Bolt Shear Strength Considerations
Question: What is the shear strength of carbon steel bolts?
Answer: First, unlike tensile and yield strengths, there are no published shear strength values or requirements for ASTM specifications. The Industrial Fastener Institute (Inch Fastener Standards, 7th ed. 2003. B-8) states that shear strength is approximately 60% of the minimum tensile strength.
“As an empirical guide, shear strengths of carbon steel fasteners may be assumed to be approximately 60 percent of their specified minimum tensile strengths. For example, an SAE grade 5 hex cap screw has a specified minimum tensile strength of 120,000 psi. Therefore, for design purposes, its shear strength could be reasonably assumed to be 70,000 psi.”
Quick Tip: For instructions on how to calculate the strength for your bolt, see Calculating Yield and Tensile Strength.
It is important to understand that some imported fasteners, like lag screws, are typically ungraded. Since they are not manufactured to any specific grade, it is impossible to determine any strength characteristics associated with them unless you have them strength tested at a laboratory. For applications where shear will occur in the unthreaded portion the nominal diameter should be used to calculate the value. Whereas, if the shear area is in the threaded section the minor diameter should be used.
AISC provides published values for ASTM A325 and A490 structural bolts listed in Specifications for Structural Steel Buildings under Table J3.2 (16.1-104).
Although, the Strength by Grade Chart has no shear strength information, it shows the strength requirements of common ASTM and SAE grade construction fastener specifications.