Overview
ISO 7094:2000 specifies requirements for plain washers - extra large series - Product Grade C. The standard covers washers with nominal thread diameters from 5 mm to 36 mm and defines material hardness, general dimensions and acceptance criteria for washers intended primarily for use with metric fasteners in timber structures.
Key points from the standard include:
- Washers are of Grade C and made of steel with a nominal hardness of 100 HV (with an indicated hardness range up to 200 HV noted for related characteristics).
- Preferred and non-preferred dimensional series are provided (see Table 1 and Table 2 in the standard).
- The standard provides a model designation example: Rondelle ISO 7094-8-100 HV.
Key Topics
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Dimensions and series: ISO 7094 lists preferred and non-preferred dimensions for extra-large plain washers. These are organized by nominal thread diameter and include recommended passage hole, outer diameter and thickness ranges.
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Material and hardness: The document specifies steel washers with a hardness class of 100 HV, and references ISO 6507-1 for Vickers hardness testing methodology.
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Tolerances and quality: Tolerances for flat washers are covered by ISO 4759-3; surface quality requirements state that parts must be free of burrs and harmful defects.
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Surface finishes: Washers may be delivered unfinished, with protective lubricant, or with agreed coatings. Electrolytic coatings follow ISO 4042 and non-electrolytic zinc flake coatings follow ISO 10683.
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Acceptance and testing: Reception and inspection procedures are referenced to ISO 3269.
Applications
ISO 7094:2000 washers are intended for practical engineering uses where larger bearing surfaces are required, particularly:
- Structural timber assemblies using metric bolts and nuts.
- Connections where increased bearing area reduces local compression on wood substrates.
- Situations requiring standardized interchangeability with metric fasteners of Grade C and specified quality classes.
Benefits for engineers, specifiers and manufacturers:
- Compatibility with commonly used metric bolts and nuts for timber construction.
- Assured mechanical properties through defined hardness and referenced testing standards.
- Clear designation and ordering information reduces procurement errors.
Related Standards
- ISO 887 - Flat washers for general purpose (general plan)
- ISO 4759-3 - Tolerances for fasteners (flat washers)
- ISO 6507-1 - Vickers hardness test method
- ISO 3269 - Fastener acceptance inspection
- ISO 4042 and ISO 10683 - Surface treatment and coating specifications
For detailed dimensions, tables and figures, consult the full ISO 7094:2000 publication. The standard should be referenced alongside the related ISO documents listed above when specifying or testing extra-large plain washers for Grade C applications.
