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Joints

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Joints between materials can be temporary or permanent. Joints can be formed with adhesives,frame joints [frame joints: joints in which the components meet at right-angles and fit tightly with each other ], brazed or welded joints, or with fastening components such as nails, screws, bolts, and rivets [rivets: metal or plastic fasteners. The rivet is inserted into holes in the materials to be joined and then end deformed to hold it in place. ].

Types of joint

Joints in wood can be made with screws, nails, glues and knock-down [knock-down: joint made up of separate components which are designed to be easily assembled and disassembled ] components, or with frame joints such as butt joints, halving joints, mortice-and-tenon, dovetail, and box joints.

Joints in metal can be made by brazing [brazing: joining two metal objects by melting a third metal with a lower melting point between them - fusing the two surfaces or edges together. Originally used brass as the 'filler metal' ], soldering [soldering: Joining two metal objects by melting a softer metal with a lower melting point between them - thus fusing the two surfaces or edges together. Soldering is a form of brazing. ], welding [welding: Joining metals by melting and fusing the adjoining edges or surfaces. ] or using rivets. Joints in plastics can be made with plastic adhesive, rivets, bolts or machine screws.

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 make use of adhesives [adhesives: substances which can bond the surfaces of materials together ], nails, rivets, or one of the heat processes of brazing, soldering or welding. Assembly jigs [jigs: 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 thread [screw thread: The projecting spiral rib of a screw or bolt. ], such as screws, nuts and bolts, or one of the many knock down fixings on the market.

nut bolt and washer

Adhesives

There are many types of adhesives to suit different materials. When you are choosing the right one for your product you will have to take into consideration the type of material, the strength of the bond required and the environment the product will work in - for example if you are gluing timber for outdoor use, you would not use polyvinyl acetate (PVA), because it is water soluble.

Double-sided tape is widely used in industry, many parts of aircraft are held together with double-sided tape.

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