Stainless 420 Guide | Machining Design Considerations | Penta Precision       +44 (0) 2392 668 334

Stainless Steel 420 Machined Parts

A Guide to 420 CNC Milled & Turned Parts

What is stainless 420?

Stainless 420 is a general purpose high carbon martensitic steel. It is usually supplied hardened and tempered or annealed condition. Martensitic stainless steels are designed for high hardness and sometimes other properties are compromised on. 

420 has the highest hardness amongst all stainless grades with 12% chromium. The addition of sulphur to improve machinability does lower the corrosion resistance and weldability to below that of grade 410 (non-free machining equivalent).

Main Attributes of 420:

  • Rust resistant
  • High hardness
  • Exceptional wear resistance
  • Good corrosion resistance achieved when hardened and surface ground or polished (to atmosphere, foods, fresh waters, mild acids)
  • Magnetic
  • Although it can be used in continuous service up to 650°C, this can result in a considerable drop in its core properties (hardness, tensile strength, corrosion resistance), therefore not recommended for use at working temperatures above 400°C


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Stainless 420 Machining Characteristics

Stainless 420 machines best in the hardened and tempered condition R or condition S. It is similar to machining high carbon tool steels in that it gives tough, stringy chips. There is a free-machining type of 420 but this does come at the expense of other properties.

Finishing & Treatments

Stainless 420 is usually supplied in a heat treated condition:

Similar or obsolete designation and trade names

You may also see stainless 420 referred to as:

420 Components, Applications & Industries

Here are some examples of the industries and components for which stainless 420 is appropriate. This is by no means an exhaustive list. Please do get in touch if you are considering using 420 and we can talk through your project with you.

Typical Components & Applications:
  • Surgical and dental instruments
  • Cutting tools
  • Wear plates
  • Needle valves
  • Hand tools
  • Bushings
  • Pump parts
  • Valve parts
  • Shafts
Industry Examples:
  • Medical
  • Food processing

    420 Machining Service

    Penta Precision provides highly accurate machined parts in 420. Customers turn to us when they have had quality and delivery issues with their existing suppliers and need a reliable precision machining partner.

    Penta Precision provides the following +17/4PH services: 

    • CNC milling – prototypes & large batch runs
    • CNC turning – prototypes & large batch runs
    • Insert installation
    • Part marking
    • Manual milling
    • Manual turning
    • Machining design advice
    • Machining drawing service

    Reasons to Choose Penta:

    • ISO 9001:2015 quality assurance
    • Consistent high quality machined parts
    • Reliable delivery dates - our track record speaks volumes
    • Exceptional customer service and communication
    • Machining design advice
    • Extensive experience in our field
    What Makes Penta Different?

    Our 3 unique pillars to delivering exemplary service:

    • We Communicate well 
    • We take Care at each stage
    • Our service is Consistent

    See our ‘Proven Process’ page to find out more

    We are regularly machining 420 for customers all over the UK. Our customers depend on our machining expertise as well as our outstanding delivery performance, to machine the highest quality parts. If you'd like to discuss how we can help you with your 420 machining requirements, here's a list of ways to get in touch with us.

    Can we meet your
    stainless 420 machining needs?
    Call our engineering team on
    +44 (0) 23 9266 8334
    or contact us via our email form

    “Penta provide an excellent service to us. They offer a helpful, professional and friendly service. I would recommend anyone looking for sub-contracting machining use them '' Peter - Business Development Manager 

    Tel: +44 (0) 2392 668 334

    Fax: +44 (0) 2392 668 335

    Connect with us:

    Penta Precision Engineering Ltd

    Aspen House

    Airport Service Road



    PO3 5RA

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