Mechanical Fixings
Mechanical fixings join parts together by mechanical action through friction (screws and bolts) or deformation (rivets). These are different to welding (thermal) and glues (chemical). There are two types of riveting; pop riveting and solid riveting, these are covered in another part of the website.
Fastening types
As you can see in the image, there are a wide range of different mechanical fastings. These can be divided into 'screws', which cut their way into the material, and bolts which either fit into a pre-threaded hole or require a nut to secure them in place.
Self drilling and thread cutting screws - Self Tapping
Screws are more commonly associated with wood but 'self tapping' screws are often used to join sheet metal parts and thin walled sections together. These can provide a secure joint and often don't require a pilot hole. Metal roofing sheets can be secured in this way to either wooden or steel rafters without the need to pre-drill any holes. This makes the process efficient.
Nuts and Bolts
Nuts and bolts are often used to join parts together. This type of fixing can be very strong and the joint can also be easily disassembled for adjustment or maintenance. A nut and bolt are usually combined with a washer, this helps spread the load of the nut and bolt and prevent damage to the surface and also reduces the chance of the nut coming loose.
There are many different types of bolt, nut and washer for different applications. For example nuts which 'lock' and washers which stop the nut vibrating loose. Different Heads are also used along with different ways of 'driving' the nut and bolt together.
