303 Stainless Steel
303 is a free-machining austenitic stainless steel with added sulphur, which makes it far easier to cut than 304 at the cost of some corrosion resistance and weldability.
- Family /
- Stainless Steels
- Machinability /
- ~78%
- Condition /
- Annealed
- Also called /
- three oh three
303 is a free-machining austenitic stainless steel with added sulphur, which makes it far easier to cut than 304 at the cost of some corrosion resistance and weldability.
Machinability is approximate and rated against free-machining 1212 steel at 100%. Higher is easier to cut.
What it is
Essentially 304 with sulphur added to break up chips. It is the grade chosen when a stainless part needs to be produced in quantity on a lathe and the service environment is not aggressive.
How it cuts
Much better behaved than 304 or 316 — chips break, finishes are good, and tool life is far more reasonable. Still not carbon steel, but a substantial improvement.
What catches people out
The sulphur that helps machining hurts both corrosion resistance and weldability. It is the wrong grade for marine or chemical service, and it should not be specified for parts that will be welded.
303 Stainless Steel — Common Questions
Can I substitute 303 for 304 to save money on machining?
- Only if the part is not welded and not in an aggressive environment. 303 machines far better, but its sulphur content reduces corrosion resistance and weldability. For marine or chemical service, that substitution will cause a failure.
Other stainless steels
Got a part for 303 Stainless Steel?
Send the drawing or the sample. We will tell you straight what it will take to make.