Marking of Stainless Steel Fasteners

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The revised standard for the application for bolts, screws and studs with specified property classes (coarse thread and fine pitch thread) came into force on April 2009.

Marking of fasteners according to ISO 898.

Identification with the manufacturer’s mark and the property class is mandatory for:

  • Hexagon screws (4.6 to 12.9)
  • Hexagon or hexalobular socket head cap screws with thread diameter d ≥ 5 mm.

Marking of bolts and screws are preferably on the head. Where the shape of the screw always allows it.

Marking of studbolts.

For studbolts, marking is obligatory for property classes of or higher than 5.6 and it is preferably to be made on the threaded part by an indentation. For adjustment bolts with locking, the marking must be on the side of the nut.

Marking is required for:

  • bolts of nominal diameter
  • greater than 5 mm

The symbols shown in the table below are also authorized as a method of identification.

Marking of nuts. What are the difference between ISO and DIN?

Both for ISO and for DIN, property class is mandatory for hexagon nuts with thread diameter d ≥ 5 mm. Indeed, identification with the manufacturer is necessary mark, only for ISO standards.

Also, the hexagon nuts must be marked with an indentation on the bearing surface or:

  • on the side
  • by embossing on the chamfer.

Embossed markings must not protrude beyond the bearing surface of the nut.

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7 thoughts on “Marking of Stainless Steel Fasteners”

  1. Rachna Fasteners is an IATF 16949:2016 certified & CE Approved Fasteners manufacturer As Per EN-15048 Part-1 and 2 from TUV Nord leading manufacturer of high tensile hot and cold forged fasteners in India. EN 14399 manufacturer Supplier in India, Automotive fasteners, superior fasteners.

    1. Hi Carriage Bolt in India,this is the contact of our import/purchase department: Riccardo Borgognoni (

      Alessandro – Staff Inoxmare

  2. It’s interesting that embossed markings can’t protrude beyond the bearing surface of the nut, especially since there are so many kinds of them. I haven’t really been paying attention to the nuts, but I bet I’ll notice all kinds of markings on them once I do. Do all nuts have these kinds of lines and shapes?

    1. Hi Tori,
      in the latest version from 2012, the standard ISO 898 specifics the mechanical properties of fasteners made of carbon steel and alloy steel only. This is specified in the second part of ISO 898: “Nuts with specified property classes – Coarse thread and fine pitch thread”.

      This part of ISO 898 is applicable to nuts:

      a) Made of carbon steel or alloy steel
      b) With – Coarse thread M5 ≤ D ≤ M39, and fine pitch thread M8x1 ≤ D ≤ M39x3
      c) With triangular ISO metric thread according to ISO 68-1
      d) With diameter/pitch combinations according to ISO 68-1
      e) With specified property classes, including proof load
      f) With different nut styles: thin nuts, regular nuts and high nuts
      g) With minimum height m ≥ 0.45D
      h) With a minimum outside diameter or width across flats s ≥ 1,45D
      i) Able to mate with bolts, screws and studs with property classes according to ISO 898-1.

      For hot dip galvanized nuts, instead, you have to refer to ISO 10684.

      This part of ISO 898 does not specify requirements for properties such as:

      • prevailing torque properties (see ISO 2320);
      • torque/clamp force properties (see ISO 16047 for test method);
      • weldability;
      • corrosion resistance.

      Other details on the marking are contained in the full text of the standard.

      Alessandro – Staff Inox Mare

  3. All the things about is ie worth majoring are discussed over here. This article mentions and acts as such a moving trigger. It is an article worth applauding for based on its content. I love reading this blog; it talks so much about planning a great idea about it. Keep sharing such informative articles in future, will be appreciated. They offer same information here, one must check them also.

  4. This is a great informative piece on stainless steel fastener marking. I just wanted to add in.. Fasteners that do not fulfil the tensile or torsional requirements because of the geometry may be marked with the steel grade, but shall not be marked with the property class.

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