SAE、ASTM、IFI、ASME association standard and American National Standard draw up usa fasteners different mechanical and property grade, and made of fastener of regular part of low carbon steel, whole middle carob stell and alloy steel at the same time. Especially for the high strength bolt and nut, must impress under mark is strength grade and maker or seller. This is in"The Unit State Fastener act" regular that enter America market usa fasteners must have mark of the mark, and this is mandatory implementation. The mark including in fastener mechanical and property grade( or material and hot treatment) and maker mark. Property grade mark generally use maths, symbol or lettering, maker mark use symbol and lettering.
Property grade and maker mark lettering and code name use embossed sign of the head top of the bolt and screw, studs at the end of a side with gravure sign, Nut genera; in supporting the plane with the gravure sign. For the slotted and cross drive machine screw etc products, the standard regular do not make the mark sign. For the commodity usa fasteners that size equal or less than 1/4" or M5 because of the head so small that the standard regular do not mark sign.
For the buyer identification mark is best promise of the products quantity traceability. Only depend on unaided eye discerning mark of the strength especially and the adjust on usa fasteners applicability. Only depend on mark fastener maker discerning logo and will provide of buyer traceability.
When using find below quantity fastener, and according to mark held assemble from manufacturing and supplier and warn of the miniaturing and supplier must have responsibly of manufacturing or supply fit for the standard good products , mark have some binding of the manufacturing and supplier.
In the American Standard SAE J 429 "' outdoor usa fasteners machine and property and material requirement" the grade use maths mark from 1 to 8.2. The maths with strength grade have not quality correspond relation, but the maths bigger symbol of strength grade hinger, under the integer after decimal symbol strength grade same situation, only material or hot treatment style have some different. Head top mark style in the SAE standard use symbol.