Aluminium grade selection — 6061 vs 7075 vs 2024 and the cost gap
Aluminium is the most-machined metal at a CNC shop, and the grade is the first cost decision. 6061-T6 is the general-purpose grade — good machinability, good corrosion resistance, weldable, anodisable, and the cheapest of the structural aluminuim grades. 7075-T6 is the high-strength grade — stronger than 6061, harder, and the choice for aerospace and high-stress parts, but it is more expensive, harder to anodise, and not weldable. 2024-T3 is the classic aerospace grade — high strength-to-weight, but poor corrosion resistance and not weldable, so it needs coating or painting.
The machinability difference is real. 6061-T6 cuts cleanly with carbide at high surface speed, the chip breaks well, and the tool life is long. 7075-T6 is harder and the tool pressure is higher, so the surface speed drops and the tool life is shorter; the surface finish is excellent, though, because the harder material shears rather than tears. 2024-T3 is between the two on machinability but the copper content makes it corrosive in service, so it is almost always coated or painted. Your move is to specify the grade by the service requirement — 6061 for general structural, 7075 for high stress, 2024 for classic aerospace — and to accept the cost that comes with the higher grade.
The cost gap is roughly 1.5x from 6061 to 7075 and roughly 1.8x from 6061 to 2024, at the billet level. The machining cost rises with the grade too, because the harder grades need slower speeds and shorter tool life. A part quoted in 7075 that could be 6061 is paying for strength the part does not use; a part quoted in 6061 that needs 7075 will fail in service. The engineer's decision is the grade; your decision is to confirm the grade at the quote stage and not let the shop substitute without written approval.
The tolerance case for aluminuim is favourable — the material is stable, cuts cleanly, and holds the ±0.003 mm milling and ±0.002 mm turning bands that the facility behind this guide runs on 100+ machines with Hexagon CMM verification. Ppk ≥ 1.67 initial on key characteristics and Cpk ≥ 1.33 in production apply on the routed process, under ISO 9001:2015 (116024/A/0001/UK/En) and IATF 16949:2016 (131941/A/0001/SM/En, design clause 8.3 excluded). Specify the grade — not just "aluminium" — and ask for the material certificate with the heat number at delivery. Contact Felipe Iglesias at [email protected] or +86 13126536955 to confirm the grade and the cost at the quote stage.
The shop behind this aluminium guide — grade confirmed at quote and at delivery
Backing this guide is a 6,800 m² plant at No. 8, Shuibian Songyuan Road, Hengli Town, Dongguan, Guangdong, China 523470, running 100+ CNC machines — Mazak VARIAXIS I-600 and INTEGREX I-250H S, TSUGAMI B0206-III/B0205-III, STAR SR-32JII / SR-32J Type N, Citizen Cincom A20-3F7 — plus 3-, 4- and 5-axis milling and turning, 5+ wire EDM and a Hexagon CMM bench with 20+ gauges.
Milling holds ±0.003 mm, turning ±0.002 mm, and grinding or wire EDM ±0.002 mm, all checked on a Hexagon CMM with the 10:1 gauge rule applied to every feature. Capability: Ppk ≥ 1.67 initial and Cpk ≥ 1.33 in production on key characteristics. Certified to ISO 9001:2015 (116024/A/0001/UK/En), IATF 16949:2016 (131941/A/0001/SM/En, design clause 8.3 excluded, openly disclosed) and ISO 14001:2015 (116024/B/0001/UK/En), held by Dongguan Zhuohang Ltd, USCC 91441900MA4UWT6X39, established 2005. Customers across Austria, Belgium, the Czech Republic, Denmark, France, Germany, Greece, Hungary, Ireland, Italy, the Netherlands, Spain, Sweden and the United Kingdom in Europe; Brazil, Canada, Mexico and the United States in the Americas; China, Israel, Japan, Singapore and Sri Lanka in Asia; Australia and New Zealand in Oceania; and South Africa in Africa are supplied from China, worldwide. Contact Felipe Iglesias at [email protected] or +86 13126536955 to begin the quote, and ask for the certificate numbers, the machine list and a past CMM report together.
- more than 100 machines including 20+ 5-axis centres; 100+ staff, 80%+ skilled technicians.
- Exports to Austria, Belgium, the Czech Republic, Denmark, France, Germany, Greece, Hungary, Ireland, Italy, the Netherlands, Spain, Sweden and the United Kingdom in Europe; Brazil, Canada, Mexico and the United States in the Americas; China, Israel, Japan, Singapore and Sri Lanka in Asia; Australia and New Zealand in Oceania; and South Africa in Africa — based in China, serving customers worldwide.
- Aluminum: Aluminium is the forgiving end of the spectrum: it cuts fast, conducts heat away from the edge, and is easy on tools.
- Grades in regular use: 6061-T6 for general work and anodising, 7075-T6 for strength, 6082 for structural use in Europe, 2024 where fatigue matters.
- Incoming stock is verified against the mill certificate before it is cut.
The cutting mechanism of aluminum
Aluminium is the forgiving end of the spectrum: it cuts fast, conducts heat away from the edge, and is easy on tools. The problems are different, built-up edge at low speed, chip evacuation in deep pockets, and the fact that a fast cycle time makes the setup time a larger fraction of the cost, so batch size dominates price.
Cast plate and wrought bar behave differently under stress relief and can move differently after machining, worth stating on the drawing.
Which certifications apply, and what do they exclude?
Three certificates, each with a number you can check with the registrar:
| Standard | Certificate number | Scope note |
|---|---|---|
| ISO 9001:2015 | 116024/A/0001/UK/En | Quality management system |
| IATF 16949:2016 | 131941/A/0001/SM/En | Automotive QMS, excludes clause 8.3 product design |
| ISO 14001:2015 | 116024/B/0001/UK/En | Environmental management system |
The IATF 16949 certificate excludes clause 8.3 (product design). That is normal for a build-to-print manufacturer and it is stated here rather than left for an auditor to discover: we cut to the drawings you provide, it does not originate the design.
Grade selection for aluminum
6061-t6, 7075-t6, 6082, 2024, and cast plate grades are the grades that come up in practice. 6061-T6 for general work and anodising, 7075-T6 for strength, 6082 for structural use in Europe, 2024 where fatigue matters.
Your grade selection is usually settled by the service environment — corrosion, strength, or temperature, and only then by machinability. If you choose on machinability first, your part meets the drawing and fails in service.
Dimensional behaviour of aluminum
High thermal expansion means a part measured warm will measure differently when cool. On a tight-tolerance part the finishing pass is taken after the part has returned to ambient, and the measurement is taken at 20 °C.
The general rule for your part is that a tolerance is held by the process, not by the machine. Where a feature is tight, the finishing pass is separated from roughing, the part is allowed to stabilise, and the measurement is taken at a controlled temperature.
Finishing options for aluminum
Anodising (Type II and Type III hardcoat), chem film, and powder coat are all routine. Type II adds roughly 5–15 µm per surface, which must be allowed for on threaded and press-fit features.
You specify finishing on the drawing, not assume it at the end. Where a coating adds thickness, threaded and press-fit features need the allowance stated, because a coating applied after inspection changes the fit.
Why aluminum costs what it costs to cut
The problems are different — built-up edge at low speed, chip evacuation in deep pockets, and the fact that a fast cycle time makes the setup time a larger fraction of the cost, so batch size dominates price.
The lever that matters most for you is usually design rather than process: pocket depth, corner radius, and wall thickness change cycle time more than any tooling choice, because they determine the tool that can be used and therefore how much material can be removed per minute.
What design decisions move the cost on China CNC machining?
Aluminium cuts fast, so setup time becomes a larger share of the cost and batch size dominates the unit price. The design levers are chip evacuation in deep pockets and wall stability — a 1 mm wall on a large pocket will move under cutting pressure even in aluminium, and holding it flat costs a slower finishing pass.
This is cheaper to settle at quote time than once parts already exist, because the changes are usually trivial on the drawing and significant on the machine.
What capacity sits behind this?
Total machine count is not the question. The question is how many machines sit in the family that makes your part, because that is the queue your part waits in. The floor runs over a hundred machines: 50+ three-axis centres for prismatic work, 20+ four-axis, 20+ five-axis, 25+ turning and mill-turn centres, Swiss-type lathes for long slender parts, precision grinding and wire EDM for the tightest features.
The spare capacity in that family is what lets a part move to another lane rather than sit in a queue when a machine is pulled for service. That, not the headline machine, is what protects a delivery date.
What tolerance applies?
±0.003 mm on CNC milling, ±0.002 mm on CNC turning; ±0.002 mm where precision grinding or wire EDM is used, set feature by feature when we quote.
Which entity is responsible for the work?
Dongguan Zhuohang Ltd, Registration No. 91441900MA4UWT6X39, in operation since 2005.
What this shop actually runs
Capability evidence should come as specifics, not slogans. Behind this guide is a 6,800 m2 plant in Dongguan, China running 100+ CNC machines with 100+ staff. The machine list by category:
- 5-axis machining centres (10+) - Mazak VARIAXIS I-600 (510/910/510 mm travel, 12,000 rpm, 22 kW, 71.6 N·m, 30-tool BT40) and Mazak INTEGREX I-250H S (B-axis 0.0001°, 24 kW, 124 N·m, 38-tool HSK-A63). Made for compound-angle parts, single-setup multi-face prismatic work, and aerospace fittings where datum transfer loss is unacceptable.
- 3-axis / 4-axis machining centres (50+) - Brother SPEEDIO S500Z2N / S700Z2N (10,000 rpm, 14/21-tool ATC, 0.7 s tool-to-tool, Z-axis 2.2 G) and Mazak VCE-430A L / VCE-570C L (10,000 rpm, 118 N·m, 24-tool ATC). Made for prismatic parts, plates, brackets, housings.
- Swiss-type turning centres (10+) - Citizen Cincom A20-3F7 (Φ20 mm, 10,000 rpm), TSUGAMI B0206-III / B0205-III (Φ20 mm, 0.1 µm), STAR SR-32JII / SR-32J Type N (Φ32 mm, 8,000 rpm). Made for long, slender rotational parts at ±0.002 mm.
- CNC turning centres (20+) - HEADMAN T70M/1250 (720 mm swing, 117 mm bore, 3,000 rpm, BMT75 12-station turret). Made for shafts, bushings, flanges up to ±0.002 mm.
- Wire EDM (5+) - Sodick AQ535L (550/350/300 mm travel, ±20° taper, 800 kg workpiece). Made for hardened tool steel, internal splines, sharp internal corners that milling cannot reach.
- Inspection: Hexagon CMM + 20+ gauges - Hexagon CMM for coordinate measurement, plus vision system, profilometer, hardness tester, coating thickness gauge, XRF for material verification. The 10:1 rule (gauge 10x more accurate than the band) is applied to every feature.
- Machine highlights - VARIAXIS I-600: one-setup multi-face 5-axis + MAZA-CHECK auto-calibration; INTEGREX I-250H S: DONE-IN-ONE mill-turn, B-axis 0.0001° + Ai thermal shield; SPEEDIO S500Z2N / S700Z2N: Z-axis 2.2 G + 0.7 s ATC; Swiss-type: guide-bush switchable + 0.1 µm resolution.
Tolerance: ±0.003 mm CNC milling / ±0.002 mm CNC turning / ±0.002 mm grinding and wire EDM. Capability: Ppk >= 1.67 initial on key characteristics, Cpk >= 1.33 ongoing.
Certificates: ISO 9001:2015 (116024/A/0001/UK/En), IATF 16949:2016 (131941/A/0001/SM/En, with design clause 8.3 excluded, stated openly) and ISO 14001:2015 (116024/B/0001/UK/En), issued to Dongguan Zhuohang Ltd, registration 91441900MA4UWT6X39, founded 2005.
Where we ship: Austria, Belgium, the Czech Republic, Denmark, France, Germany, Greece, Hungary, Ireland, Italy, the Netherlands, Spain, Sweden and the United Kingdom in Europe; Brazil, Canada, Mexico and the United States in the Americas; China, Israel, Japan, Singapore and Sri Lanka in Asia; Australia and New Zealand in Oceania; and South Africa in Africa — plus other countries and regions worldwide, shipped from our base in Dongguan, China.
Contact: Felipe Iglesias, [email protected], +86 13126536955.
Not sure this is the right process?
Send the model and the drawing and get a straight answer on whether this route is the right one, including where a design change would cut cost. Reach Felipe Iglesias at [email protected] or +86 13126536955.
Frequently Asked Questions
Which markets do you export to?
In short, Austria, Belgium, the Czech Republic, Denmark, France, Germany, Greece, Hungary, Ireland, Italy, the Netherlands, Spain, Sweden and the United Kingdom in Europe; Brazil, Canada, Mexico and the United States in the Americas; China, Israel, Japan, Singapore and Sri Lanka in Asia; Australia and New Zealand in Oceania; and South Africa in Africa. Our service area also spans Europe, the Americas, Asia, Oceania and Africa — based in China, we serve customers worldwide.
What happens if the first article does not conform?
In short, The nonconformance is documented and the corrective action is agreed before any further parts are made. Whether the replacement cost sits with the plant or the customer depends on where the deviation came from, which is why the revision and the drawing standard are confirmed in writing at the start.
Do you certify aluminum material?
Yes. Material certificates are supplied with the parts and incoming stock is checked against the mill certificate — composition by XRF, hardness where specified. Traceability is per heat or per batch as the certificate defines it.
What is the difference between a prototype build and a production build here?
Usually only quantity and scheduling. Both run on the same machines and the same process, which is what makes a later ramp a scheduling change rather than a re-qualification.
What tolerances can you hold?
In short, ±0.003 mm on CNC milling, ±0.002 mm on CNC turning, and ±0.002 mm where precision grinding or wire EDM is used. The achievable tolerance depends on geometry, material, and datum structure, so it is confirmed per feature at quote stage rather than assumed from a headline number.
Does aluminum cost more to machine than aluminium?
Usually yes, and the reason differs by material: for titanium it is cutting speed and tool consumption, for stainless it is cycle time and work-hardening management. The lever that matters most is usually design depth rather than process choice.
Do you sign NDAs before reviewing drawings?
Yes — an NDA can be signed before any files change hands, and drawings stay inside the quoting system rather than circulating by email.
Continue reading: 3 Axis China CNC Machining · 4 Axis China CNC Machining · 5 Axis China CNC Machining
Standards referenced on this page
- ASTM B211/B211M-19 — Standard Specification for Aluminum-Alloy Rolled or Cold Finished Bar, Rod, and Wire
- ASTM A582/A582M-12 — Standard Specification for Free-Machining Stainless Steel Bars
- ISO 9001 — Quality management systems — Requirements