Free-Machining Stainless

303 Stainless Steel CNC Machining

The most machinable austenitic stainless steel. Excellent for high-volume production with superior surface finishes and minimal tool wear.

View Properties

Specifications

Designation:UNS S30300 / AISI 303
Type:Austenitic (Free-Machining)
Composition:18% Cr, 8% Ni, 0.15% S
Machinability:78% (vs 100% for brass)
Australian Std:AS 2837 Grade 303

Why Choose 303 Stainless?

Best Machining in Stainless

Sulfur addition creates excellent chip breaking and reduces tool wear. 60% faster than 304 stainless with better finishes.

Good Corrosion Resistance

Comparable to 304 in most environments. Suitable for atmospheric, freshwater, and mild chemical exposure.

Cost Effective

Lower machining costs from reduced cycle times and extended tool life. Ideal for high-volume precision components.

Excellent Finish

Superior surface finish capability. Minimal secondary finishing required for most applications.

Technical Properties

Chemical Composition (%)

Chromium (Cr)17.0 - 19.0
Nickel (Ni)8.0 - 10.0
Sulfur (S)≥ 0.15 (free-machining)
Manganese (Mn)≤ 2.0
Carbon (C)≤ 0.15
Note: High sulfur content improves machinability but reduces weldability and corrosion resistance vs 304.

Mechanical Properties

Tensile Strength515-655 MPa
Yield Strength240-310 MPa
Elongation40-50%
Hardness≤ 217 HB
Machinability Rating78% (excellent)

Applications

Precision Components

  • • Fasteners and screws
  • • Shafts and pins
  • • Fittings and couplings
  • • Instrument parts

Aerospace

  • • Aircraft fittings
  • • Bushings
  • • Valve bodies
  • • Hydraulic fittings

Industrial

  • • Gears and bushings
  • • Pump shafts
  • • Valve components
  • • Textile machinery parts

Not Recommended For

Marine environments, welded structures, or applications requiring 304-level corrosion resistance. Not suitable for food contact due to sulfur content.

CNC Machining 303 Stainless

Machining Rating: Excellent (Best in Stainless)

Significantly better machinability than 304. Ideal for automatic screw machines and high-volume CNC production.

Machining Parameters

Turning (Carbide)90-140 m/min
Milling (Carbide)80-120 m/min
Drilling30-50 m/min

Best Practices

  • ✓ Higher speeds than 304 (60% faster)
  • ✓ Excellent chip breaking characteristics
  • ✓ Coolant recommended for best results
  • ✓ Sharp tools for superior finish
  • ✓ Ideal for automatic screw machines

High-Speed 303 Stainless Machining

Fast production cycles for precision components with excellent surface finishes.