There’s no single, universal steel. The fact that steel is an alloy, a mix of different elemental minerals, practically guarantees that there is more than one way to make the stuff. As a result we have steel in a variety of compositions, each of which can withstand a certain amount of abuse and perform well under specific conditions. We assign grades to steel to make these differences clearer. Generally, the more carbon a steel fastener contains, the more it can be hardened, and the addition of other metals may provide other desirable qualities as well.
Let’s examine a few of the steel grades commonly assigned to bolts. Grade 4.8 steel is your generic hardware-store stuff — not particularly strong, but affordable and useful for general applications. Grade 12.9, 10.9, and 8.8 is considerably harder than Grade 4.8, so bolts featuring this grade of steel tend to see use in automobile construction and other industrial manufacturing. For components that face unusual stresses, such as car suspension systems, manufacturers turn to the even harder Grade 12.9 steel. When strength is the absolute top priority and flexibility doesn’t matter, you can go for the hardest possible steel, known as alloy steel. And as we discussed in a previous article, you can mix chromium into your steel to get stainless steel, though technically it’s not a grade.
Why wouldn’t you automatically choose the strongest grade of steel for all of your fasteners? Well, higher grades cost more, so you may be spending extra money on what amounts to overkill. And various kinds of steel have own advantages. Lower grade steel has more flexibility, while super-hard alloy steel can be extremely brittle. If you want to choose your grade of steel as wisely as possible, contact Mr. Metric and let us advise you on which fastener “makes the grade” for you.
Mr. Metric (a Mountz company) is the leading metric fastener specialist in North America. Well regarded as experts in metric, Mr. Metric is known for hard to find metric items at competitive prices. Contact Mr. Metric and let our staff help you with any metric nut requirements!
