Joints

Most products are made from more than one piece of material, so when the product is assembled or fabricated the pieces need to be joined.

Permanent and temporary joints

Permanent joints are intended to stay put. They may be assembled using adhesivesadhesive: A substance which bonds the surfaces of materials together., nails, rivets, or one of the heat processes of brazing, soldering or welding. Assembly jigsjigs: Devices for holding parts in position while they are being worked on or assembled. are often used to hold components in place while they are being joined. For example, the parts of a steel roof frame can be put into the jig and then welded together.

Temporary fixings usually involve components with a screw threadscrew thread: The projecting spiral rib of a screw or bolt., such as screws, nuts and bolts, or one of the many knock-down (KD) fixings.

Joining plastics

Plastic products are often moulded so they snap together. To make a permanent joint, a specialist adhesive, rivets, bolts or machine screws are used.