Custom CNC Brass Machining Part Service
A guide for engineers and sourcing managers who are choosing a supplier for custom CNC brass parts. It covers alloy grade, tolerance bands, finish options, lead time and the checks that separate a shop that holds ±0.005 mm in production from one that only holds it on the first sample.
In this article
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Key takeaways
Brass grades compared for CNC machining
Machinability is rated against C36000 at 100%.
| Grade | Machinability | Typical parts | Watch out for |
|---|---|---|---|
| C36000 | 100% | Fittings, bushings, valve bodies | Lead content; not for potable water |
| C27400 | 70% | Forged or machined hardware | Longer cycle time than C36000 |
| C28000 | 60% | Couplings, decorative parts | Gummy chips; needs sharp tools |
| C110 | 30% | Bus bars, electrical contacts | Sticky chips, poor chip break |
| C101 | 25% | High-conductivity electrodes | Not for tight tolerances |
| Beryllium copper | 40% | Spring contacts, non-sparking tools | Beryllium dust needs extraction |
Brass finishes and what they cost you in process
| Finish | Effect on size | Best for | Notes |
|---|---|---|---|
| Bare, tumbled | None | Parts used indoors within weeks | Tarnishes fast in humid air |
| Clear lacquer | 2–5 μm | Decorative and display parts | Can blister if surface is oily |
| Electroless nickel | 8–15 μm | Wear surfaces, connectors | Threads must be cut undersize |
| Silver or gold plating | 3–8 μm | RF and electrical contacts | Specify thickness per surface |
| Bead blasting | Removes 2–5 μm | Matte cosmetic finish | Rounds sharp edges; deburr first |
| Brushed or polished | Removes 5–20 μm | Visible consumer parts | Hand operation; cost scales with area |
When to pick a brass-focused shop
Choose a supplier who runs Swiss-type lathes and mill-turn centers, quotes tolerances per feature and sends the mill certificate with the parts. If the quote is far below the others and the grade is not named, walk away.
What actually makes a custom CNC brass part order go wrong
Most brass machining problems trace back to two decisions made before the first chip is cut: the alloy grade and the tolerance callout. Brass machines easily, which is exactly why buyers stop paying attention. A part quoted in C36000 at ±0.005 mm and then switched to C28000 to save material cost will not hold that band on a production run, because the gummy chip pulls the tool and the finished diameter drifts.
Geometry matters just as much. A turned bushing with a 12 mm bore is a straightforward job on a Swiss-type lathe. The same part with a 0.8 mm wall and a 0.5 mm cross-hole needs a second operation, a fixture and a deburring step. Those costs are real, and a quote that ignores them is a quote that will change later. Ask the shop which operations it priced.
The third common failure is finish. Brass responds well to tumbling, brushing and polishing, but it tarnishes in weeks if it is left bare and handled. If the part will sit in inventory or ship by sea, specify a clear lacquer, electroless nickel or a chromate-free passivation and say so on the drawing.
- 1Free-cutting gradesC36000 and C27400 give the best chip control on automatic lathes.
- 2Conductive gradesC101 and C110 are for electrical function, not for tight tolerances.
- 3Thin wallsBelow 1 mm wall, expect a second operation and a fixture.
How to read a tolerance and inspection claim
±0.005 mm is a real number on a well-set CNC lathe, but it does not apply to every feature on the drawing. Turned diameters, bores and ground faces can hold it. Milled pockets, slot widths and cross-drilled holes usually land between ±0.013 mm and ±0.025 mm because the tool deflects and the setup has more variables. A supplier who quotes one blanket tolerance for the whole part is either overpromising or pricing in a lot of scrap.
Ask how the shop inspects. For brass, the practical stack is a micrometer and bore gauge for diameters, a CMM for position and true position callouts, and a profilometer for Ra. We run raw material checks, in-process monitoring and a final inspection, and we inspect 100% of parts before shipment. Reports are available on request, and for medical or automotive work the report package is part of the deliverable, not an extra.
Qualification rate is the number that matters more than the tolerance on the quote. A shop that holds 99.99% of parts within specification is running tight process control. A shop that holds 97% will ship you the same parts, but you will find the rejects at your incoming inspection, and that cost lands on you.
- 1Turned features±0.005 mm is achievable on diameters and bores.
- 2Milled featuresPlan on ±0.013 mm to ±0.025 mm unless you pay for a finishing pass.
- 3Surface finishRa 0.8–1.6 μm is the standard machined finish; Ra 0.2–0.8 μm needs a polishing step.
- 4Inspection recordAsk for the sample size, not just the word 'inspected'.
Five checks before you release a brass order
First, confirm the plant. A supplier with several sites should tell you which one will cut your parts, because that determines the equipment, the certificate scope and the lead time. We run three wholly-owned plants, including a factory at No.3 Joo Koon Circle, Singapore 629032, alongside the Dongguan operation. If your project needs a specific site, say so in the RFQ.
Second, confirm the machine. Brass parts under 32 mm diameter belong on a Swiss-type lathe or a mill-turn center, not on a 3-axis mill with a vise. We run 127 high-precision CNC machines, including 16 simultaneous 5-axis machining centers and 16 mill-turn centers. The right machine class is what keeps the cycle time and the tolerance stable across a run.
Third, confirm the material certificate. Ask for the mill certificate with the heat number and check that the grade matches the drawing. Substituting C36000 with a generic 'brass' is common in low-cost quotes and it changes the machinability, the strength and sometimes the lead content.
Fourth, confirm the finish and the packaging. Brass scratches easily and tarnishes. Tumbled, deburred parts shipped loose in a bag will arrive with edge damage. Specify the finish, the tarnish protection and the packaging method in the purchase order.
Fifth, confirm the data handling. If your drawings are proprietary, an NDA should be signed before files are uploaded. We keep uploads secure and confidential, and an NDA is available on request.
- 1Plant locationName the site in the RFQ, not after the order.
- 2Machine classSmall turned brass parts belong on a Swiss-type lathe.
- 3Mill certificateHeat number plus grade, matched to the drawing.
- 4NDA firstSign before uploading drawings, not after.
How lead time and price are actually built
Lead time on a brass part is set by three things: programming and setup, material availability and finishing. Programming and setup for a new part is typically one to two days. If the grade is in stock, production can start within 24 hours of the order. Parts ship in 3–5 days for standard quantities. When a part needs plating or anodizing, add the outside process time, which is usually the longest single step in the chain.
Price follows the same logic. The material is a small share of a machined brass part; the setup, the cycle time and the inspection dominate. That is why a 100-piece order and a 10,000-piece order have very different unit prices, and why a one-piece prototype is expensive per unit but cheap in absolute terms. We have no minimum order quantity, so a single prototype and a 10,000+ part run are both normal work.
Beware of a quote that is far below the others. On brass, the usual causes are a substituted grade, a looser tolerance than the drawing calls for, skipped deburring, or a shop that has not priced the fixture. Ask for the grade, the tolerance per feature and the inspection plan in writing. A supplier who cannot answer those three questions is not a supplier you want on a production part.
- 1Quote turnaroundQuotation and free DFM analysis within 12 hours.
- 2Production startWithin 24 hours once material is confirmed.
- 3ShippingStandard brass parts ship in 3–5 days.
- 4FinishingAdd outside process time; it often dominates the schedule.
Step by step: from drawing to shipped brass parts
- 11. Send the 3D model and 2D drawingInclude the material grade, the tolerance per feature, the finish and the critical dimensions. STEP plus PDF is enough to start. Uploads are kept confidential and an NDA is available on request.
- 22. Review the DFM reportWe return a quotation and a free DFM analysis within 12 hours. Check for wall thickness below 1 mm, sharp internal corners that need a smaller cutter, and deep pockets that need a long-reach tool.
- 33. Lock the grade and the tolerance calloutConfirm C36000, C27400 or C28000 against the mill certificate. Split the tolerance callouts into turned and milled groups so the quote reflects what each feature can actually hold.
- 44. Approve the first articleFor a new part, review the first article before the run continues. Check the critical dimensions on a CMM report and confirm the surface finish with a profilometer.
- 55. Confirm the finish and packagingDecide between bare tumbling, lacquer, electroless nickel and plating. If threads are present, cut them undersize so the coating does not close the pitch diameter.
- 66. Run production with in-process checksProduction starts within 24 hours of material confirmation and ships in 3–5 days. In-process monitoring catches tool wear before it pushes a diameter out of band.
- 77. Final inspection and documentation100% inspection before shipment, with raw material, in-process and final reports on request. Review the report against your drawing before releasing the shipment to your line.
Questions buyers ask about brass CNC parts
Which brass grade is best for CNC machining?
C36000 free-cutting brass is the default for turned parts. It has the best machinability of the common grades, produces short chips and holds tight diameters well. C27400 is a close second and is often chosen where a slightly higher strength is useful.
C110 and C101 copper are chosen for electrical conductivity, not for machining. They produce sticky chips and are harder to hold to tight tolerances, so use them only when the electrical function requires it.
Can you hold ±0.005 mm on brass parts?
Yes, on turned diameters and bores, and on ground faces. That tolerance is achievable on a well-maintained CNC lathe with the right tooling and a stable setup.
It does not apply to every feature. Milled pockets, slot widths and cross-holes typically land between ±0.013 mm and ±0.025 mm. We quote tolerances per feature so the price reflects what the process can actually deliver.
Is there a minimum order quantity?
No. There is no minimum order quantity. A single prototype and a 10,000+ part run are both normal work, and both go through the same inspection process.
Unit price drops with volume because setup and programming are spread over more parts, not because the process changes.
How fast can brass parts ship?
Quotation and free DFM analysis come back within 12 hours of receiving a complete drawing package. Production can start within 24 hours once material is confirmed, and parts ship in 3–5 days.
If the part needs plating, anodizing or another outside finish, add that process time. Finishing is usually the longest single step in the schedule.
Do you sign an NDA before I upload drawings?
Yes. Uploads are secure and confidential, and a non-disclosure agreement is available on request. We can sign yours or provide ours before any files are transferred.
We are certified to ISO 27001:2022 for information security, alongside ISO 9001:2015, IATF 16949:2016 and ISO 13485:2016.
What causes brass parts to fail incoming inspection?
The three most common causes are a substituted alloy grade, a tolerance band that is tighter than the process can hold on a milled feature, and handling damage from loose packaging.
Ask for the mill certificate with the heat number, split the tolerance callouts by feature type, and specify the packaging. Those three steps remove most incoming rejections on brass work.
Send your brass drawing and get a quote in 12 hours
Upload the STEP file and the 2D drawing. We return a quotation with a free DFM analysis within 12 hours, and an NDA is available before you send anything.
12-hour quoteNo MOQ100% inspectionNDA on request
More from the shop floor
We publish setup notes, tooling trials and inspection data from the factory floor.
