People use these names interchangeably all the time, and honestly, at the counter we know what you mean either way. But there is a real difference, and it comes down to one thing: how the fastener is held and tightened.
A headed fastener that passes through the parts and is held by a nut on the other side. The bolt usually stays still while the nut is turned to clamp things together.
A headed fastener that threads into the material itself — a tapped hole, or threads it cuts as it goes. No nut needed. You turn the screw by its head to drive and tighten it.
A length of threaded rod with no head — threaded on both ends or all the way along. One end anchors into a part or stays fixed; nuts go on to clamp. Common where you need to slide a part on, then secure it.
Here’s the gray area. The same part — a hex-headed fastener with a partially or fully threaded body — gets called a hex bolt by most people and a hex cap screw in catalogs and standards. Technically the difference is about how it’s used (with a nut = acting as a bolt; threaded into a tapped hole = acting as a screw), not about the part itself. That’s why one fastener can wear both names.
The takeaway: don’t overthink it. If you describe what you’re doing — “going through with a nut” or “threading into a block” — we’ll match you to the right part regardless of which word you use.
One thing that does matter: whether you need a nut with it. Tell us if you’re using a nut (and whether you need washers too), and we’ll make sure the threads and grade all match across the set.
Ask yourself: what holds it tight? If the answer is a nut on the far side, you’re using it as a bolt. If it threads into the part itself and you turn the head, it’s a screw. If it has no head and clamps with nuts on the ends, it’s a stud. That one question sorts out almost every case.
Once you’ve got the type, the rest is size, thread, grade, and finish. These pick up from here.
