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Metric High Strength Structural Bolts
April 4, 2003
Gerald E. Schroeder, P.E.Metric structural fastener assembly components are produced under the following ASTM specifications: A325M and A490M for bolts, A563M for nuts, F436M for washers and F959M for direct tension indicators.
The specifications listed above specify available nominal fastener sizes that can be produced. State metric fastener specifications should comply with these ASTM standards.
Metric projects typically have all documents, including the fastener specifications, referencing only metric standards. Many States allow the substitution of inch series fasteners for the metric fasteners on metric projects. Typically, when this is done, there are no specifications in the contract documents covering inch series fasteners. It is my opinion that the inch series specifications should be included in the contracts if the substitution is allowed.
