Materials machined at Boyang Hardware
Boyang Hardware machines seven material families: aluminium (AL6061, AL6063, AL7075, AL2024, AL5052), stainless steel (SS303, SS304, SS316), brass (HPb59-1, CuZn39Pb1/2/3, CuZn40, C36000, C37710), bronze (C51000, C52100, C54400), carbon steel (Q235, 20#, 45#), titanium (Grade 2, Grade 5) and engineering plastics and composites (POM, PEEK, nylon, oiled nylon, carbon fibre). Tolerance capability varies by material and process and runs from 0.1 mm to 0.001 mm. A material certificate for the heat or lot used is supplied with every shipment.
Aluminium
Aluminium is the most frequently machined family here. It cuts fast, holds tolerance well, and takes anodising — which makes it the default choice for housings, brackets and enclosures where weight matters and corrosion resistance can be engineered with a finish rather than by choosing a more expensive alloy.
| Grade | Typical tensile strength | Machinability | Characteristics | Typical applications |
|---|---|---|---|---|
| AL6061 | ~310 MPa | Excellent | The general-purpose machined alloy. Good strength, excellent corrosion resistance, welds and anodises well, consistent supply | Housings, brackets, frames, jigs, heat sinks |
| AL6063 | ~186 MPa | Excellent | Softer and more formable than 6061; takes a very clean anodised surface, often used for extruded profiles | Enclosures, trim, architectural and cosmetic parts |
| AL7075 | ~572 MPa | Good | High strength, close to some steels, with good fatigue performance. Softer to machine than its strength suggests; anodises to a darker tone | Aerospace structures, high-stress brackets, moulds, racing components |
| AL2024 | ~469 MPa | Good | High strength with good fatigue resistance; lower corrosion resistance, usually protected by cladding or coating | Aircraft structures, high-load brackets |
| AL5052 | ~228 MPa | Very good | Best corrosion resistance of the common sheet alloys, excellent formability for bending and stamping | Marine parts, sheet metal enclosures, tanks, panels |
Stainless steel
Stainless steel is chosen for corrosion resistance rather than strength. It work-hardens under the cutter, so speeds, feeds and the choice of grade matter more than on aluminium: SS303 contains sulphur to break up chips and is markedly easier to machine, while SS304 and SS316 are tougher to cut but weld and perform better in service.
| Grade | Typical tensile strength | Machinability | Characteristics | Typical applications |
|---|---|---|---|---|
| SS303 | ~620 MPa | Excellent | Free-machining grade with sulphur added for chip breaking. Not suitable for welding. Slightly lower corrosion resistance | High-volume turned parts, fittings, nuts, bolts, connectors |
| SS304 | ~505 MPa | Moderate | The general-purpose austenitic grade. Weldable, formable, good corrosion resistance in most environments | Food-contact parts, medical hardware, general fittings, tanks |
| SS316 | ~580 MPa | Moderate | Molybdenum addition gives resistance to chlorides and marine environments. The go-to grade for salt water and aggressive chemistry | Marine hardware, chemical and pharmaceutical equipment, surgical instruments |
Brass and bronze
Copper alloys are the easiest families to machine and the most stable dimensionally after cutting. Brass is used where electrical conductivity, corrosion resistance and thread quality matter; bronze is used where the part is a bearing or a wear surface.
| Grade | Family | Typical tensile strength | Characteristics and applications |
|---|---|---|---|
| HPb59-1 | Brass | ~490 MPa | Lead-bearing free-cutting brass. Excellent machinability and thread quality; fittings, valve bodies, connectors |
| CuZn39Pb1/2/3 | Brass | ~400–480 MPa | European-designation leaded brass family, with the trailing digit indicating lead content. Hot formable and highly machinable; sanitary and plumbing fittings, turned components |
| CuZn40 | Brass | ~420 MPa | Higher zinc content; good hot working and reasonable machinability; general turned parts |
| C36000 | Brass | ~340 MPa | US-designation free-cutting brass. The reference grade for machinability; precision connectors, electrical contacts, small turned parts |
| C37710 | Brass | ~450 MPa | Forging brass with good strength and machinability; valve bodies and pressure fittings |
| C51000 | Phosphor bronze | ~340–450 MPa | Spring temper available; excellent fatigue and wear resistance; springs, electrical contacts, bearing cages |
| C52100 | Phosphor bronze | ~450–550 MPa | Higher tin content for greater strength and wear resistance; heavy-duty bearings and bushings |
| C54400 | Leaded phosphor bronze | ~350 MPa | Bearings, bushings and wear plates where machining ease and bearing performance both matter |
Carbon steel
| Grade | Type | Typical tensile strength | Characteristics and applications |
|---|---|---|---|
| Q235 | Structural mild steel | ~375–500 MPa | Weldable low-carbon structural steel, good toughness and low cost; brackets, frames, base plates, welded assemblies |
| 20# | Low-carbon steel | ~410 MPa | Chinese-designation low-carbon steel, similar in role to 1020. Machinable and case-hardenable; shafts, pins, general turned parts |
| 45# | Medium-carbon steel | ~600 MPa | Higher strength and hardness after heat treatment, with good machinability in the annealed condition; shafts, gears, spindles, stressed parts |
Titanium
Titanium is specified for strength-to-weight and corrosion resistance, and it is the material that punishes poor process control hardest. It conducts heat poorly, so heat concentrates at the cutting edge; it work-hardens, so a cutter that rubs instead of cutting will destroy the surface and the tool. Speeds are low, coolant delivery is critical, and tooling is consumed faster than on steel.
| Grade | Typical tensile strength | Characteristics and applications |
|---|---|---|
| Grade 2 (commercially pure) | ~345 MPa | Highly corrosion resistant and more machinable than the alloys. Chemical process equipment, medical implants, marine components |
| Grade 5 (Ti-6Al-4V) | ~950 MPa | The workhorse titanium alloy: high strength at low weight, good fatigue performance. Aerospace structures, medical instruments, high-performance components |
Engineering plastics and composites
| Material | Characteristics | Typical applications |
|---|---|---|
| POM (acetal) | High stiffness and low friction, dimensionally stable, machines cleanly | Gears, bearings, bushings, sliding components, insulators |
| PEEK | High temperature and chemical resistance, good mechanical strength, expensive | Semiconductor and medical components, high-temperature insulators, seals |
| Nylon | Tough and wear resistant; absorbs moisture, which changes dimensions over time | Wear pads, rollers, guides, light-duty gears |
| Oiled nylon | Nylon with oil compounded in for a self-lubricating surface | Bushings and bearings running without external lubrication |
| Carbon fibre | Very high stiffness-to-weight; requires diamond tooling and dust extraction | Lightweight structural panels, drone and aerial photography frames |
Achievable tolerance by material
| Material | CNC milling / turning | Grinding finish | Notes |
|---|---|---|---|
| Aluminium | ±0.01 mm | ±0.005 mm | Thermal expansion is significant on parts over ~200 mm: measure at a controlled temperature |
| Brass and bronze | ±0.01 mm | ±0.005 mm | The most dimensionally stable family; best tolerance consistency run to run |
| Stainless steel | ±0.01 mm | ±0.005 mm | Work hardening can shift a dimension on thin walls; sharp tooling is decisive |
| Carbon steel | ±0.01 mm | ±0.005 mm | Heat treatment after roughing introduces distortion; account for it in the process route |
| Titanium | ±0.02 mm | ±0.005 mm | Heat concentration and spring-back reduce achievable tolerance on slender features |
| POM, PEEK, nylon | ±0.02 mm | Not applicable | Cut in a stress-relieved state; nylon dimensions shift as moisture content changes |
| Carbon fibre | ±0.10 mm | Not applicable | Delamination risk at cut edges; tolerances set by the laminate, not the machine |
Surface finishes
| Finish | Aluminium | Steel | Stainless | Brass / bronze | Purpose |
|---|---|---|---|---|---|
| Anodising | Yes | No | No | No | Corrosion resistance, colour, light wear resistance |
| Hard anodising | Yes | No | No | No | Harder surface for sliding and wear faces |
| Sand blasting | Yes | Yes | Yes | Yes | Uniform matte texture |
| Polishing | Yes | Yes | Yes | Yes | Lower surface roughness, reflectivity |
| Annealing / heat treatment | Yes | Yes | Limited | Limited | Stress relief; hardness adjustment |
| Zinc plating | No | Yes | No | No | Sacrificial corrosion protection for steel |
| Chrome plating | Possible | Yes | Possible | Yes | Hardness, wear resistance, decorative finish |
| Powder coating | Yes | Yes | Yes | Limited | Durable coloured coating |
| Painting | Yes | Yes | Yes | Yes | Colour and light protection |
Finish certificates for outsourced processes such as plating and anodising are supplied with the shipment. More on inspection and documentation →
How to choose a material
In practice the material decision narrows quickly once four questions are answered.
- What is the environment? Salt water or chlorides rule in SS316 rather than SS304. Outdoors with a protective finish, anodised AL6061 is usually the cheapest correct answer.
- What is the load path? If the part carries structural load, compare AL7075 and 45# steel before assuming aluminium. AL7075 approaches mild steel in tensile strength at roughly a third of the density.
- Is the material on the drawing for a reason? If a grade was carried over from an older design, a machinability-led substitution can cut cost with no loss of function. AL6061 machines more predictably than AL7075 and is cheaper; SS303 machines far more easily than SS304 where welding is not required.
- Does the surface matter more than the substrate? Anodising colour and texture depend on alloy and temper, so a cosmetic part should be specified by finish requirement, not by grade alone.
What is supplied with the material
- Material certificate for the heat or lot actually used, stating chemistry and mechanical values.
- Traceability from the certificate to the parts produced from that material.
- Finish certificates for outsourced plating or anodising.
- If a specific mill, country of origin or standard is required, state it at quotation — availability is confirmed before the order is accepted rather than after.
Questions about materials
Which aluminium grade is best for CNC machined parts?
AL6061 for most parts: it has good strength, excellent corrosion resistance, machines predictably and anodises well. AL7075 is specified when strength is the binding constraint and cost is secondary. AL5052 is used for sheet components that need to be formed. See process comparison for how the choice interacts with the manufacturing method.
SS304 or SS316 — which should I specify?
SS316 contains molybdenum, which gives it resistance to chlorides and marine environments; SS304 does not. If the part will see salt water, de-icing salts or chloride-bearing process chemistry, specify SS316. For indoor, freshwater or general industrial use, SS304 is sufficient and less expensive.
Can you supply material certificates?
Yes. A material certificate for the heat or lot used is supplied with the shipment as standard, along with the dimensional inspection report. If a specific standard, mill or country of origin is required, state it at quotation so it can be confirmed before the order is accepted.
Do you machine titanium on a production basis?
Yes, Grade 2 and Grade 5 (Ti-6Al-4V). Titanium requires lower cutting speeds, rigid set-ups and generous coolant delivery, and tooling is consumed faster than on steel, so it is quoted as its own process route rather than as an aluminium part in a different material.
Can you work from a material I supply?
In some cases. Customer-supplied material is quoted individually and requires that dimensions, grade and certification are documented on receipt, because the machine shop cannot otherwise certify the final part. Send the material specification and quantity and it will be confirmed.
Send us the drawing
Material recommendation, achievable tolerance and lead time are confirmed in the quotation, normally within 1–2 working days.