GMW25

Description / Abstract: GMW25, 5th Edition, July 2020 - Mechanical Properties and Material Requirements for Externally Threaded Fasteners

This specification defines the mechanical and material requirements for externally threaded fasteners sized M39 and smaller. This specification is based on ISO 898-1. However, only Property Class described in this document shall be used.

Note: Nothing in this standard supercedes applicable laws and regulations.

Note: In the event of conflict between the English and domestic language, the English language shall take precedence.

Purpose/Material Description.

The fasteners applicable to this specification are formed from steel wire or bar and heat treated by quench and tempering, as required by the property class. The chemical composition, internal cleanliness of the steel, mechanical properties, microstructure, and other physical properties are described in this document.

Symbols.

Not applicable.

Applicability.

This specification applies to bolts, screws, SEMS (bolts with washer assembly), threaded plugs, and studs.

This specification may be referenced partly for non-standard grades such as work-hardened and bainitic/austempered grades. See Appendix B for guidance.

Remarks.

GM does not allow new release of fasteners with property class 9.8. The properties listed are for reference for legacy parts only.

Externally threaded fasteners with strength property class 10.9, including proposed austempered types with hardness 39 HRc (Rockwell Hardness) (385 HV (Vickers Hardness)), shall not be used for any application that may be exposed to environmental chlorides (such as road salt), regardless of fastener coating. Fasteners property class 10.9 shall be released only after approval from GM Fastener and Materials Engineers.

Special “underlined grades” (identified as 12.9 for example) per ISO 898-1 are not permitted.

The scope of ISO 898-1 does not include threaded plugs. For the purpose of this specification, a threaded plug can be considered a very short bolt.