Mechanical requirements by diameter
Inch grades are published in ksi and metric classes in MPa. The other column on every row is a conversion at 1 ksi = 6.894757 MPa, rounded to the nearest whole unit - it is arithmetic on the published figure, not a second published figure.
The head marking
Six radial lines with the manufacturer's identifier, or marked A449.
A449 is the general-engineering counterpart of A325 and covers sizes A325 does not. Its head marking is not a reliable way to tell it from a Grade 8 bolt, so read the paperwork.
Count the radial lines and add two. That rule identifies exactly two grades - SAE Grade 5 with three lines and SAE Grade 8 with six - and it fails everywhere else. Grades 1, 2 and 4 carry no marking at all, so an unmarked head is not evidence of Grade 2; it is evidence of nothing, and unmarked hardware that meets no standard looks exactly the same. ASTM grades are stamped with the specification (A325, A490, BC, BD, 307A) rather than lines, and metric classes are stamped with the class number. Four marking systems share one bin.
Material and where it is used
Medium carbon steel, quenched and tempered. General high-strength bolting outside the structural A325 scope, and sizes above 1-1/2 in.
Three bands, and the drop is steep: a 2 in A449 bolt has less than two thirds the proof stress of a 1 in one.
One chart gives the hardness of the largest band as Brinell 183 to 235 rather than Rockwell B91 to B100. Those are different scales rather than different requirements.
Frequently asked questions
How strong is a ASTM A449 bolt?
Over 1/4 in through 1 in, ASTM A449 requires a minimum tensile strength of 120 ksi (827 MPa), a minimum yield of 92 ksi (634 MPa) and a proof load of 85 ksi (586 MPa). The requirement changes in the larger sizes - 3 diameter bands are published in all.
What does a ASTM A449 head marking look like?
Six radial lines with the manufacturer's identifier, or marked A449.
What is a ASTM A449 bolt made of?
Medium carbon steel, quenched and tempered. General high-strength bolting outside the structural A325 scope, and sizes above 1-1/2 in.
Does ASTM A449 get weaker in larger sizes?
The requirement changes with diameter. 1/4 in through 1 in: 85 ksi (586 MPa) proof; Over 1 in through 1-1/2 in: 74 ksi (510 MPa) proof; Over 1-1/2 in through 3 in: 55 ksi (379 MPa) proof. Quoting one figure across the whole range gets part of it wrong.
What this section covers
Twenty-two grades and classes: the SAE J429 inch grades, five ASTM specifications and the ISO 898-1 property classes. It is not every grade in circulation. Stainless classes (ISO 3506 A2 and A4, ASTM F593), the ASTM A193 and A320 high and low temperature grades, ASTM F1554 anchor rod grades and SAE grades 3, 5.1 and 8.1 are not carried here.
Where these figures come from
Dimensions are as defined by ASTM A449. This site is an independent reference and is not affiliated with, endorsed by or approved by any standards body.
Every value on this page was cross-checked against 5 independent published sources: