Reference notes for machinists and engineers: which alloys are magnetic, how 6061 and 7075 behave at the spindle, and what finish to specify. Written from the shop floor, not from a catalog.
Most of the questions below cost money when they are answered late.
7075 machines beautifully and finishes bright, then cracks at the weld or corrodes at a fastener interface. The material choice was made from a chart, not from the drawing's loading. Rework means restarting the part.
Annealed 304 is nearly non-magnetic. Cold work from turning, thread rolling, or bending shifts it enough that a reed switch or a magnetic sensor starts reading the part. The fix is usually 316L or a redesign, not a tighter tolerance.
Anodizing a part that already passed final inspection adds a 5–20 μm build on every surface, including the thread flanks and dowel bores. If the finish was not in the model from the start, the assembly no longer fits.
A ±0.005 mm bore across a 400 mm length is not a lathe problem, it is a fixturing and thermal problem. Quoting it without a process review puts the whole order at risk before the first chip is cut.
Material behavior, finish build, and process limits, explained with numbers.
A magnet is a quick check on any incoming bar stock. Aluminum, copper, brass, and austenitic stainless in the annealed state do not hold a magnet. Carbon steel, 400-series stainless, and any cold-worked austenitic grade will. That single test catches mixed material before it reaches the spindle.
The harder case is when a part has to stay non-magnetic after machining. Turning and thread rolling cold-work the surface, so 304 can pick up enough permeability to trip a sensor. For those parts we go to 316L with a passivation step, or to titanium and aluminium if the load allows it.
6061-T6 cuts clean at high spindle speed, welds, anodizes evenly, and holds a thread without drama. For brackets, housings, and anything that will be welded or hardcoated, it is the default for good reason. The ceiling is strength: about 276 MPa yield.
7075-T6 roughly doubles that yield strength, which is why it shows up in airframe fittings and high-load linkages. It also chips differently, work-hardens at the cutter, and does not weld. Anodizing it needs care because the copper content darkens the coating and can leave it brittle at sharp corners. Pick 7075 for stiffness and load, not because it machines faster.
Use this when the drawing leaves the grade or finish open.
| Decision | Pick this | Watch out for |
|---|---|---|
| Non-magnetic housing | 316L, 6061, brass | Cold-worked 304 turns magnetic |
| High load, no weld | 7075-T6 | No welding, harder on tooling |
| Weldment bracket | 6061-T6, 5052 | Not 7075 or 2024 |
| Mirror polish | 6063, 6061 | Soft alloys gouge easily |
| Corrosion plus load | 17-4PH, 316L | Heat treat before finish |
| Cheap prototype | 6061, ABS | Check tolerance before finish |
| Tight bore, long part | Stress-relieved 4140 | Machining stress moves the bore |
One shop for the prototype and the production run.
16 simultaneous 5-axis centers handle contoured faces, deep pockets, and features that would need three setups on a 3-axis machine.
27 three-axis mills, 12 four-axis mills, and 16 mill-turn centers cover prismatic parts and turned parts down to a Ø400 mm rotary table.
From a single prototype to 10,000+ part runs, with no minimum order quantity and production starting within 24 hours.
Brackets, enclosures, and chassis work that pair with machined inserts and need consistent bend allowances.
Anodizing, plating, powder coating, bead blasting, brushing, and laser marking with a 1.5 mm minimum character height.
Plastic and carbon-fibre parts for fit checks and fixtures before the machined version is cut.
Numbers straight from the floor.
| Item | Range | Notes |
|---|---|---|
| Maximum part size | 4,000 mm | Largest travel 4,000 × 400 × 150 mm |
| Standard travels | 750 × 1,150 × 550 mm | Also 600 × 600 × 600 mm |
| Tolerance | ±0.005 mm | ±0.0002 in on qualified features |
| Fine finish | Ra 0.2–0.8 μm | As-machined is Ra 1.6–3.2 μm |
| Materials | Al, steel, stainless | Plus titanium, Inconel, brass, plastics |
| Inspection | 100% before shipment | Reports on request |
| Qualification rate | 99.99% | In-process monitoring plus final check |
The reasons that show up in a first-article report.
Three wholly-owned plants and 150 technicians, with the process knowledge that comes from running the same alloy families for years.
Milling, turning, mill-turn, and 5-axis capacity in one plant means fewer handoffs and one inspection record for the whole order.
Send a model and get a quotation plus a free DFM analysis back within 12 hours, including callouts on features that will not hold.
Once the drawing and finish calls are locked, material is issued and the first setup goes on the machine the next day.
Raw material check, in-process monitoring, and final inspection on every order. Measurement reports on request.
One prototype or 10,000+ parts, quoted on the same process plan so the production run matches the sample.
Housings and brackets that must hold position through heat cycles and vibration.
Non-magnetic 316L and titanium parts with clean, burr-free edges and documented material.
Linkages and end-effector plates in 7075 where stiffness drives the design.
Large 4,000 mm frames and weldments that need flatness after machining.
No. Aluminum and its alloys are paramagnetic, which means they respond to a magnetic field only microscopically and will not hold to a magnet.
That is one reason aluminum housings are used around magnetic sensors and reed switches. If a part must be non-magnetic, 6061, 6063, 2024, and 7075 all qualify.
Commercially pure titanium and Ti-6Al-4V are both non-magnetic in practice. They will not stick to a magnet.
The exception is contamination. Titanium that has picked up iron from tooling or handling can show a weak pull. Clean the part and re-test before you reject it.
No. Copper, brass, and bronze are non-magnetic, which is why C101, C110, and C36000 are common around electrical and sensor assemblies.
Beryllium copper is also non-magnetic after the usual heat treatment, though it costs far more and needs its own handling rules.
Carbon steel and most alloy steels are strongly magnetic. That covers 1018, 1045, 4130, 4140, 4340, and tool steel.
Stainless is the mixed group. Ferritic and martensitic grades such as 430, 420, and 440C are magnetic. Austenitic grades such as 304, 316, and 316L are near non-magnetic when annealed and become weakly magnetic after cold work.
6063 is made for extrusion and anodizing. It polishes and takes a clear anodize more evenly, but it is softer and lower in strength than 6061.
6061-T6 is the structural choice. It welds, machines cleanly, and holds threads. Use 6063 for trim, frames, and cosmetic parts; use 6061 when the part carries load.
Start from the load case. If the part is welded, hardcoated, or cost-sensitive, 6061-T6 is the answer at roughly 276 MPa yield.
If stiffness or strength drives the design and there is no weld, 7075-T6 gives roughly double the yield strength. Expect shorter tool life, more attention to chip evacuation, and a darker anodized finish.
Electroless nickel lays down an even 5–25 μm layer and covers inside corners and bores that a plating line cannot reach evenly. It is the safer call for complex geometry.
Chrome is harder and more wear-resistant on an exposed surface, but it builds on edges and needs a polishing step. For a shaft in a bushing, chrome. For a complex bracket, nickel.
Anodizing adds roughly half the coating thickness to each surface, so a 20 μm coating grows a feature by about 20 μm overall. Threads, dowel bores, and press fits are where this shows up first.
Tell us the finish before we cut. We can leave stock, mask the critical features, or hold the pre-finish dimension so the part still fits after coating.
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