Welding joints: Some common welding joints are shown in Fig. 1. Welding joints are of generally of two major kinds namely lap joint and butt joint. The main types are described as under.
Lap weld joint:
Single-Lap Joint This joint, made by overlapping the edges of the plate, is not recommended for most work. The single lap has very little resistance to bending. It can be used satisfactorily for joining two cylinders that fit inside one another.
Double-Lap Joint This is stronger than the single-lap joint but has the disadvantage that it requires twice as much welding. Tee Fillet Weld This type of joint, although widely used, should not be employed if an alternative design is possible.
Fig. 1 Types of welding joints
Butt weld joint:
Single-Vee Butt Weld: It is used for plates up to 15.8 mm thick. The angle of the vee depends upon the technique being used, the plates being spaced approximately 3.2 mm.
Double-Vee Butt Weld: It is used for plates over 13 mm thick when the welding can be performed on both sides of the plate. The top vee angle is either 60° or 80°, while the bottom angle is 80°, depending on the technique being used.