Sheet metal parts are seldom used alone. They are usually joined to form a component with a specific function. And even if the component consists of only one single part, it often features elements that need to be joined. Device enclosures, covers, containers, cabinets and housings, generally need to be joined at their corners.
Design engineers have to take into account the wide range of factors when deciding which technique to use. The first question that engineer faces concerns the basic characteristics of the joint, whether will it be permanent or non-permanent. The latter can be only made by mechanicals means. This kind of joint is used whenever access to the enclosed parts is needed for maintenance, repairs, upgrades or other reasons.
Among the various joining methods, you can find conventional welding techniques such as MIG and MAG welding and familiar faces like press-in fasteners.

Threaded fasteners

Threaded fasteners are type of fasteners among many press-in fasteners which are used for joining separate sheet metal parts into components.
Using threaded fasteners is probably one of the most familiar joining techniques. It is also the only one that produces an extremely strong joint that can still be taken apart and reassembled if needed. Threaded fasteners are frequently found on enclosures or covers that may need to be opened up later on. Good examples of such components are a computer and other electronic appliances housings or back panels of TVs and other electronic devices.
For the screw joint to hold together, the length of the thread should be equal to or greater than the diameter of the corresponding screw. There is a variety of ways of fabricating threads on sheet metal and many different types of threaded fasteners to choose from. Some of the most common types are:

• Press-in threaded inserts
• weld nuts

Holes are punched into the sheet wherever the threads are needed, and threaded insert is either welded to or pressed into the material. This technique permits the use of large thread diameters on thin sheets. Once the insert has been installed, the area no longer has to be accessible from both sides.

Tapping
Blind rivet nuts
Self-tapping screws
Countersunk screws