bronze contains lead — use a lead-free grade for food or water.
Best forElectrical and heat parts — bus bars, contacts, heat sinks.
Watch outSoft and sticky to machine; it darkens over time.
Best forPremium parts that must be light, strong and rust-proof.
Watch outTitanium Gr.5 (Ti-6Al-4V) is expensive and slow to machine. 能力待核实
Best forGears, bushings, sliders and parts that move against each other.
Watch outPOM is hard to glue or paint, and is attacked by chlorine and strong acids.
Best forCovers, housings and early prototypes.
Watch outNot for heat, or for outdoor sun without protection.
Best forWear pads, gears and parts that take knocks.
Watch outAbsorbs water, so its size can change.
Best forClear covers, windows and guards.
Watch outScratches easily — handle and pack with care.
Best forHigh heat, chemical and medical parts that replace metal; works continuously up to about 250°C.
Watch outPEEK is very expensive — use it only when nothing cheaper works.
Best forSeals, low-friction liners and chemical contact, up to about 260°C.
Watch outPTFE is very soft (about 20–30 MPa tensile strength), so tight tolerances are hard to hold.
Aluminum 6061-T6 (2.70 g/cm³, about 310 MPa) is the reference most parts start from. Stainless steels are about three times heavier, titanium Grade 5 is about three times stronger than 6061, and machinable plastics range from about 20–30 MPa (PTFE) to about 100 MPa (PEEK). Values are for the grade and condition shown in each row.
| Material | Grade / condition | Density (g/cm³) | Tensile strength | Hardness |
|---|---|---|---|---|
| Aluminum 6061 | 6061-T6 | 2.70 | about 310 MPa | about 95 HB |
| Aluminum 7075 | 7075-T6 | 2.81 | about 570 MPa | about 150 HB |
| Stainless steel 304 | 304, annealed | 8.00 | 515 MPa min. (ASTM A240) | 201 HB max. (ASTM A240) |
| Stainless steel 316 | 316, annealed | 8.00 | 515 MPa min. (ASTM A240) | 217 HB max. (ASTM A240) |
| Stainless steel 416 | 416, annealed | 7.80 | about 515 MPa | about 82 HRB |
| Stainless steel 17-4 PH | 17-4 PH, H900 | 7.80 | about 1,310 MPa | about 40–45 HRC |
| Cold-rolled / mild steel | 1018, cold drawn | 7.85 | about 440 MPa | about 126 HB |
| Galvanized steel | DX51D + Z (EN 10346) | 7.85 | 270–500 MPa | not specified |
| Brass C360 | C360, half hard | 8.50 | about 385 MPa | about 78 HRB |
| Bronze C932 | C932 (SAE 660) | 8.93 | about 240 MPa | about 65 HB |
| Copper | C110, half hard | 8.96 | about 290 MPa | about 83 HRF |
| Titanium Gr.5 | Ti-6Al-4V, annealed | 4.43 | about 950 MPa | about 36 HRC |
| POM (Delrin) | POM copolymer | 1.41 | about 60–70 MPa | about M80 (Rockwell) |
| ABS | ABS, general purpose | 1.05 | about 40 MPa | about R105 (Rockwell) |
| Nylon (PA) | PA6, dry | 1.14 | about 75–85 MPa | about R115 (Rockwell) |
| Polycarbonate (PC) | PC, general purpose | 1.20 | about 60–65 MPa | about M70 (Rockwell) |
| PEEK | PEEK, unfilled | 1.30 | about 100 MPa | about M99 (Rockwell) |
| PTFE (Teflon) | PTFE, virgin | 2.20 | about 20–30 MPa | about 55 Shore D |
Source: Typical values; source: ASM Handbook / MatWeb; minimum and maximum values for 304 and 316 from ASTM A240; galvanized steel range from EN 10346 (DX51D). Actual values depend on temper and supplier certificate.
In most material comparisons, the cheaper and easier-to-machine option is enough: stainless steel 304 instead of 316 for indoor and kitchen parts, aluminum 6061 instead of 7075 unless the part carries a heavy load, and anodizing instead of powder coating for aluminum parts with tight fits. Each of the 14 pairs below gives a short answer, when to choose each one, and a product example.
Stainless steel 304 is enough for most kitchen, coffee and indoor parts and costs less. Stainless steel 316 adds 2–3% molybdenum, so choose 316 for salt water, chlorine or strong chemicals. Both grades have the same 515 MPa minimum tensile strength (ASTM A240) and both are common for food contact.
Source: Ratings are relative (1–5) for quick comparison. Weight and strength are typical values; source: ASM Handbook / MatWeb; actual values depend on temper and supplier certificate.
In a productHand grinder shaft and catch cup: 304. Boat fitting or parts washed with chlorine: 316.
“18/8” stainless steel means about 18% chromium and 8% nickel. Stainless steel 304 is the most common 18/8 grade, so in daily use they are the same thing. Use “18/8” on cups and cutlery labels; write “304” on a drawing or purchase order so the supplier must deliver one exact grade.
| Fact | “18/8” | “304” |
|---|---|---|
| What it is | “18/8” is a label: about 18% chromium, 8% nickel | 304 is one exact grade (AISI 304 / SUS304 / UNS S30400) |
| Can mean | “18/8” can mean 304, and sometimes 302 or 303 | “304” means 304 only |
| Use it on | “18/8” belongs on product labels and listings | “304” belongs on drawings, orders and material certificates |
Source: ASTM A240 composition for UNS S30400: 17.5–19.5% chromium, 8.0–10.5% nickel.
In a productYour product label can say 18/8. Your drawing should say SUS304 / AISI 304.
For machined parts, five stainless steel grades cover almost everything: 303 and 416 cut fastest, 304 is the everyday food-safe grade, 316 handles salt and chemicals, and 17-4 PH is the strongest (about 1,310 MPa after H900 heat treatment). Start with 304 and change grade only for a clear reason.
| Grade | Rust resistance | Machining | Strength | Food contact |
|---|---|---|---|---|
| 303 | Good | Very easy | Medium | Sometimes |
| 304 | Very good | Medium | Medium (515 MPa min.) | Yes — very common |
| 316 | Best | Medium | Medium (515 MPa min.) | Yes — common |
| 416 | Fair | Very easy | High (can be hardened) | Usually no |
| 17-4 PH | Very good | Medium | Very high (about 1,310 MPa, H900) | Some machinery parts |
Source: ASTM A240 (stainless steel plate, sheet and strip) for 304/316 minimum strength; typical values for 17-4 PH from ASM Handbook / MatWeb.
In a productCoffee grinder: 304 for parts that touch coffee; 416 or 17-4 PH only for inner, dry parts that need strength.
Aluminum 7075-T6 is much stronger than 6061-T6 (about 570 vs 310 MPa typical tensile strength). Aluminum 6061 costs less, resists corrosion better, welds well and anodizes to an even color. Choose 6061 unless the part is a light part that carries a heavy load.
Source: Ratings are relative (1–5) for quick comparison. Weight and strength are typical values; source: ASM Handbook / MatWeb; actual values depend on temper and supplier certificate.
In a productGrinder body and handle arm: 6061. Bike or drone frame part: 7075.
Aluminum 6061-T6 is stronger (about 310 MPa) and is the better choice for CNC machined parts. Aluminum 6063-T6 is softer (about 240 MPa) and gives a smoother anodized surface; it is mainly extruded (pushed through a die) into window frames, rails and heat sinks.
| Fact | 6061 | 6063 |
|---|---|---|
| Tensile strength (T6, typical) | 6061-T6: about 310 MPa | 6063-T6: about 240 MPa |
| Hardness (T6, typical) | 6061-T6: about 95 HB | 6063-T6: about 73 HB |
| Usually made by | 6061: CNC machining from plate or bar | 6063: extrusion (pushed through a die) |
| Anodized surface | 6061: good | 6063: very smooth |
| Typical parts | 6061: bodies, housings, brackets | 6063: window frames, rails, heat sinks |
Source: Ratings are relative (1–5) for quick comparison. Weight and strength are typical values; source: ASM Handbook / MatWeb; actual values depend on temper and supplier certificate.
In a productA machined grinder body: 6061. A long extruded handle rail cut to length: 6063.
Aluminum 6061 weighs about one third as much as stainless steel 304 (2.70 vs 8.0 g/cm³) and is usually cheaper to machine. Stainless steel is harder, stronger and stays rust-free without a coating. Aluminum does not rust like steel, but it can corrode in salt water — anodizing protects it.
Source: Ratings are relative (1–5) for quick comparison. Weight and strength are typical values; source: ASM Handbook / MatWeb; actual values depend on temper and supplier certificate.
In a productHand grinder: anodized aluminum body, stainless steel burrs and shaft.
Titanium Grade 5 is about 45% lighter than stainless steel 304 (4.43 vs 8.0 g/cm³), stronger (about 950 MPa) and even more corrosion resistant. But titanium costs several times more and machines slowly. Stainless steel is the value choice for most food, kitchen and industrial parts.
Source: Ratings are relative (1–5) for quick comparison. Weight and strength are typical values; source: ASM Handbook / MatWeb; actual values depend on temper and supplier certificate.
In a productPremium travel grinder handle: titanium. Standard model: stainless steel or aluminum.
Aluminum 6061 is lighter than titanium Grade 5 (2.70 vs 4.43 g/cm³) and far cheaper to machine. Titanium Grade 5 is roughly three times stronger (about 950 vs 310 MPa) and does not corrode in salt water. Choose titanium only when a part needs high strength and low weight together.
Source: Ratings are relative (1–5) for quick comparison. Weight and strength are typical values; source: ASM Handbook / MatWeb; actual values depend on temper and supplier certificate.
In a productPhone case or grinder body: aluminum. Small high-stress pin or premium accessory: titanium.
Brass is copper plus zinc: brass C360 is one of the easiest metals to machine, with a bright gold color, ideal for fittings and decorative parts. Bronze is copper plus tin: bronze C932 is tougher against wear, ideal for bushings and bearings. Both standard grades contain lead — use lead-free grades for food or drinking water.
Source: Ratings are relative (1–5) for quick comparison. Weight and strength are typical values; source: ASM Handbook / MatWeb; actual values depend on temper and supplier certificate.
In a productDecorative grinder knob: brass. Bushing that the shaft spins in: bronze.
Delrin (POM) is stiffer, more slippery and keeps its size, so it is the better plastic for precise gears, bushings and sliders. Nylon (PA) is tougher against knocks but absorbs water and swells. For moving parts with tight fits, choose Delrin; for impact and wear pads, nylon.
Source: Ratings are relative (1–5) for quick comparison. Weight and strength are typical values; source: ASM Handbook / MatWeb; actual values depend on temper and supplier certificate.
In a productGrinder handle knob or adjustment gear: POM. Machine guide roller: nylon.
PTFE (Teflon) is the most slippery and chemical-proof plastic and works up to about 260°C, but it is very soft (about 20–30 MPa). PEEK is strong (about 100 MPa), stiff, works up to about 250°C and costs much more. Use PTFE for seals and liners, PEEK for strong high-heat parts.
Source: Ratings are relative (1–5) for quick comparison. Weight and strength are typical values; source: ASM Handbook / MatWeb; actual values depend on temper and supplier certificate.
In a productSeal in a coffee machine: PTFE. Insulating part next to a heater: PEEK.
Anodizing turns the aluminum surface itself into a hard oxide layer of about 1.8–25 µm (MIL-A-8625 Type II): it does not peel and keeps sharp details and laser-engraved logos. Powder coating is a thicker paint layer of about 50–100 µm: more colors, works on steel too, but can chip at edges.
| Fact | Anodizing | Powder coating |
|---|---|---|
| Thickness | Anodizing (Type II): 1.8–25 µm per MIL-A-8625 | Powder coating: typically about 50–100 µm |
| Works on | Anodizing: aluminum (and titanium) | Powder coating: steel, aluminum and most metals |
| Peeling or chipping | Anodizing does not peel — it is part of the metal | Powder coating can chip at sharp edges |
| Colors | Anodizing: many colors, with a metal look | Powder coating: almost any color and texture |
Source: MIL-A-8625F, Anodic coatings for aluminum and aluminum alloys (US Department of Defense); powder thickness is a typical industry range.
In a productGrinder body: anodized. Steel machine frame: powder coated.
Type II anodizing (MIL-A-8625) is 1.8–25 µm thick, smooth and available in many colors — the usual choice for consumer products. Type III hard anodizing is 12.7–115 µm thick (50.8 µm if the drawing does not say) and much harder, made for wear, but colors are limited mostly to dark gray and black.
| Fact | Type II | Type III |
|---|---|---|
| Thickness (MIL-A-8625) | Type II: 1.8–25 µm (0.00007–0.001 in) | Type III: 12.7–115 µm (0.0005–0.0045 in); 50.8 µm if not specified |
| Hardness | Type II: good for daily handling | Type III: very hard — made for wear |
| Colors | Type II: many colors | Type III: mostly dark gray or black |
| Size change | Type II: very small | Type III: about half the layer grows outward — plan for it on tight fits |
Source: MIL-A-8625F, Anodic coatings for aluminum and aluminum alloys (US Department of Defense).
In a productColored grinder body: Type II. Aluminum slide rail or piston: Type III.
Passivation and electropolishing both help stainless steel resist rust. Passivation is a chemical clean that removes free iron; the part looks the same and its size does not change. Electropolishing removes a very thin layer of metal, so the stainless part becomes smoother, brighter and easier to clean — and costs more.
| Fact | Passivation | Electropolishing |
|---|---|---|
| What it does | Passivation cleans free iron off the stainless surface | Electropolishing removes a very thin layer of metal |
| Look | Passivation: no change | Electropolishing: smoother and brighter |
| Size change | Passivation: none | Electropolishing: small — plan for it on tight fits |
| Cost | Passivation: lower | Electropolishing: higher |
Source: General finishing practice for stainless steel; ask for the process standard your industry uses.
In a productGrinder shaft: passivated. Food machine part with a hygiene requirement: electropolished.
Most quality problems with CNC machined parts come from the material or finish choice, not from the machine. The most common are rust spots on stainless steel, anodized color changing between batches, coating that chips at sharp edges, and threads that no longer fit after coating. Each fix below is something you can write on the drawing or purchase order before production starts.
Why: Iron dust from cutting tools or nearby carbon steel sticks to the stainless surface and rusts, or the thin chromium-oxide layer was damaged during machining.
Have stainless steel parts passivated (a chemical clean that removes free iron) or electropolished after machining, keep them away from carbon-steel dust, and never clean them with steel wool. 钝化是否提供待核实
Why: Anodizing color depends on the aluminum alloy (6061 and 7075 take dye differently), the material lot and the dye bath settings.
Approve a color sample, keep every matching part in the same alloy (for example all 6061-T6), and anodize matching parts in one batch.
Why: A sharp machined edge on aluminum or steel holds only a thin layer of coating, so coatings wear or chip at the edge first.
Ask for all sharp edges to be broken with a small chamfer or radius on the drawing, especially on parts that will be powder coated or anodized.
Why: Powder coating (typically about 50–100 µm thick) and plating add material inside tapped holes and on threads and fits.
Mask threads and fitting surfaces before coating, or state on the drawing whether dimensions apply before or after coating.
Why: Aluminum and stainless steel touching in wet or salty places form a galvanic cell, and the aluminum corrodes first (galvanic corrosion).
Separate aluminum and stainless steel with insulating washers or coated screws, anodize the aluminum, and keep the joint dry.
Why: Nylon (PA) absorbs water from the air and swells, and most plastics grow much more with heat than aluminum or steel.
Use POM (Delrin) for tight-fitting plastic parts, measure plastic parts at room temperature, or allow a looser tolerance on nylon parts.
Why: A slow-to-machine or costly material such as stainless 316, titanium or PEEK was chosen where aluminum 6061 or stainless 304 would work.
Start with aluminum 6061 or stainless steel 304, and upgrade only the parts that really need more strength, heat or rust resistance.
Why: Some suppliers swap in a cheaper grade, for example stainless 201 instead of 304: it looks the same but rusts faster.
Ask for a material certificate (mill certificate) with every batch of metal, and check critical stainless parts with a handheld XRF analyzer. 来料材质证明核查流程待核实
Why: Smooth, shiny polished or brushed surfaces on stainless steel and aluminum show skin oils very clearly.
Choose bead blasting plus anodizing on aluminum, or bead blasting on stainless steel, for a soft matte look that hides fingerprints.
Stainless steel 304 and 316 are the standard choice for machined parts that touch food or drink; anodized aluminum 6061 and food-grade POM, PTFE or PEEK are also used. A part is food safe only when three conditions are met: the material grade suits food contact, the finish suits food contact, and the finished part passes the buyer’s own compliance tests for US FDA 21 CFR or EU 1935/2004 and EU 10/2011 rules.
| # | Part | Typical material | Why | Finish |
|---|---|---|---|---|
| 1 | Body | Aluminum 6061 | Light, easy to machine, takes color well | Anodizing |
| 2 | Burrs | Hardened stainless steel | Stays sharp and does not rust; ceramic or titanium-coated are other options | — |
| 3 | Drive shaft | Stainless steel | Strong, straight and rust-free where it meets coffee | Polishing |
| 4 | Adjustment ring | Aluminum or stainless steel | Must hold precise steps for each grind setting | Anodizing or brushing |
| 5 | Bearing seat / pressure ring | Stainless steel | Keeps the shaft centered under load | — |
| 6 | Handle knob | Wood, POM or aluminum | Comfortable to hold; POM is light and smooth | Varies |
| 7 | Catch cup | Aluminum or stainless steel | Touches the ground coffee — choose food-contact grades | Anodizing or polishing |
Hand coffee grinder materials shown are typical industry choices. The exact materials in our own grinder line: 待核实 · See the product OEM/ODM page.
Source: US FDA 21 CFR Part 177 (food-contact polymers, e.g. §177.2470 POM copolymer, §177.1550 PTFE, §177.2415 PEEK); Regulation (EC) No 1935/2004 (all food-contact materials in the EU); Regulation (EU) No 10/2011 (food-contact plastics, overall migration limit 10 mg/dm²); US Safe Drinking Water Act §1417 (lead-free = 0.25% weighted-average lead).
The right surface finish depends first on the material: anodizing works only on aluminum (and titanium), powder coating and plating protect steel, and passivation or electropolishing helps stainless steel resist rust. Under MIL-A-8625, Type II anodizing is 1.8–25 µm thick and Type III hard anodizing 12.7–115 µm (50.8 µm if the drawing gives no thickness), so plan for coating thickness on threads and fits. Anodizing vs powder coating →
Sand or bead blasting gives an even matte surface that hides tool marks.
Powder coating adds a thick colored layer, typically about 50–100 µm, that protects steel against rust.
Polishing gives a shiny, smooth, mirror-like surface on stainless steel, brass and aluminum.
Electroplating adds a thin metal layer (nickel, chrome or zinc) for shine and rust protection.
Anodizing (MIL-A-8625 Type II) grows a hard, colored oxide layer of 1.8–25 µm from the aluminum itself.
Brushing gives fine straight lines for a satin look on stainless steel, aluminum and brass.
Silk-screen printing puts logos, labels and scales on the part in ink.
Laser engraving marks a permanent logo, serial number or scale on metal parts.
Hard anodizing (MIL-A-8625 Type III) builds a 12.7–115 µm, very hard layer for aluminum parts that rub or wear.
Passivation is a chemical clean that removes free iron and helps stainless steel resist rust.
Electropolishing gives stainless steel a very smooth, bright surface that is easy to clean.
Black oxide gives steel a thin black layer for a dark look and light rust protection.
| Finish ↓ / material → | Aluminum | Stainless | Steel | Brass / copper | Plastics |
|---|---|---|---|---|---|
| Sand blasting | Recommended | Recommended | Recommended | Possible | — |
| Spray / powder coating | Recommended | Possible | Recommended | — | Possible |
| Polishing | Possible | Recommended | Possible | Recommended | Possible |
| Electroplating | Possible | Possible | Recommended | Recommended | — |
| Anodizing | Recommended | — | — | — | — |
| Brushing | Recommended | Recommended | Possible | Recommended | — |
| Silk-screen | Recommended | Recommended | Recommended | Recommended | Recommended |
| Laser engraving | Recommended | Recommended | Recommended | Recommended | Possible |
| Hard anodizing (Type III) | Recommended | — | — | — | — |
| Passivation | — | Recommended | — | — | — |
| Electropolishing | — | Recommended | — | — | — |
| Black oxide | — | Possible | Recommended | — | — |
Good choicePossible— Not usedSurface finishing services →
Source: MIL-A-8625F, Anodic coatings for aluminum and aluminum alloys (US Department of Defense) for Type II and Type III thickness; powder coating thickness and finish/material pairings are typical industry practice.
Material choice changes the price of a CNC part in two ways: the raw material price and how fast the material machines. Aluminum 6061 is usually the cheapest metal to machine because it cuts fast and wears tools slowly. Stainless steel 316, titanium Grade 5 and PEEK cost the most. The effect is largest on parts where a lot of material is cut away.
Depends on part size, shape and quantity. Your quote gives the real price.
The questions buyers ask most about CNC machining materials have short answers: aluminum 6061 is the usual first choice and the cheapest metal to machine, stainless steel 304 suits most food and wet parts, 316 is needed for salt water or chlorine, and POM (Delrin) is the best plastic for moving parts. The 16 answers below give the conditions and exceptions.
Reviewed by the Dayao engineering team · Updated October 2026
If you are not sure which material to use, send Dayao your drawing with three facts: how the part is used, what it touches (food, water, salt or chemicals) and how many you need. An engineer reviews every drawing and suggests a material and finish in the quote. An NDA can be signed before you share files.
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