What materials are self-drilling and self-tapping fasteners made from?

Self-drilling fasteners are manufactured from several different grades of steel, and it’s essential to use the correct grade in the correct environment. The common grades of steel used for the manufacture of self-drilling fasteners include:

• Carbon steel

• Martensitic stainless steel

• Austenitic stainless steel

• Super austenitic stainless steel (usually used for self-tapping fasteners)

What are the differences between self-drilling fastener materials?

Carbon steel is the lowest grade of steel used for self-drilling fasteners and is most vulnerable to corrosion. Typical grades used would include SAE1022. Fasteners manufactured from carbon steel should always have a corrosion-resistant coating.

Martensitic stainless steels have a high carbon steel content, so are still susceptible to corrosion. Typical grades used for fasteners include AISI 410.

The majority of stainless-steel fasteners are made from Austenitic stainless steel which offers excellent corrosion resistance. This is an alloy featuring a certain percentage of chromium and nickel. The most common grades are A2/304 and A4/316. The difference is that A4/316 contains Molybdenum which is added for enhanced corrosion resistance.

Super Austenitic stainless steels (HCR – High Corrosion Resistance) have increased levels of chromium, nickel and molybdenum to give even greater resistance to corrosion. Typical grades include EN1.4547 and EN1.4529 which are not susceptible to chloride-induced stress corrosion cracking.

Why are self-drilling fasteners made from different materials?

The material used will depend on the durability required and the environment that the self-drilling fastener will be used in. Using the wrong material can lead to corrosion and cause the fastener to fail.