Threaded Fasteners Guide: Common Types of Threaded Fasteners and Their Uses | CNCLATHING

2021.7.5

Fasteners are essential in mechanical applications where requiring join two or more objects together, with or without threads. In this guide, we’ll focus on fasteners with threads, there are different types of threaded fasteners, working in similar or different way. What are threaded fasteners and their types? Keep reading for the details.

What are Threaded Fasteners

Threaded fasteners are usually identified by its internal or external thread, which is a spiral ridge on a cylindrical shaft or inside. The thread is used to convert a torque or rotational force into a linear force. When the internal and external threads interact, they convert rotational motion into linear motion. The most common types of threaded fasteners are the screw, nut and bolt, possibly involving washers.

Different Types of Threaded Fasteners and Their Uses

Although threaded fasteners functions for one single purpose: to join two or more pieces together, there is a multitude of designs and sizes to choose from, which makes them suit for various applications and industries. 

1. Bolt 

Bolt is used to connect two thin parts. There is a through hole on the connected part. There is a gap between rod and hole of through bolt. Its processing requirement of through hole is general, the structure is simple, the assembly and disassembly are convenient. It is widely applied. Reamed hole bolt (GB/T 27) hole and screw often adopt transitional fit such as H7/m6, H7/n6. This kind of connection can accurately fix the relative position of the connected parts. It is suitable for bearing lateral load, but the CNC machining accuracy of the hole is relatively demanding, and it is often used with drills and reaming.

2. Stud Bolt

Stud bolt is used to connect a thick piece, not suitable to connect with bolts. The thick parts need to be disassembled frequently with poor strength. A threaded hole is machined on a thick part, a smooth hole is machined on a thin part, a bolt is screwed into the threaded hole, and a nut is used to tighten the thin part.

3. Screw

Bolts (or screws) are directly screwed into the threaded holes of the connected parts without nuts. The structure is simpler and more compact than that of stud bolts. It is used for the thicker one of the two parts, but disassembly is not required to avoid damage to the threaded hole.

4. Set Screw

The end of the thread screwed into the threaded hole of the part is used to withstand the surface of another part or into a recess on the other part to fix relative position of the two parts. This connection is simple, and some parts can be arbitrarily changed in the circumferential or axial position for adjustment, such as fixing of electrical switch knobs.

5. Countersunk Screw

Countersunk screw is used for low strength requirements, and the thread diameter is less than 10mm. The head of the screw or part of it sinks into the connected part. This structure is mostly used in a flat outer surface, such as a panel.

6. Self-tapping Screw

Self-tapping Screw is used for weak connection. But generally speaking, the bottom hole should be made in advance. If a self-drilling and self-tapping screw with a drill is adopted, there is no need to prefabricate the bottom hole used for non-ferrous metals, wood, etc.

7. Wood Screw

Wood screw is used for wooden structures. Given that the hardness of the material and the length of the wood screw, wooden parts may not be prefabricated or prefabricated with a certain size and depth.

8. Self-tapping Lock Screw

The thread has an arc-shaped triangular interface, and the screw is hardened on the surface and can be screwed into a prefabricated hole of metal material and be extruded to form an internal thread. The internal thread formed by extrusion is more than 30% stronger than the cut one. The small tensile strength of the screw is 800MPa. Self-tapping locking screws have low tightening torque and high locking performance. They have been widely used in household appliances, electrical engineering and automobile industries.

9. Fastener-Assembly

Washers and external threaded fasteners are assembled and supplied as a set after being produced by a standard professional factory. This kind of connector is convenient, time-saving, safe and reliable, used in tight connection, such as terminal posts in electrical cabinets.