Flange bolts can be divided into metric system and inch system. The common metric system standard is DIN6921, have serrated type and non-serrated type .It is used together with DIN6923 hex flange nuts. The common grades are 4.8/8.8/10.9/12.9, oxidation black surface treatment, galvanized surface treatment, hot galvanized surface treatment, Dacromet, Teflon, etc.
The common standard of the British system is ASME B 18.2.1. The grade is 2/5/8. There are two thread types, UNC and UNF, which can be used together with American flange nuts.
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