ISO standard: Nut performance will change

Mechanical properties of ISO / FDIS 898-2 carbon steel and alloy steel fasteners – Part 2 Nuts special performance grade – coarse and fine thread.

According to John Newnham, a fastener specialist at the British Forging Association's Confederation of British Metalforming, the International Organization for Standardization (ISO) has released the final draft of the latest ISO 898-2, which has been approved by the BSI Fasteners Standards Committee FME/9. This standard is the basic mechanical performance standard for metric threaded nuts and has some significant changes compared to previous versions.

The most obvious change is that it replaces the two existing standards. BS EN 20898-2:1994, ISO 898-2:1992 with coarse metric threaded nuts and BS EN ISO 898-6:1996 for metric fine nuts are updated to the same version. This change will be very popular because it only needs to meet one standard! This document will be applicable to ISO metric threaded nuts. The specifications range from coarse thread diameters from M5 to M39 and fine thread diameters from M8 to M39.

The new standard has completely revised existing standards and there are several technical changes. For thin nut standards (D refers to nominal diameter) with a height of 0.45D to 0.8D - Style 0, has been adopted with the existing style 1 for ordinary nuts and style 2 for high nuts. The nominal diameter range applied to the nut type and performance class has been partially changed, and the guidelines for existing nut designs and the performance levels of ISO metric bolts have been further added and clarified.

The substance composition table for each grade and type has been added, including changes in the minimum amount of manganese, and the maximum amount of phosphorus and sulfur in some grades. In addition, it is easier to understand that the mechanical performance table has been reorganized. The current hardness table includes Brinell and Rockwell values ​​instead of using the existing Vickers hardness value conversion standard. The mechanical performance test method has been partially revised and added, and now includes some previously undocumented test tool sizes and hardnesses.

It seems logical to be wise to modify the existing two standards, but manufacturers will need to ensure that their products meet the chemical composition adjustments and modifications to the mechanical testing requirements. Products in stock may also not fully meet the changing standards. However, the basic performance requirements of the nut have not been modified. Therefore, if the previous mechanical test is the correct test method, the manufacturer should have some confidence that the inventory product that meets the previous standard mechanical characteristics will also conform to the new standard. A major concern in the near future is that any customer or country that adheres to the latest ISO standard specifications will choose to phase out previously manufactured parts after the new standard is released. This happens because ISO does not specify any reference standard date policy in the manufacturer's product drawings, so the new standard will soon be adopted.

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