303 Stainless Steel (UNS S30300) is a good-to-machine material that we run regularly for export customers. It has a density of 7.92 g/cm3, a tensile strength of 620 MPa and a typical hardness of HB 200. Those numbers make it the right choice for shafts and fittings, and a poor choice when cost or corrosion resistance matters more than mechanical performance.
On our machines we hold +/-0.01 mm on turned and milled features and reach Ra 0.8 um where the drawing calls for it. Standard lead time for 303 Stainless Steel parts is 3-7 working days, including material procurement, machining and any finishing operation you specify.
303 Stainless Steel: key properties
| Property | Value |
|---|---|
| UNS / designation | S30300 |
| Density | 7.92 g/cm3 |
| Tensile strength | 620 MPa |
| Hardness | HB 200 |
| Machinability | Good |
| Suggested cutting speed (carbide) | 150-200 m/min |
| Relative material cost | 3 of 5 |
Machining 303 Stainless Steel: what to plan for
- Not for welding
- Slightly lower corrosion resistance than 304
- Sulfur inclusion
Cutting speed for 303 Stainless Steel with carbide tooling sits around 150-200 m/min. Going faster burns the edge; going much slower causes rubbing and a poor surface. Air blast or flood coolant both work, but chip evacuation must be positive. If your part has thin walls or a lot of stock to remove, say so in the RFQ — we plan roughing, stress relief and finishing as separate operations when the geometry demands it.
Parts we machine in 303 Stainless Steel
- Shafts
- Fittings
- Nuts and bushings
- Screw-machine parts
Most 303 Stainless Steel work arrives as 2D drawings with a mix of critical and non-critical features. Loosening tolerance on the non-critical ones is the fastest way to cut cost, and we will tell you which features those are before we quote.
Tolerances, finish and lead time
| Item | Capability |
|---|---|
| General tolerance | +/-0.01 mm |
| Achievable surface finish | Ra 0.8 um |
| Minimum wall thickness | 0.8 mm (aluminium) / 1.0 mm (steel and stainless) |
| Typical lead time | 3-7 working days |
| Prototype quantity | 1 piece |
| Production quantity | 10 to 50,000 pieces |
Frequently asked questions
What is the lead time for 303 Stainless Steel parts?
Standard is 3-7 working days from drawing release, assuming the material is in stock. Exotic grades and cast forms can add 5 to 10 days. Finishing such as anodizing or plating adds 3 to 5 days.
What tolerance can you hold in 303 Stainless Steel?
+/-0.01 mm is routine on turned and milled features. Tighter than that is possible on specific features by grinding or lapping, but it is quoted separately because it changes the process.
Do you keep 303 Stainless Steel in stock?
We hold common sizes of 303 Stainless Steel and buy mill-certified stock for everything else. Material certificates are supplied with the parts on request.
Can you supply 303 Stainless Steel parts with a certificate of conformity?
Yes. We issue a dimensional report, a material certificate and a certificate of conformity as standard for production orders, and full PPAP or AS9102 paperwork when the programme requires it.
Related pages
- Materials — the full index for this section.
- 304 Stainless Steel CNC Machining: Cost and Tolerances
- 316L Stainless Steel CNC Machining for Marine and Medical
- MIC-6 Cast Aluminum Tooling Plate Machining
- 17-4 PH Stainless Steel CNC Machining After H900 Aging
- Instant CNC quote
- Tolerance quick reference
- Frequently asked questions
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