Stainless Steel 303

Your guide to 303 Stainless Steel Machining



The most readily machineable austenitic stainless steel

Ideal for moving parts

Not suitable for moist environments

303 is a highly machinable grade of stainless steel. Its non-seizing and non-galling properties make it ideal for moving parts.

This guide will take you through the main attributes, common applications, notes for designers and suitable finishing and treatments, as well as UK stock sizes and property tables. Don't forget to bookmark the page so you can refer back later.

If you are interested in 303 stainless machined parts, please scroll to the bottom of the page for more information about our service and to request a quote.

303 Guide: Properties, Applications and Design Considerations


What is 303 Stainless Steel?
Stainless steel 303 is the most readily machineable austenitic stainless steel.

The addition of Sulphur in the steel composition improves machining but also causes a decrease in the corrosive resistance and a slight reduction of the toughness when compared to 304.

303 Stainless Steel Machinability

Cutting edges should be kept sharp as dull edges cause excess work hardening.

Cuts should be light but deep enough to prevent work hardening by riding on the surface of the material.

You may also see 303 referred to as:

  • 1.4305 Bar
  • BS 303S31
  • EN 58M
  • AMS 5640
  • AMS QQ-S-764B Cond A
  • Australia – A S 2837-1986-303
  • Germany - W.Nr 1.4305 X10CrNiS 18 9
  • GB - BS970 Part3 1991 303S31, BS970 1955 EN58M
  • Japan - JIS G4303 SuS 303
  • USA - ASTM A582/582M-95b 303, SAE 30303 AISI 303, UNS S30300
  • S31

Industry Examples: Aerospace | Electrical | Architecture | Food & packaging


Typical Components & Applications: Shafts | Bushings | Gears | Food processing & production equipment | Valve bodies & fittings | Pump components | Nuts, bolts & screws | Aircraft fittings & parts | Springs

Main Attributes:
  • Excellent machinability
  • Non-seizing and non-galling properties make it ideal for moving parts
  • Good mechanical resistant properties 
  • Good corrosion resistance in mild environments (less corrosion resistance than 304)
  • Not suitable for moist/marine environments
  • Non-magnetic
  • Good resistance to oxidisation when intermittently exposed to temperatures of up to 760°C and continuous exposure to 870°C although not recommended for continuous use at 425-860°C as sensitive to carbide precipitation
  • Poor weldability

Finishing & Treatments:

303 stainless can’t be hardened by heat treatment. Solution treatment or annealing can be done by rapid cooling after heating to 1010-1120°C.

See our Finishing Processes page for further information on services that we can facilitate.

Can we meet your stainless steel 303 machining needs? Contact us now
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Further Reading & Resources

British Stainless Steel Association


303 Stainless Steel Machined Parts


Penta Precision provides the following 303 machining services: 
  • CNC milling
  • CNC turning
  • Prototypes and batch runs
  • Insert installation
  • Part marking
  • Manual milling
  • Manual turning
  • Machining design advice
  • Design for manufacture service

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