Technical Guide
9 min read
Material Grades for Precision Machining: A Buyer's Reference
Grade-level reference for brass, stainless steel, mild steel, carbon steel, copper, aluminium, and gunmetal alloys used in precision CNC machining. Includes applications by industry and key selection factors.
Selecting the right material grade at the drawing stage avoids costly substitutions, failed inspections, and compliance issues. Different industries require specific alloys based on machinability, corrosion resistance, strength, conductivity, and regulatory compliance. The grades below reflect what Pixon Metals routinely machines and supplies.
Brass Grades
| Grade | Designation | Key Property | Typical Applications |
|---|---|---|---|
| Free Cutting Brass | CZ121 / CW614N / IS 319 | Highest machinability; 3% Pb chip-breaker | Electrical connectors, fasteners, fittings — high-volume CNC turning |
| Corrosion-Resistant Brass | CZ131 / CW606N | Better corrosion resistance than CZ121 | Marine-adjacent, humid environments, general engineering |
| DZR Brass | CZ132 / CW602N | Arsenic-treated; resists dezincification | Hot water plumbing, valves, compression fittings |
| Free Machining Brass (USA) | C36000 | ASTM equivalent of CW614N; 3% Pb | US-market components, screw machine parts |
| Forging Brass | C37700 | High zinc; excellent hot forgeability | Forged valve bodies, hydraulic fittings, automotive parts |
| Cartridge Brass | C28000 | 70% Cu / 30% Zn; excellent cold forming | Deep-drawn shells, radiator cores, ammunition cases |
For CNC turning in India, IS 319 (equivalent to CW614N / CZ121) is the default. Specify your exact grade if your application requires DZR, lead-free, or a specific international designation.
Stainless Steel Grades
| Grade | Type | Key Property | Typical Applications |
|---|---|---|---|
| SS 304 / 304L | Austenitic | General-purpose; good corrosion resistance; widely available | Food equipment, enclosures, fasteners, structural parts |
| SS 316 / 316L | Austenitic (Marine) | Molybdenum addition; superior chloride resistance | Marine, medical implants, chemical processing, offshore |
| SS 303 | Austenitic (Free-Machining) | Sulphur addition improves machinability | CNC turned parts, shafts, fittings requiring good finish |
| SS 410 | Martensitic | Hardenable; moderate corrosion resistance | Valves, pump shafts, fasteners, cutlery |
| SS 420 | Martensitic | Higher carbon; high hardness when heat-treated | Surgical instruments, gauge parts, tooling components |
| Duplex 2205 | Duplex (Austenitic-Ferritic) | High strength + high corrosion resistance | Oil & gas, chemical plant, pressure vessels |
| 17-4 PH | Precipitation Hardening | Very high strength; good corrosion resistance | Aerospace, defence, high-performance fasteners |
Mild Steel (Low Carbon) Grades
| Grade | Standard | Key Property | Typical Applications |
|---|---|---|---|
| IS 2062 | BIS (India) | General structural steel; weldable | Construction, structural fabrication, brackets |
| ASTM A36 | ASTM (USA) | Low carbon; good weldability and formability | Structural shapes, plates, flanges |
| EN8 / 080M40 | BS (UK) / EN 10083 | Medium carbon; good strength and toughness | Automotive shafts, keys, general machined parts |
| EN1A / 230M07 | BS (UK) | Free-cutting; sulphur addition | High-volume turned parts, bolts, screws, studs |
| SAE 1018 / 1020 | SAE (USA) | Low carbon; easily welded and machined | Shafts, pins, bushes, general engineering parts |
Carbon Steel (Medium and High) Grades
| Grade | Standard | Key Property | Typical Applications |
|---|---|---|---|
| EN8 / C45 | BS / DIN 17200 | Medium carbon; hardenable; good fatigue resistance | Automotive components, shafts, keys, couplings |
| EN9 / C55 | BS / DIN 17200 | Higher carbon; higher strength and hardness | Heavily loaded parts, springs, clutch discs |
| EN19 / 40CrMoV | BS alloy steel | Alloy steel; high strength after heat treatment | Gears, crankshafts, heavy-duty fasteners, oil & gas parts |
| SAE 1045 / 1055 | SAE (USA) | Medium-high carbon; good wear resistance | Fasteners, axles, sprockets, precision forgings |
| ASTM A216 WCB | ASTM (Casting) | Carbon steel casting grade; pressure-rated | Valves, pump casings, pressure-rated bodies |
Copper Grades
| Grade | Designation | Key Property | Typical Applications |
|---|---|---|---|
| Oxygen-Free Copper | C10100 (OFE) | Highest purity (99.99% Cu); lowest oxygen | High-frequency electrical, vacuum equipment, scientific instruments |
| Electrolytic Tough Pitch (ETP) | C11000 | 99.9% Cu; standard electrical copper | Busbars, lugs, earthing hardware, general electrical |
| Phosphorus Deoxidized | C12200 (PDC) | 0.015–0.040% P; excellent for welding and brazing | HVAC tubing, refrigeration lines, plumbing, heat exchangers |
Aluminium Grades
| Grade | Temper | Key Property | Typical Applications |
|---|---|---|---|
| 6061 / 6061-T6 | T6 (heat treated) | Excellent machinability; good strength and corrosion resistance | Structural parts, automotive, general machined components |
| 6082 | T6 | Higher strength than 6061; good weldability | Structural engineering, heavy-duty turned parts |
| 7075 | T6 / T73 | Very high strength; aerospace-grade | Aerospace structures, high-stress components, tooling |
| 2024 | T3 / T4 | High fatigue resistance; good machinability | Aircraft fuselage, wing skins, high-load structural parts |
| 5052 | H32 / H34 | Excellent corrosion resistance; non-heat-treatable | Marine, fuel tanks, pressure vessels, sheet metal work |
Gunmetal and Bronze Grades
| Grade | Designation | Composition (approx.) | Typical Applications |
|---|---|---|---|
| Gunmetal | LG2 / CuSn5ZnPb5 | 85% Cu, 5% Sn, 5% Pb, 5% Zn | Marine valves, pump bodies, bearings, pressure fittings |
| Bearing Bronze | C93200 / SAE 660 | 83% Cu, 7% Sn, 7% Pb, 3% Zn | Bushings, plain bearings, sleeve bearings |
| Phosphor Bronze | PB1 / C51000 | 94% Cu, 5% Sn, 0.2% P | Springs, electrical contacts, bearings, diaphragms |
| Aluminium Bronze | AB2 / C95400 | 91% Cu, 4% Fe, 4% Al, 1% Mn | Marine hardware, gears, wear plates, high-load bearings |
Key Material Selection Factors
- Environment — temperature, moisture, chemical exposure, and pressure rating
- Machinability — free-machining grades (IS 319, EN1A, SS 303) lower production cost
- Compliance — RoHS (lead restriction), NSF 61 (drinking water), AMS (aerospace)
- Tolerances and finish — harder materials hold tighter tolerances but cost more to machine
- Standards reference — specify grade and standard on drawing (e.g., IS 319, CW614N, SS 316L per ASTM A276)
Frequently Asked Questions
What is the difference between SS 304 and SS 316?
SS 304 is the standard austenitic grade — good corrosion resistance in most environments. SS 316 adds molybdenum (2–3%), which significantly improves resistance to chlorides and marine environments. Specify 316 or 316L for marine, medical, or chemical applications; 304 is adequate for most general-purpose uses.
When should I specify free-machining grades?
Specify free-machining grades (IS 319 brass, EN1A steel, SS 303) when you need high production volume, fine surface finish, or tight thread tolerances at competitive cost. Avoid them where the sulphur or lead content may cause issues — for example, SS 303 is not recommended for welding or for applications with strict corrosion requirements in chloride environments.
Can Pixon Metals machine all these grades?
Yes. Brass (IS 319, CW614N, DZR, lead-free), stainless steel (304, 316, 303), mild and carbon steel (EN8, EN1A, IS 2062), copper (C11000, C12200), aluminium (6061, 6082), and gunmetal (LG2) are all standard materials on our shop floor. Specify the grade and applicable standard on your drawing.