A325 or A490: key differences
| Characteristic | A325 | A490 |
|---|---|---|
| Product | Heavy Hex | Heavy Hex |
| Minimum tensile strength · inch series | 120 ksi | 150 ksi |
| Current specification | F3125/F3125M | F3125/F3125M |
| Specify | Type, dimensions, nut, washer, finish | Type, dimensions, nut, washer, permitted coating |
A490 is not an automatic replacement for A325. Joint resistance, ductility, components and installation must match the design. These values are neither allowable stresses nor tightening torques.
Heavy Hex, Twist-Off and Type
Heavy Hex identifies the head geometry. F1852 and F2280 identify Twist-Off configurations within F3125. Type 1 and Type 3 distinguish material types; Type 3 concerns weathering steel, not stainless steel.
Dimensions, thread and tightening
The inch Heavy Hex series covers diameters from ½″ to 1½″. Select length and thread position for the joint thickness and shear plane. Specify the required dimensional standard; A325M/A490M are not nominal conversions of inch products.
Nuts, washers and coatings
Specify ASTM A563 nuts and ASTM F436 washers compatible with grade, Type and finish. A coating used for A325 is not automatically permitted for A490. For pretensioned joints, request the assembly and relevant installation instructions.
Grade, type and style are separate fields
Identify the standard and edition, grade, type, style and dimensional system. Metric and inch configurations are maintained separately.
Twist-Off assemblies
F1852 and F2280 designations lead into the F3125 structure rather than duplicate pages presented as independent current specifications. Request the complete assembly specified for the project.
Grade 144: identify the specification
The 26 edition also covers the 144 ksi strength level. This does not establish equivalence with F3148: the specification and assembly configuration must be identified separately.