Select the Right Grade With the Help of Your Fastener Distributor

In almost every application a fastener is used to clamp components together. There are the odd applications where a fastener needs to function as an axle or lever support, but for the most part fasteners act as clamps. When it comes to grade selection your fastener distributor is the best source of direction. They will be able to specify and source out the best grade for your application.
Understanding the Different Grades
There are three basic SAE grades to choose from:

• Grade 2 – comes in diameters from 1/4" to 1 1/2" and is made from medium to low carbon steel materials
• Grade 5 – comes in diameters from 1/4” to 1 1/2" and is made from medium carbon, tempered and quenched steel
• Grade 8 – comes in diameters from 1/4” to 1 1/2" and is made from alloys that include medium carbon steel, also tempered and quenched

Tensile strengths across these three grades vary from 60,000 psi to 150,000 psi, with proof loads spanning 33,000 psi to 120,000 psi.
Your fastener distributor will also have corresponding property classes for metric fasteners. Property class (or P.C.) 5.8 lines up with grade 2 types, P.C. 8.8 is similar to grade 5 and P.C. 10.9 offers the same strength as grade 8.

Cost Comparison
Grade 2 or P.C. 5.8 fasteners are the least expensive of the categories listed above. But when considering the holding power, it may be more affordable to opt for stronger grades.
Costs depend more on the diameter of the fastener. Therefore, if you can find higher grade fasteners with smaller diameters that provide the same proof load as lower grade fasteners with larger diameters, you are better to opt for the high grades. They will be cheaper over all, yet provide for the same level of proof load.
Quick example:

• Grade 2 fastener at 3/4" diameter provides an 18,400 pound proof load
• Grade 5 fastener at 5/8” diameter provides an 19,200 pound proof load AND is less expensive than the Grade 2 example

You will spend less on the stronger fastener in this case, and can actually depend on it to deliver the same level of performance.
A fastener distributor will be happy to work through these calculations with you, with the aim of finding the best fastener specifications possible for your application.