Grades & Standards


The vast bulk of our steel products are mild steel, also known as low-carbon steel. Our screws and bolts are comparable, then, to what you will find in the bins at your neighborhood hardware store or home center. Mild steel is affordable, weldable and machinable, making it ubiquitous in our lives. 


There are thousands of different kinds of stainless steel, in various families and grades. In the US, however, two main grades dominate for consumer products: SAE 304 (also known as 18-8) and SAE 316. All of our stainless steel products conform to one of these grades. Blacksmith Bolt makes no claim about the suitability of these products for various applications.


Bolts are subject to a dizzying array of classifications and grades. Generally speaking, however, most all-purpose bolts are referred to by the SAE designations of Grade 2, Grade 5 and Grade 8. All of our bolts are Grade 2, i.e. they are suitable for most common household and light commercial applications.

Grade 5 bolts, by extension, are hardened and work for most automotive and machinery applications, and Grade 8 bolts are even stronger, for critical applications like heavy trucks and industry.

Again, this is a simplification. Blacksmith Bolt makes no claims regarding the suitability of its bolts. For critical applications and manufacturing documentation we suggest you talk with our friends at Portland Bolt.


We are often asked about the "A307" designation stamped on the heads of machine bolts and carriage bolts. A307 is an ASTM designation for everyday medium strength bolts. Our machine bolts and modern carriage bolts meet the A307 designation and are stamped as such. We have our lag bolts and traditional carriage bolts made exclusively for us without the A307 head stamp, because it detracts from the clean lines of the bolt. They are, however made from the same mild steel (C1006 or C1008) as stamped A307 bolts, in an ISO-certified factory that makes millions of A307 bolts. They are equivalent.