303 Stainless Steel Fittings – The World’s No.1 Free-Machining Grade for High-Volume CNC Production
When your automatic screw machine or CNC lathe needs to run faster, 303 Stainless Steel Fittings deliver the competitive edge. With 0.15–0.35 % sulfur deliberately added, this austenitic grade offers 2–3× higher machining speeds and superior chip-breaking compared to standard 304 or 316, while still providing good corrosion resistance for mild-service applications. From bright-bar hex nipples and hose barbs to precision-turned instrumentation elbows, 303 Stainless Steel Fittings maximise spindle uptime, extend tool life, and reduce unit cost—making them the first choice for high-volume producers of pneumatic, hydraulic, and food-processing components worldwide.
303 Stainless Steel Fittings – Ultra-Machinable Threaded & Turned Components for High-Volume Production
Key Features & Benefits
- Free-machining sulfur 0.15–0.35 % – 90 % machinability rating vs 45 % for 304
- Excellent chip break-up – longer tool life, lower production cost
- Good corrosion resistance for indoor, food-zone, and mild chemical environments
- Non-galling / non-seizing – ideal for moving screw-machine parts
- Non-magnetic in annealed condition; low permeability after cold work
- Available in both standard and precision-machined specials
- Full ASTM A582, ASME B16.11, EN 1.4305 compliance
- 100 % recyclable, RoHS compliant
Technical Specifications
Table 1 – Chemical Composition (ASTM A582)
| Element | 303 % | 303Se % | 304 % |
|---|---|---|---|
| Cr | 17.0–19.0 | 17.0–19.0 | 18.0–20.0 |
| Ni | 8.0–10.0 | 8.0–10.0 | 8.0–10.5 |
| S | 0.15–0.35 | ≤0.060 | ≤0.030 |
| Se | — | ≥0.15 | — |
| C | ≤0.15 | ≤0.15 | ≤0.08 |
| Fe | Balance | Balance | Balance |
Table 2 – Mechanical & Machinability Data
| Property | 303 Fittings | 304 Fittings | 316 Fittings |
|---|---|---|---|
| Tensile Strength | ≥620 MPa | ≥515 MPa | ≥515 MPa |
| Yield Strength (0.2 %) | ≥310 MPa | ≥205 MPa | ≥205 MPa |
| Elongation in 2" | ≥35 % | ≥40 % | ≥40 % |
| Hardness HRB | 90–100 | ≤92 | ≤95 |
| Machinability Rating | 90 % (excellent) | 45 % (good) | 45 % (good) |
| Chip Break-Up | Superior | Fair | Fair |
| Weldability | Poor* | Excellent | Excellent |
*Welding not recommended due to hot-cracking risk; use 304/347 for welded joints and bolt on 303 parts.
Full Product Range Table
| Fitting Type | Size Range | Pressure Class | Standards | Finish |
|---|---|---|---|---|
| 303 stainless steel fittings – threaded (NPT, BSPT, BSPP) | ⅛"–4" | 150 lb / 3000 lb / 6000 lb | ASME B16.11, ISO 7-1 | Pickled, bright |
| Socket-weld forged | ¼"–4" | 3000 lb / 6000 lb | ASME B16.11 | Pickled |
| Hose barbs & hose fittings | ⅛"–2" | 250 psi | Custom | Bright |
| Compression & instrumentation | ⅛"–2" | 10 000 psi | DIN 2353, ISO 8434-1 | Bright annealed |
| Turned hex nipples, bushings, plugs | ⅛"–2" | Custom | ASTM A582 | Bright |
| Elbows, tees, crosses, couplings | ⅛"–4" | Custom | ASTM A582 | Bright |
| Custom CNC machined specials | 5–200 mm | Custom | ASTM A314 | Mirror Ra ≤0.4 µm |
Special selenium-grade 303 stainless steel fittings available on request.
Main Applications
- Automatic lathe & CNC mass production of precision components
- Pneumatic & hydraulic systems – quick-connect nipples, adapters
- Instrumentation – compression fittings, sensor housings
- Valve parts, pump trim, compressor components
- Food-processing equipment parts requiring extensive machining
- Automotive fasteners, electronic connectors, terminal blocks
- 303 stainless steel fittings for low-pressure dairy lines
2–3× Faster Machining – 303 Stainless Steel Fittings Ideal for Automatic Screw Machines & CNC Shops
Why Choose Us – Machining-Grade Specialist
- ISO 9001 & PED certified mill – EN 10204 3.1 & 3.2 MTC supplied
- 150 000 tons annual machining-grade stainless capacity – 5-day lead time
- In-house threading & turning lines – NPT, BSPP, BSPT, metric, UNF
- Same-day shipping for standard 303 stainless steel fittings – 30 000 t ready stock
- Custom CNC specials within 7 days – tolerances ±0.05 mm
- Global export to 70+ countries – fumigation-free crates, vessel booking, insurance
Massive Ready Stock of 303 Stainless Steel Fittings – Mill-Direct Prices, Ships Today Worldwide
Grade Comparison Table: 303 vs 303Se vs 304 vs 316 vs 416 vs 430F Fittings
| Grade/Type | S/Se % | Mo % | Machinability | Weldability | Magnetic | Relative Cost | Best Use |
|---|---|---|---|---|---|---|---|
| 303 | S 0.15–0.35 | 0 | 90 % | Poor | No* | 1.0× (base) | High-speed machining |
| 303Se | Se ≥0.15 | 0 | 95 % | Poor | No* | 1.1× | Ultra-smooth finish |
| 304 | ≤0.030 | 0 | 45 % | Excellent | No* | 0.95× | General corrosion |
| 316 | ≤0.030 | 2–3 | 45 % | Excellent | No* | 1.35× | Marine chloride |
| 416 | S ≥0.15 | 0 | 95 % | Poor | Yes | 0.9× | Magnetic fasteners |
| 430F | S ≥0.15 | 0 | 90 % | Poor | Yes | 0.8× | Non-corrosive shafts |
*Non-magnetic in annealed condition; slight magnetism possible after cold work.
FAQ – 303 Stainless Steel Fittings
-
What is the machinability rating of 303 stainless steel fittings?
90 % (excellent) vs 45 % for 304; chip break-up is superior, tool life 2–3× longer. -
Can 303 stainless steel fittings be welded?
Welding is not recommended due to hot-cracking risk; use 304/347 for welded joints and bolt on 303 parts. -
Difference between 303 and 303Se fittings?
303Se contains ≥0.15 % selenium instead of sulfur, providing even better chip breaking and smoother surface finish. -
What is current stock status for 303 stainless steel fittings?
30 000 t ready stock; live portal updated every 30 minutes. -
What is the minimum order quantity?
One carton for stock items; full container (≈20 t) for custom CNC specials. -
Lead time for custom CNC parts?
7 days for specials; 24 h for standard 303 stainless steel fittings. -
Which certificates accompany the shipment?
EN 10204 3.1/3.2 MTC, ISO 9001, PED 2014/68/EU, and third-party inspection (SGS/TÜV/BV). -
Which countries receive your exports?
More than 70 countries including USA, Germany, India, Brazil, UAE, South Korea, and Australia.
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