Made of Grade B7 steel, these screws are nearly twice as strong as Grade B8 and Grade B8M stainless steel screws. Also known as pressure bolts, they meet the high-pressure and high-temperature regulations of ASTM A193 and are used to secure pressure tanks, valves, and flanges. The head is 10% wider than a standard hex head, so it spreads force over a larger area, and you can tighten these screws with more torque. Steel screws are best for dry environments, since moisture will cause them to rust. They require little surface prep before applying a finish, so you can apply your own paint or coating. Length is measured from under the head. Use these screws with ASTM A194 nuts and ASTM F436 washers.

All screws meet ASME B18.2.1, which means they’re made to strict dimensional standards.

Partially threaded screws have a precisely measured unthreaded section under the head, called a grip. It’s stronger than the threaded section, so you can place it in joints exposed to sideways force.

Match the thread spacing of mating components. Fine threads are closely spaced to prevent loosening from vibration.