Materials for CNC Machined Parts, With Grade Equivalents
The grades shops in Vietnam are asked to machine most often, with their UNS, EN and JIS names side by side, so a drawing written to one standard can be quoted from stock held to another.
Strength values are typical for the stated condition and vary with size, temper and standard. Equivalents are nearest grades, not identical chemistry. For what is held as local stock and what is ordered in, see what is actually stocked.
Aluminium
The default for machined parts: light, fast to cut and easy to anodise. 6061-T6 is what most shops cut every day.
| Grade | UNS | EN | JIS | Typical tensile strength | Use it for |
|---|---|---|---|---|---|
| 6061-T6 | A96061 | EN AW-6061 | A6061 | about 310 MPa | General machined parts, brackets, housings, fixtures |
| 6063-T5/T6 | A96063 | EN AW-6063 | A6063 | about 185 to 240 MPa | Extrusion based profiles, heat sinks, decorative anodising |
| 7075-T6/T651 | A97075 | EN AW-7075 | A7075 | about 570 MPa | Highly loaded parts, aerospace style structures, tooling plates |
| 2024-T351 | A92024 | EN AW-2024 | A2024 | about 470 MPa | Fatigue loaded parts. Poor corrosion resistance unless coated |
| 5052-H32 | A95052 | EN AW-5052 | A5052 | about 230 MPa | Sheet and plate parts near salt water. Gummier to machine |
Stainless steel
Chosen for corrosion, hygiene or appearance. Pick the grade by what touches the part, then check that it machines well enough for the quantity.
| Grade | UNS | EN | JIS | Typical tensile strength | Use it for |
|---|---|---|---|---|---|
| 303 | S30300 | 1.4305 | SUS303 | about 620 MPa | Turned parts with no corrosive exposure. The fastest stainless to cut |
| 304 | S30400 | 1.4301 | SUS304 | about 515 to 620 MPa | General purpose. Food equipment, enclosures, fittings |
| 316L | S31603 | 1.4404 | SUS316L | about 485 to 580 MPa | Marine, chemical and food contact where chlorides are present |
| 17-4PH | S17400 | 1.4542 | SUS630 | about 1000 to 1310 MPa aged | High strength stainless shafts and valve parts. Specify the ageing condition |
| 420 | S42000 | 1.4021 | SUS420J1 | hardenable to about 50 HRC | Cutting edges, wear parts, moulds. Moderate corrosion resistance |
Carbon, alloy and tool steel
The cheapest metal by weight and the strongest per unit cost. Usually plated, painted or oiled, and often heat treated.
| Grade | UNS | EN | JIS | Typical tensile strength | Use it for |
|---|---|---|---|---|---|
| 1018 / low carbon | G10180 | C15E (1.1141), closest | S15C, closest | about 440 MPa cold drawn | Weldable general parts, case hardened pins |
| 1045 | G10450 | C45 (1.0503) | S45C | about 570 to 700 MPa | Shafts, gears and pins, often induction hardened |
| 4140 | G41400 | 42CrMo4 (1.7225) | SCM440 | about 655 MPa annealed, higher when hardened | Highly loaded shafts, tooling, hydraulic parts |
| H13 | T20813 | X40CrMoV5-1 (1.2344) | SKD61 | used at about 44 to 52 HRC | Hot work dies, die casting inserts |
| D2 | T30402 | X153CrMoV12 (1.2379) | SKD11 | used at about 58 to 62 HRC | Cold work punches, dies and wear plates |
Brass, copper and titanium
Brass is the easiest metal to machine. Copper is chosen for conductivity. Titanium is chosen for strength per weight and corrosion, and is the hardest of the three to cut.
| Grade | UNS | EN | JIS | Typical tensile strength | Use it for |
|---|---|---|---|---|---|
| C360 free cutting brass | C36000 | CW614N | C3604 | about 340 to 470 MPa | Fittings, connectors, threaded inserts, valve parts |
| C110 copper (ETP) | C11000 | Cu-ETP (CW004A) | C1100 | about 220 to 300 MPa | Bus bars, electrodes, heat spreaders |
| Titanium grade 2 | R50400 | 3.7035 | Class 2 (JIS H 4650) | about 345 MPa minimum | Corrosion resistant parts with moderate load |
| Titanium grade 5 (Ti-6Al-4V) | R56400 | 3.7165 | Class 60 (JIS H 4650) | about 895 MPa minimum | Structural parts where weight and strength both matter |
Engineering plastics
Plastics are quoted like metals but behave differently on the machine: they move with heat and moisture, and clamping pressure can deform them. Name the grade, not the family, because "nylon" covers materials with very different properties.
| Plastic | Common names | Typical tensile strength | Machining note | Use it for |
|---|---|---|---|---|
| POM (acetal) | Delrin (homopolymer), POM-C (copolymer) | about 60 to 70 MPa | Machines cleanly and holds size well | Gears, bushings, wear strips, food contact parts in suitable grades |
| PA6 and PA66 (nylon) | Nylon 6, nylon 66, cast nylon | about 70 to 85 MPa dry | Absorbs moisture and grows, so tight tolerances drift | Rollers, wear pads, insulators |
| PTFE | Teflon | about 20 to 35 MPa | Soft and creeps under clamping. Tolerances are wide | Seals, low friction slides, chemical contact |
| PEEK | Unfilled, glass or carbon filled | about 90 to 100 MPa unfilled | Machines well. The stock is expensive and often imported | High temperature, chemical and semiconductor equipment parts |
| UHMW-PE | UHMW, PE 1000 | about 20 to 40 MPa | Very soft, poor dimensional stability | Wear liners, guides, chain tracks |
Plan tolerances on plastic parts about one class wider than on the same part in aluminium unless the material is POM or PEEK. More on grades and moisture in the engineering plastics guide.
Machinability decides the cycle time
Two parts with the same geometry can differ by a factor of three in machine time because of the material alone. Free cutting brass and 6061 aluminium are cut at high speed with long tool life. 304 and 316 stainless work harden, so feeds and speeds drop and tools wear faster. Titanium conducts heat poorly, which keeps the heat in the cutting edge and forces slower cutting. Hardened steel above about 45 HRC is usually ground or cut by EDM rather than milled.
That is why changing 316L to 303 on a dry indoor part, or 7075 to 6061 on a lightly loaded bracket, often moves the price more than any tolerance change. The quote breakdown shows where material and machine time sit in a price.
Standards behind the designations
UNS numbers come from the unified numbering system used with ASTM and SAE specifications. EN designations come from European standards such as EN 573 for wrought aluminium and EN 10088 for stainless steel. JIS designations come from Japanese Industrial Standards such as JIS G 4303 for stainless bar and JIS H 4000 for aluminium sheet and plate.
Shops in Vietnam buy bar stock certified to several of these systems, often JIS or Chinese GB standards. A drawing that names the grade in the standard you need, with the equivalent you accept, removes a round of questions. The unified numbering system is a good starting point for cross references.
Choosing a material by what the part must do
Start from the requirement, not from the grade the last drawing used. These pairings cover most machined parts.
- Lightest part that is still stiff6061-T6 aluminium first, 7075-T6 if the stress calculation says 6061 is not enough. Titanium only when weight and strength both matter and the budget allows.
- Salt water, chlorides or food316L stainless, or titanium grade 2 where 316L is not enough. 304 is fine for dry indoor use and costs less.
- Wear and hardness4140 hardened, 420 stainless, or D2 for cutting and forming edges. Hardness is reached by heat treatment, which is usually a separate supplier.
- High volume turned partsFree machining grades: 303 stainless, C360 brass, 12L14 steel. They cut fast, and cycle time is most of the price at volume.
- Electrical or thermal conductionC110 copper for conductivity, 6061 or 6063 aluminium when cost and weight matter more than the last percent of conduction.
- Electrical insulation or low frictionPOM for precision, PEEK for heat and chemicals, PTFE for friction and chemistry when tolerance is wide.
Grade comparisons in more depth: 6061 vs 7075, 303 vs 304 vs 316 and 1045, 4140 and 4340 steel.
Writing the material line
A material callout that gets a fast, accurate quote has three parts: the grade, the temper or condition and whether a substitute is acceptable. "6061-T6 or equivalent" can be quoted from stock. "Aluminium" cannot be quoted at all without a question.
Add hardness where it matters, and state whether it applies before or after machining. If documents must travel with the parts, ask for a mill certificate in the RFQ, not after the order. Coatings that follow the material, such as anodise on aluminium or passivation on stainless, are listed with their thickness on the standards page.
How material shapes the match
Material is the second filter after process when we pick shops for an RFQ. A 6061 part can go to almost any shop. A titanium, PEEK or tool steel part goes to shops that have cut that material before and can say on which machine. The process side is on the processes page, and the sector side on the industries page.
Questions about materials
Are the EN and JIS grades in these tables exact equivalents?
No. They are the nearest grades in common use, with similar chemistry and properties, but limits differ between standards. If the grade is functional, name the standard you require and ask for a mill certificate against it. If a near grade is acceptable, write "or equivalent" on the drawing.
Which material is cheapest to machine?
Per part, usually 6061 aluminium or C360 brass, because they cut fast and are widely stocked. Mild steel is cheaper per kilogram but cuts slower. Stainless, titanium and hardened steel cost more in both material and machine time.
Can I get a mill certificate with the parts?
Yes, ask for it in the RFQ. A mill certificate traces the bar to a heat of material with chemistry and mechanical properties. It has to be requested before the shop buys the stock, because a certificate cannot be produced for bar that was bought without one.
Does the material change the lead time?
Often more than the machining does. Common aluminium, stainless and brass are usually held as bar stock. Tool steel, PEEK, titanium and nickel alloys are more often ordered in, which adds days or weeks before cutting starts.
Material and grade decided?
Send the drawing and we match it with up to 3 shops in Vietnam that hold or can source that grade. You hear from us within 24 business hours.