Large Diameter Anchor Rods

The ASTM F1554 specification for anchor bolts ranges from ½ – 4”Ø in Grade 36 and 55 and ½” – 3”Ø in Grade 105. Other material specifications are available for diameters larger than what is covered by F1554, but in some cases they are not technically fastener specifications.

Grade	Identification	Size Inches
			36		1⁄2 – 4
			55		1⁄2 – 2
21⁄4 – 21⁄2
23⁄4 – 3
31⁄4 – 4
105		1⁄2 – 3

F1554 Grade 36 – A36

F1554 Grade 36 covers anchor bolts through 4” in diameter that have minimum yield strength of 36 KSI.  For anchor bolts requiring a diameter larger than 4” and approximately Fy = 36 ksi, ASTM A36 may be considered. ASTM A36 is a general steel specification that covers carbon steel shapes, plates, and bars – so it is not necessarily a fastener specification.  Potential issues regarding ordering fasteners to standard steel specs can be found in this previously published FAQ.

F1554 Grade 55 – A572 Grade 50

F1554 Grade 55 covers anchor bolts through 4” in diameter that have minimum yield strength of 55 ksi. For anchor bolts requiring a diameter larger than 4” and approximately Fy = 55 ksi, ASTM A572 Grade 50 may be considered. ASTM A572 is a common steel standard for high strength, low-alloy structural steel shapes, plates and bars.  Potential issues regarding ordering fasteners to standard steel specs can be found in this previously published FAQ.

F1554 Grade 105 – A193 Grade B7

F1554 Grade 105 covers anchor bolts up to 3” in diameter that have minimum yield strength of 105 ksi. For anchor bolts requiring a diameter larger than 3”, ASTM A193 Grade B7 may be considered. ASTM A193 Grade B7 is a fastener specification for alloy steel bolts to be used in high temperature or high pressure service.  For A193 Grade B7, the material strength decreases as the diameter of the steel round bar increases. This means the mechanical properties are not directly comparable for F1554 Grade 105 in 3”Ø to A193 Grade B7 in 5”Ø.  The standard thread pitch for A193 Grade B7 in diameters larger than 1” is 8UN.  If A193 Grade B7 is being used as an anchor bolt, UNC thread pitch should be considered and is required for galvanized anchor bolts in diameters larger than 1½”.

Other Considerations

Other fastener specifications such as ASTM A449 (heat treated medium carbon or alloy steel) and ASTM A354 Grade BD (heat treated alloy steel) have maximum diameters of 3” and 4”, respectively. If diameters larger than what the specifications allow are required, a 4140 Q&T (quenched and tempered) material may be used.  In this situation, the purchaser would need to specify the mechanical properties prior to purchase.