Fastener Standards and Grade Classes
DIN, ANSI, BS, JIS, ASME, ASTM and IFI references, and what property class numbers actually mean.
Why one screw carries several standard references
A fastener standard covers dimensions, a material standard covers the steel, and a property class covers strength. A single screw can therefore reference a DIN number for its geometry, an ASTM grade for its material and a property class for its mechanical performance without any contradiction.
The dimensional standards
Deutsche Industrie Norm (DIN), American National Standards Institute (ANSI), British Standard (BS) and Japanese Industrial Standard (JIS) are the four geographic families still in everyday use, alongside ASME and the Industrial Fasteners Institute (IFI) references. Ehons produces to all of them.
Metric property classes
A class such as 8.8 encodes two numbers. The first is one hundredth of the nominal tensile strength in megapascals; the second is ten times the ratio of yield to tensile. So 8.8 means roughly 800 MPa tensile with yield at 80 per cent of it. The classes in common use here are 4.6, 4.8, 5.6, 8.8 and 10.9.
Imperial grades
SAE J429 Gr.2, Gr.5 and Gr.8 are the imperial equivalents in ascending strength. ASTM A307 Gr.A and Gr.B cover general bolting, with A394 and A449 covering specific structural applications.
Thread designations
Metric (M), Unified Coarse (UNC), Unified Fine (UNF) and British Standard Whitworth (BSW) are all produced. A screw and its mating thread have to share both the designation and a compatible tolerance class.
What to put on a purchase order
Dimensional standard or a drawing, material, grade or property class, thread designation, finish, and any inspection documents you need. A line that states all six cannot be misinterpreted; one that states two will be.
Put this into a quotation
Send the substrate, the thickness and the exposure and the right thread form, point and coating come back with the price.