Reference notes from a shop that runs 127 CNC machines. Material picks, cutting data, finishing choices and tolerance limits — written for engineers who have to commit to a drawing.
Four situations that cost time and parts. Each one is cheaper to fix on paper than on the machine.
A part designed around 6061 gets quoted in 7075 for strength. Now the tool load is higher, the finishing pass is slower, and thin walls move after heat treat. We catch it in DFM review, not after the first article.
A ±0.005 mm callout on a non-critical bolt hole doubles cycle time and inspection cost. Roughly half of the tight tolerances we see on incoming drawings do not affect function.
Someone wrote Ra 0.4 μm on a bracket that only needs to not cut hands. That is a second operation, a different wheel, and a slower spindle. Ra 1.6–3.2 μm is as-machined and often enough.
A 3-axis quote turns into four setups, four fixtures and a stack-up of positional error. Sometimes the fix is one drawing change. Sometimes the part needs 5-axis work, and the quote should say so up front.
Two things matter on a machined part: the material callout and the process that produces it. We publish what we know from both sides.
Most aluminum parts we quote land on 6061-T6. It machines clean, welds, anodizes well, and holds ±0.005 mm on a rigid setup. Switch to 2024 only when fatigue strength or yield matters more than corrosion resistance and finish. Switch to 7075 when the part is a load path and weight is fixed.
Stainless is where drawings get expensive. 303 is free-machining and good for shafts and fittings. 304 is tougher, galls more, and needs sharper tools and lighter cuts. 316 and 316L go to medical and marine work. 17-4PH (SUS630) buys you strength after aging, but plan the heat treat before the finish.
Titanium and Inconel are a different budget. TC4 (Ti-6Al-4V) needs slow speeds, high coolant pressure and sharp tooling. Heat does not leave the cut zone. If a design can be done in 6061 with a thicker section, that is usually the cheaper answer.
A 3-axis mill handles flat plates, pockets and drilled holes from one face. Add a fourth axis and you cut four faces in one setup, which removes a fixture and a re-datum. Our 5-axis centers exist for parts with compound angles, deep cavities and tight true position between features on different faces.
The limit is usually not the control, it is the reach. We run 4,000 × 400 × 150 mm travel on the large machines, 750 × 1,150 × 550 mm and 600 × 600 × 600 mm in the middle, and 500 × 500 × 450 mm or 500 × 310 × 200 mm on the compact frames. A Ø400 mm rotary table covers round and index work.
If a feature cannot be reached without a long tool, we say so at quote. A long tool deflects, and deflection shows up as taper and chatter, not as a number on the drawing.
A short version of the decision we make on incoming drawings.
| Alloy | Good for | Watch out for |
|---|---|---|
| 6061-T6 | Brackets, housings, fixtures, anodized parts | Softer than 7075 under high point load |
| 2024 | Fatigue-loaded aircraft parts | Poor corrosion resistance without coating |
| 5052 / 5083 | Sheet, tanks, marine, formed parts | Not a high-strength machining alloy |
| 7075 | Load paths, molds, weight-critical parts | Higher tool wear, harder to weld |
| 303 stainless | Shafts, fittings, high-volume turning | Lower corrosion resistance than 304 |
| 316L | Medical, marine, chemical exposure | Galls easily, slower cycle times |
| 17-4PH | High-strength shafts and valves | Strength comes only after aging |
| TC4 (Ti-6Al-4V) | Aerospace and implant-grade parts | Slow cutting, heat stays in the tool |
| POM / PEEK | Insulators, bushings, low-friction parts | Thermal growth, fixturing marks |
One supplier for the metal cut, the surface treatment and the inspection report.
Compound angles, contoured surfaces and multi-face features in one setup. 16 simultaneous 5-axis centers.
Plates, pockets, housings and index work. 27 three-axis and 12 four-axis machines.
Mill-turn centers handle turned parts with cross features and no second op.
One-off and low-volume parts to check fit before tooling money is spent.
Brackets, enclosures and panels when the part is flat and the volume is higher.
Anodizing, plating, powder coating, black oxide, bead blasting and laser marking.
Numbers we can hold, stated plainly.
| Item | Capability | Notes |
|---|---|---|
| General tolerance | ±0.005 mm (±0.0002 in) | On rigid setups with stable material |
| Fine finish | Ra 0.2–0.8 μm | Extra pass, slower spindle |
| High finish | Ra 0.8–1.6 μm | Common for sealing faces |
| As-machined | Ra 1.6–3.2 μm | Enough for most brackets |
| Max part size | 4,000 × 400 × 150 mm | Large travel frames |
| Mid-size travel | 750 × 1,150 × 550 mm | General milling work |
| Rotary work | Ø400 mm rotary table | Indexed and contoured turning |
| Laser marking | 1.5 mm minimum character height | Legible after anodizing |
| Volume | 1 part to 10,000+ | No minimum order quantity |
Six things that decide whether a job ships clean or ships twice.
Three wholly-owned plants and 7,600 m² of floor space, so a job does not sit waiting for a slot.
16 five-axis centers, 16 mill-turn centers, 12 four-axis mills and 27 three-axis machines.
Held on turned and milled features where the setup and material allow it.
Drawing review, material note and a manufacturability comment inside 12 hours.
Production can start within 24 hours of an approved order.
Raw material check, in-process monitoring and final inspection, with reports on request.
Traceable material, tight true position on multi-face parts, documented inspection.
Stable alloy callouts for housings and brackets, finish that survives coating.
Clean deburring, no cross-contamination on 316L, inspection records on file.
Repeatable mounting faces so arms and actuators align without shimming.
No. Tight tolerances on non-functional features raise cycle time, tool cost and inspection time without improving the part. Put tight limits on the features that locate, seal or mate, and leave the rest at general tolerance.
If you are not sure which features matter, send the drawing. The DFM note will say where the tight callout is doing work and where it is only adding cost.
6061-T6 covers most brackets, fixtures and housings. It machines fast, anodizes clean and holds tolerance without drama.
Go to 7075 when the part carries a real load and you cannot add section thickness. Expect shorter tool life and less forgiving chatter behavior. It is not a corrosion part without coating.
When features on different faces must hold true position to each other and refixturing would stack error. Compound angles and contoured pockets also point to 5-axis.
For flat plates with holes on one face, 3-axis is cheaper and just as accurate. We quote the process the geometry needs, not the one with the better name.
Give a number on the faces that matter, such as a sealing face at Ra 0.8–1.6 μm, and leave the rest as-machined at Ra 1.6–3.2 μm. A blanket fine-finish callout adds a second pass over the whole part.
Decorative finishes are separate. Anodizing, powder coating and black oxide change appearance and wear resistance but not the underlying surface roughness.
Anodizing in clear, color, hardcoat and conductive versions, electroless nickel, zinc, silver and gold plating, powder coating, black oxide, bead blasting, tumbling, brushing and polishing.
Laser marking and engraving run with a 1.5 mm minimum character height. Below that, marking on an anodized surface loses legibility over time.
Yes. There is no minimum order quantity, and the same machines run one-off parts and 10,000+ part runs. Prototype work often goes through the sample center before production.
The quote includes a DFM analysis at no charge, so a prototype that cannot be machined as drawn gets flagged before metal is cut.
Uploads are kept secure and confidential. An NDA is available on request before files change hands, and it covers the drawing, the process notes and the inspection data.
We do not publish customer names or part photos without written permission.
Quotation and DFM feedback come back within 12 hours. Production can start within 24 hours of approval, and parts typically ship in 3–5 days depending on finish and quantity.
Historical late-delivery probability is below 2%. We would rather quote a longer window than promise a date the finishing line cannot hold.
Upload a STEP or PDF file and we return a quote, a material note and a DFM comment within 12 hours. No minimum order quantity.
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CNC Metals 13 grades
CNC Plastics 10 grades
Machines & processes 12 options
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