Fastener Material Selection

Fastener Material Selection

There is no one fastener material that is right for every environment. Selecting the right fastener material

from the vast array of materials available can appear to be a daunting task. Careful consideration may need

to be given to strength, temperature, corrosion, vibration, fatigue and many other variables. However, with some basic knowledge and understanding, a well thought out evaluation can be made.

Mechanical Properties

Most fastener applications are designed to support or transmit some form of externally applied load. If the strength of the fastener is the only concern, there is usually no need to look beyond carbon steel. Over

90% of all fasteners are made of carbon steel. In general, considering the cost of raw materials, non- ferrous should be considered only when a special application is required.

Tensile Strength

The most widely associated mechanical property associated with standard threaded fasteners is tensile strength. Tensile strength is the maximum tension-applied load the fastener can support prior to or coinciding with its fracture (see figure 1).

Tensile load a fastener can withstand is determined by the formula

P = St x As Example (see appendix for St and As values)

where 3/4-10 x 7” SAE J429 Grade 5 HCS

P = tensile load (lb., N) St = 120,000 psi

St = tensile strength (psi, MPa) As = 0.3340 sq. in

As = tensile stress area (sq. in, sq. mm) P = 120,000 psi x 0.3340 sq. in

P = 40,080 lb.