ASTM A490

ASTM A490 and ASTM A490M are ASTM International standards for heavy hex structural bolts made from alloy steel. The imperial standard is officially titled Standard Specification for Structural Bolts, Alloy Steel, Heat Treated, 150 ksi Minimum Tensile Strength, while the metric standard (M) is titled Standard Specification for High-Strength Steel Bolts, Classes 10.9 and 10.9.3, for Structural Steel Joints.

Connection types

There are also three connection types defined:

• SC: A slip critical connection.
• N: A bearing type connection where the threads are on the shear plane.
• X: A bearing type connection where the threads are not on the shear plane.

Mechanical properties

These bolts are equivalent to ASTM A325 bolts in application and geometry, but are made to a higher strength. The imperial grades are made to the same strength specifications as ASTM A354 grade BD. The metric grades are made to the same strength specifications as ASTM F568M property class 10.9. Also, unlike their weaker counterparts they cannot be coated by hot-dip galvanization, mechanical deposition, or electroplating.

Because these bolts are designed to be used in structural applications the threaded length of the bolts are shorter to keep the threads out of the joint.

Imperial head markings and mechanical properties

Grade identification marking	Specification	Nominal size range [in]	Proof strength [ksi]	Yield strength (min) [ksi]	Tensile strength (min) [ksi]	Core hardness [Rockwell]
	ASTM A490 Type 1	​1⁄2–1-​1⁄2	120	130	150 minimum 173 maximum	C33–38
75px	ASTM A490 Type 2 (withdrawn)	​1⁄2–1
	ASTM A490 Type 3	​1⁄2–1-​1⁄2

Head markings and strengths for metric hex-head cap screws

Grade identification marking	Specification	Nominal size range [mm]	Proof strength [MPa]	Yield strength (min) [MPa]	Tensile strength (min) [MPa]	Core hardness [Rockwell]
	ASTM A490M Type 1	12–36	830	940	1040	C33–39
75px	ASTM A490M Type 2 (withdrawn)
	ASTM A490M Type 3