Basic Guide to Fasteners: Screws, Bolts, Nuts, Washers and Studs Explained

1. Bolts

Bolts are externally threaded fasteners designed to be used with a nut. They require a pre-drilled hole and are typically used where strong, long-lasting connections are needed. The bolts can be divided into ordinary ones and those with hinged holes according to the force of the connection. According to the shape of the head, it can be divided into hexagonal head, round head, square head, countersunk head, and so on. Among them, the hexagon head bolt is the most commonly used shape.

Common bolt types:

• Hex bolts: Most common for structural and mechanical use
• Socket head bolts: Used in machinery or tight spaces
• Cup head bolts: Rounded head, used in timber and metal

Tip: Match the bolt with the correct nut and washer for optimal performance.

2. Screws

Screws differ from bolts in that they usually create their own thread when driven into material. Screws are a common fastener that is widely used in daily life and production. The general material is plastic or metal, and the grooves engraved on the surface are called threads, which are cylindrical.

Common screw types:

• Self-drilling screws: Ideal for drilling into steel
• Wood screws: Coarse thread, ideal for timber
• Self-tapping screws: Cut their own thread in metal or plastic
• Machine screws: Used with pre-tapped holes or nuts

Tip: Choose the correct driver head (Phillips, slotted, hex) to avoid stripping.

3. Nuts

Nuts are internally threaded fasteners used in conjunction with bolts. When tightened together, they provide strong clamping force. 

The main difference between screws and bolts is that screws work individually. The thread matched with the screw is machined on the workpiece. But the bolt and the nut work together, and the thread matched with the bolt is machined on the nut.

They play similar roles but in different contexts. Bolts and nuts are pre-purchased standard parts, and the objects to be connected only need to punch a suitable through-hole for each connection. Screws can be used in situations where one of the objects to be linked cannot make a through-hole, then screw links can be used.

Common nut types:

• Hex nuts: Standard six-sided nut
• Nyloc nuts: Feature a nylon insert to prevent loosening
• Flange nuts: Have a built-in washer for greater surface area

Tip: Always use the same thread pitch and diameter as the bolt.

4. Washers

Washers are thin plates used to distribute the load of a fastener, reduce friction, or prevent loosening. Washers refer to the parts that are cushioned between the connected part and the nut. Usually a flat metal ring.

Common washer types:

• Flat washers: Spread load over a larger area
• Spring washers: Prevent loosening due to vibration
• Sealing washers: Provide a watertight seal (e.g. neoprene or rubber)

Tip: Use a washer to protect the surface of your workpiece.