AS 1897-1976

Specifies coating thickness, gauging after coating and other requirements for coatings on ISO metric triangular form threaded items specified in various Australian Standards. It covers tolerance classes 6H with G deviation, and 6G for nuts, and 6g, 6e and 8g for screws and bolts. Details of preplating thread dimensions for standard coating thicknesses and procedures for the modification and extent of modification to cater for thicker coatings are included. Surface areas of threaded items, statistical treatment for probability of acceptance by 'GO' gauge and recommended sampling procedures are dealt with in appendices.

This specification sets out requirements for electroplated coatings of cadmium, zinc, tin, nickel, nickel plus chromium, and copper plus nickel plus chromium, on steel or copper alloy items having threads of the ISO triangular form specified in the following Australian standards: AS 1110 ISO Metric Hexagon Precision Bolts and Screws AS 1111 ISO Metric Hexagon Commercial Bolts and Screws AS 1112 ISO Metric Hexagon Nuts, including Thin Nuts, Slotted Nuts and Castle Nuts AS 1275 Metric Screw Threads for Fasteners (Based on ISO Recommendations) AS 1721 General Purpose Metric Screw Threads.Section 2 details least pitches of standard metric threads which can accommodate standard coating thicknesses. Where standard fundamental deviations in pitches lower than those outlined in Section 2 are unable to accommodate the desired standard coating thickness, greater deviations are necessary and means for their determination are provided in Section 3.NOTES:1. The values specified with regard to the spread of plating thickness have been based on experimental work limited to fasteners coated by barrel plating.2. Orders to the requirements of this specification require supplementary information. Details of this information are set out in Appendix D.