Service for CNC Aluminum Machined Parts for Sale
This guide is for engineers and purchasing teams comparing quoting options for machined aluminum parts. It covers the checks that separate a workable supplier from an expensive lesson: tolerance, alloy grade, lead time, MOQ and certifications.
In this article
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What matters before you order
Choosing a CNC aluminum machined parts for sale supplier
Use this table to score two or three quotes on the same rows.
| Criterion | What to ask | Good answer | Red flag |
|---|---|---|---|
| Tolerance | Which surfaces need ±0.005 mm? | They ask for a drawing review first | They quote ±0.005 mm on every face |
| Alloy grade | Do you stock 6061-T6 and 7075? | Mill certs provided with the parts | Grade listed as 'aluminum' only |
| Lead time | When do parts ship after PO? | 3–5 days for standard aluminum work | Verbal 'soon' with no date |
| MOQ | Can you run one prototype? | No minimum order quantity | Setup fee that doubles the unit price |
| Inspection | What is measured before shipment? | 100% inspection, reports on request | Sampling only, no report offered |
| Certification | Which certs are in scope? | ISO 9001, IATF 16949, ISO 13485 | Certificate expired or out of scope |
| Confidentiality | Will you sign an NDA? | NDA available on request | Refusal to sign before files are sent |
The short version
Pick the supplier who asks about your datums, shows you mill certs and quotes in 12 hours. Price matters, but a part that fits first time is cheaper than a rework loop.
Tolerance: where ±0.005 mm belongs
Every aluminum part has a few surfaces that matter and many that do not. A mounting face, a bearing bore, a dowel hole, a sealing groove. Those are the places where ±0.005 mm earns its cost. The rest of the part can usually sit at ±0.05 mm or looser and work just as well.
When a drawing calls tight tolerance on everything, two things happen. The shop spends more time on setups and in-process checks, and the quote goes up. Worse, tight tolerance on a non-critical face can pull the part out of alignment elsewhere because the machinist chases a number that does not affect function.
A useful first step is to mark the datum surfaces on your drawing. Tell the shop which features are functional and which are cosmetic or clearance. They can then plan the fixturing around those datums and leave the rest at general machining tolerance. That single change often cuts both cost and lead time.
For aluminum specifically, thermal movement matters. A 300 mm 6061 part grows about 0.007 mm for every 1 °C rise. If your inspection room sits at 20 °C and the machine shop runs at 26 °C, the same part measures differently in each place. Ask how the shop handles this. A good answer mentions temperature-controlled inspection or a soak period before final measurement.
- 1Call out datumsMark A, B and C on the drawing so fixturing follows function.
- 2Split the tolerance bands±0.005 mm on functional features, ±0.05 mm elsewhere.
- 3Ask about inspection temperatureAluminum moves with heat; measurement conditions matter.
Alloy grade and how it changes the cut
Aluminum is not one material. 6061-T6 is the default for machined parts: good strength, easy to cut, welds well, and stocked almost everywhere. 2024 cuts faster and is stronger in fatigue but corrodes more easily and is harder to weld. 7075 offers the highest strength of the common grades but is tougher on tooling and more prone to chipping on thin edges.
The choice usually comes down to the part, not the price. A bracket that sees vibration benefits from 7075. A housing that will be anodized and handled daily is fine in 6061. A heat sink or a panel that needs conductivity may be better in 5052 or 6063.
Ask the shop what they stock. A supplier who keeps 6061, 6061-T6, 2024, 5052, 5083, 6063, 6082, 7075 and ADC12 on the shelf can start production within 24 hours. If they have to order the billet, add days to the schedule before any chips are cut.
One more check: request the mill certificate with the parts. It confirms the heat lot, the temper and the chemistry. Without it, you are trusting a label. For aerospace, automotive and medical work, the cert is part of the record, not an optional extra.
- 16061-T6General purpose. Easy to machine, anodizes well, widely stocked.
- 27075High strength. Use where weight and stiffness drive the design.
- 32024Fatigue resistant. Watch corrosion and welding limits.
- 4ADC12Die casting grade. Relevant when the part may move to casting later.
Lead time, MOQ and how quotes are built
Lead time is not one number. It is quote time, material time, machining time and inspection time added together. A shop that quotes in 12 hours and starts production within 24 hours is telling you two things: they have capacity, and they have material on the floor.
Ask what happens after the first article. For a prototype run, the parts ship in 3–5 days in many aluminum jobs. For a 10,000-part run, the schedule depends on how many machines are assigned and whether secondary operations like anodizing are in-house or outsourced. Get the milestone dates in writing.
MOQ is the other half of the equation. Some suppliers will not quote below 100 pieces, which makes design iteration expensive. A shop with no minimum order quantity lets you run one prototype, check the fit, then scale. That flexibility is worth more than a few cents off the unit price on a part that is still changing.
When you compare quotes, put them on the same footing. Ask for material cost, setup cost and unit cost separately. A low unit price with a large setup fee is not cheaper for a small run. It only looks cheaper until you read the second page.
- 1Quote within 12 hoursIncludes free DFM analysis on the drawing.
- 2Production within 24 hoursRealistic when material is already in stock.
- 3Parts ship in 3–5 daysTypical for standard aluminum work without exotic finishing.
- 4No minimum order quantityFrom one prototype to 10,000+ part runs.
Certifications, inspection and what they actually cover
Certificates are not interchangeable. ISO 9001:2015 is a general quality management standard. It says the shop has a documented process, not that it can hold a specific tolerance on your part. IATF 16949:2016 adds automotive requirements like traceability and change control. ISO 13485:2016 is the medical device equivalent. ISO 27001:2022 covers information security, which matters if your drawings are sensitive.
Read the scope statement on each certificate. A shop can hold a certificate that excludes the process you need. If the scope covers machining but not finishing, the anodized surface on your part is outside the audited system.
Inspection is where the certificate meets the part. Look for raw material check, in-process monitoring and final inspection before shipment. Ask whether inspection is 100% or sampled. For functional aluminum parts, 100% inspection with reports on request is the safer default.
Request the inspection report format before you place the order. First article inspection reports, dimensional reports and material certs should be something the shop produces routinely, not something you have to negotiate after the parts are made.
- 1ISO 9001:2015General quality system. Baseline for most buyers.
- 2IATF 16949:2016Automotive. Adds traceability and change control.
- 3ISO 13485:2016Medical devices. Process validation focus.
- 4ISO 27001:2022Information security. Relevant for confidential drawings.
Surface finish and secondary operations
Machining leaves tool marks. How visible they are depends on the finish you specify. As-machined aluminum typically sits at Ra 1.6–3.2 μm. A high-quality cosmetic finish lands around Ra 0.8–1.6 μm. Fine finishes at Ra 0.2–0.8 μm take longer and cost more, and they are usually only needed on sealing surfaces or optical mounts.
Anodizing is the most common aluminum finish. Clear anodizing keeps the metal look and adds wear resistance. Color anodizing introduces batch-to-batch variation, so if you need a color match across two orders, say so upfront. Hardcoat anodizing builds a thicker oxide layer for wear surfaces. Conductive anodizing is used where the part must still ground.
Other options include electroless nickel, zinc, silver and gold plating, powder coating and black oxide. Bead blasting, tumbling, brushing and polishing change the texture before any coating goes on. Laser marking and engraving need a minimum character height of 1.5 mm to stay legible.
The trap here is ordering finishing as an afterthought. If the anodizer is a separate company, your parts leave the machine shop and come back on someone else's schedule. Ask whether finishing is handled in-house or coordinated, and build that time into the plan.
- 1As-machinedRa 1.6–3.2 μm. Fine for hidden or non-cosmetic faces.
- 2High-quality finishRa 0.8–1.6 μm. Visible parts and mating surfaces.
- 3Fine finishRa 0.2–0.8 μm. Sealing faces and precision fits.
- 4Anodizing typesClear, color, hardcoat and conductive each solve a different problem.
How to vet a supplier in six steps
Work through these in order. Each one removes a category of risk.
- 1Send the drawing and a target quantityInclude the STEP file, the 2D drawing with GD&T, and the alloy grade. Note which features are functional. Ask for a quote and a DFM review within 12 hours.
- 2Read the DFM feedback, not just the priceA useful DFM note flags thin walls, deep pockets, tight radii and features that need a second setup. If the feedback is generic, the shop may not have looked at the part.
- 3Ask for material certificates upfrontConfirm the grade and temper match the drawing. For 6061-T6, the T6 temper is a heat treatment step, not a label. The mill cert proves it.
- 4Confirm the inspection planAsk what is measured, on which features, and whether the report is included. For functional parts, 100% inspection before shipment with reports on request is the standard to hold.
- 5Run one prototype before committing to volumeWith no minimum order quantity, a single part is a cheap way to check fit, finish and tolerance before you release a 10,000-part order.
- 6Lock the schedule and the paperworkGet the ship date, the finishing plan and the NDA in place before the PO. Uploads should be secure and confidential, with an NDA available on request.
Questions buyers ask before ordering
Can you hold ±0.005 mm on a large aluminum part?
Yes, on the features that need it. A 4,000 mm maximum processing size is available, and 5-axis centers with a Ø400 mm rotary table handle contoured work.
The practical limit is thermal. Long aluminum parts move with temperature, so we soak and measure in a controlled environment before final inspection.
What is the smallest order you accept?
There is no minimum order quantity. We run from one prototype to 10,000+ part runs.
For a single part, the setup cost dominates the price. Send the drawing anyway; the DFM feedback alone is often worth the quote.
Which aluminum grades do you keep in stock?
6061, 6061-T6, 2024, 5052, 5083, 6063, 6082, 7075 and ADC12.
Stocked material is what allows production to start within 24 hours. If your grade is not on the list, ask; we will tell you the added lead time before you commit.
How do you handle confidential drawings?
Uploads are secure and confidential, and we hold ISO 27001:2022 for information security. An NDA is available on request.
Send the NDA before the files if your process requires it. We can sign first.
Do you provide inspection reports?
Yes, on request. The standard flow is raw material check, in-process monitoring and final inspection, with 100% inspection before shipment.
Tell us the report format you need at quoting stage so it is built into the plan rather than added at the end.
What finishes can be applied to aluminum parts?
Anodizing in clear, color, hardcoat and conductive types; electroless nickel, zinc, silver and gold plating; powder coating and black oxide; plus bead blasting, tumbling, brushing, polishing and laser marking.
Laser marking needs a minimum character height of 1.5 mm. Anything smaller may not read cleanly after anodizing.
Send your aluminum drawing today
Upload a STEP file and 2D drawing for a quote with free DFM analysis within 12 hours. No minimum order quantity, 100% inspection before shipment.
12-hour quoteNo MOQ100% inspection
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We publish setup notes, tooling trials and inspection data from the factory floor.
