A working library of CNC machining articles written by process engineers. Tolerances, stainless steel milling, milling versus turning, prototyping cost drivers, and how to read a supplier quote before you commit tooling.
Most CNC failures trace back to a decision made before the spindle turned.
A drawing marked ±0.1 mm on a 300 mm aluminium bracket is easy. The same callout on a thin wall will move after clamping and heat. We see parts scrapped because the tightest tolerance was applied to the least critical feature. Sorting out which dimensions actually drive function saves money and rework.
304 and 316 work-harden the moment the tool rubs instead of cuts. Feed too light and the surface gets harder under the insert, then the next pass chips the edge. A 316 housing that should run at Ra 1.6 μm comes out torn, and you spend the afternoon re-cutting a feature that was already in tolerance.
A low prototype price often means the fixture was skipped. The first five parts look fine. By part twenty the position drifts, and the operator is shimming the vise. What looked like a cheap prototype turns into a second setup and a second invoice.
A turned part quoted as a mill job can cost three times more than it should. Round features belong on a lathe. Prismatic pockets belong on a mill. When the process is chosen after the quote instead of before, the price does not hold.
Sixteen simultaneous 5-axis centers, 16 mill-turn centers, and 127 machines in total give us room to pick the right process instead of the nearest one.
Turned shafts, bushings, and threaded connectors go on a lathe. Housings with pockets and bolt patterns go on a mill. Parts that need both in one setup go on a mill-turn center, which holds concentricity between the bore and the outside diameter without a second op.
That decision is made from the 3D file, not from a category label. A part with a Ø12 mm bore through a 200 mm body is a lathe part. The same body with two offset slots is a mill-turn part. Getting this right at the quote stage removes the rework that shows up later.
±0.005 mm is achievable on a well-supported feature with a stable setup. It is not a default. Applying that band across a whole drawing raises cost without improving function, because the tightest callout sets the inspection plan for the entire part.
Surface finish follows the same logic. Ra 0.2–0.8 μm needs a finishing pass with a sharp tool and a rigid setup. Ra 1.6–3.2 μm is fine for most structural faces and costs less to produce. We flag where a tighter finish adds nothing, and where it is the only way to make a seal work.
A quick reference for the geometry that decides the machine.
| Part type | Best process | Why |
|---|---|---|
| Turned shaft, bushing | CNC turning or mill-turn | Round geometry, single datum |
| Housing with pockets | 3-axis or 5-axis mill | Prismatic faces, bolt patterns |
| Impeller, turbine blade | 5-axis simultaneous | Compound angles, no re-fixture |
| Thin-wall aluminium cover | 3-axis with soft jaws | Controlled clamping, less deflection |
| Small connector body | Swiss-type turning | Long slender part, low deflection |
| Bore plus offset slots | Mill-turn center | Concentricity held in one setup |
Each route has its own machine group, its own fixtures, and its own inspection plan.
Simultaneous 5-axis for contoured surfaces, impellers, and housings that would need four setups on a 3-axis machine. Sixteen centers available.
Rotary table work for parts with features on several faces. Twelve four-axis mills with a Ø400 mm rotary table.
The workhorse for prismatic parts, plates, and covers. Twenty-seven machines for flat geometry and drilling patterns.
Sixteen mill-turn centers handle parts that need turning and milling in one setup, holding concentricity without a second chuck.
One-off and low-volume parts for fit checks and design review. Useful before committing to a production fixture.
Anodizing, plating, bead blasting, and laser marking. Finish chosen for corrosion, wear, or appearance.
| Capability | Range | Typical use |
|---|---|---|
| Maximum part size | 4,000 mm | Long rails and structural beams |
| Large travel | 4,000 × 400 × 150 mm | Elongated parts, single setup |
| Medium travel | 750 × 1,150 × 550 mm | Housings and manifolds |
| Compact travel | 500 × 500 × 450 mm | Small precision components |
| Rotary table | Ø400 mm | Multi-face parts in one op |
| Tolerance | ±0.005 mm | Critical fits and bores |
The numbers behind the work, not a list of adjectives.
Three wholly-owned plants and 150 technicians. The process knowledge comes from parts that shipped, not from a catalogue.
On supported features with a stable setup. We tell you when a tighter band adds cost without improving function.
Raw material check, in-process monitoring, and final inspection. Reports available on request.
Quotation and free DFM analysis within 12 hours. Production can start within 24 hours of approval.
Parts ship in 3–5 days for standard runs. Historical late-delivery probability stays below 2%.
One prototype or a 10,000+ part run. There is no minimum order quantity to cross.
Thin-wall aluminium brackets with compound angles. Material traceability from the mill certificate.
Aluminium and steel housings that carry sealing faces and bolt patterns. IATF 16949 process control.
316L and titanium parts with clean internal radii. ISO 13485 documentation and 100% inspection.
Joint housings and end-effector plates that need matched bores across a batch. Bore-to-bore position held on a mill-turn center.
±0.005 mm is achievable on a supported feature with a rigid setup and a stable material. That is not the same as holding it across every dimension on the drawing.
For most structural faces, ±0.05 mm is enough and costs less to inspect. We look at which dimensions control fit, sealing, or function, and put the tight band there.
304 and 316 work-harden when the tool rubs instead of cutting. A light feed leaves the surface harder than the base metal, and the next pass breaks down the insert edge.
The fix is a heavier feed per tooth, a sharp positive-rake insert, and enough coolant to clear the chip. On a deep pocket we sometimes rough with a larger tool and finish with a smaller one to keep the radial engagement steady.
If the primary geometry is round and concentric, it is a turning job. Shafts, bushings, and threaded bodies belong on a lathe.
If the part is prismatic with pockets and bolt patterns, it is a mill job. When both are present, a mill-turn center handles it in one setup, which holds concentricity and removes the re-chuck error that shows up on a second op.
Setup and fixturing usually cost more than the cutting time on a one-off part. A simple vise setup is cheap. A custom soft-jaw fixture or a 5-axis setup with a tombstone adds hours before the first chip.
Material also matters. A 7075 aluminium block costs more than 6061, and titanium or Inconel cut slower and wear tools faster. Tight tolerances and fine finishes add inspection and finishing time on top.
No. We return a quotation and a DFM analysis within 12 hours, and the analysis points out features that will be hard to hold, thin walls that may deflect, and tolerances that can be relaxed without affecting function.
You can use that feedback to revise the design before any material is cut.
Uploads are kept secure and confidential. We can sign an NDA before you send the files if your process requires it.
NDA available on request, and it covers the drawings, the model, and any process notes we produce.
Anodizing in clear, colour, hardcoat, and conductive grades. Electroless nickel, zinc, silver, and gold plating. Powder coating, black oxide, bead blasting, tumbling, brushing, and polishing.
Pick by function. Hardcoat anodizing for wear surfaces, electroless nickel for corrosion and solderability, bead blasting for a matte cosmetic face. Laser marking is available down to 1.5 mm character height.
Production can start within 24 hours of approval on a released model. For parts that are still moving, we usually recommend a small prototype run first so the geometry is settled before fixtures are built.
Once the model is frozen, the same machine group that ran the prototype runs the production parts.
Quotation and free DFM analysis within 12 hours. No minimum order quantity, from one prototype to a 10,000+ part run.
12-hour quote100% inspectionNo minimum order quantityNDA on request
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Upload your 3D model or 2D drawing and get a quotation with a free DFM analysis. Maximum processing size 4,000 mm.
CNC Metals 13 grades
CNC Plastics 10 grades
Machines & processes 12 options
Surface & post-processing 10 options
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