Most of the welds that we have to make fall into five general categories. Each one of these individual joint categories have many variations onto the basic unit. Understanding these five and being able to complete Welds in all positions is a good starting point for everyone learning how to weld. The five basic weld joints include the butt joint, the lap joint, the tee joint, the corner joint, and the edge joint.
The butt joint occurs when two members are placed side-by-side or butted together. The weld is made along the seam that adjoins the two adjacent pieces. Depending upon the thickness of the materials, the edge of the butt joint maybe squared, beveled or have some other type of preparation done to it prior to fit up and welding. The butt joint can be welded on one side or both sides depending upon the requirements in the drawing or welding symbol. The butt joint is considered a groove type weld.
The lap joint is formed when two pieces are placed on top of each other overlapping each other for a given distance along their edge. In most instances we do not see edge preparation done on a lap weld. A fillet weld is placed in the seam between the two overlapping members. Just as with the butt joint, the weld can be made on one side or both sides depending upon the requirements in the drawing or welding symbol. The lap joint can contain one or more welding passes. The lap joint is considered a fillet type of welding joint.
A Tee joint is formed when two members intersect at 90° and the edges come together in the middle of a plate or component. A Tee joint also will be formed when we place a pipe or tube onto a baseplate. The all-around weld of the pipe to the baseplate is considered a tee joint. A fillet weld is placed between the two members depending upon the size and requirements of the drawing. As with the other joints the welds can be made on one side or both sides. Sometimes it requires more than one will pass to create concise fillet weld needed. Just like the lap joint, the Tee joint is also considered a fillet type weld joint.
The corner joint is similar to a T joint but instead of the members coming together in the middle of the plate or component the corner joint has two pieces that intersect at 90° at the edge of the joint or material. A fillet weld is generally made in the area where the two plates or members intersect. There are a couple of variations on the corner joint, one being called an open corner where the fillet weld is made on the outside edge. Another is called the closed corner where the weld on the outside is much more similar to that made on the square butt joint. Most people consider the corner joint to be a fillet type will joint. As with all the other welds, the weld can be made on the near side or the other side.
And finally the fifth of the five basic will joints is what we call the edge joint. Two members have their surfaces placed parallel to each other creating a seam or edge area were welding can occur. The edge weld is considered a groove type weld. We frequently see the edge joint applied to sheet-metal parts were the edge has been flanged up or formed such that a weld needs to be made to join adjacent pieces. Just with all the others the welds, it can be made on the nearside the other side or all the way around the perimeter depending on the use and service conditions.
Being familiar with the five basic weld joints and being able to weld those up in a number of different positions will make you a much better fabricator and welder and make you more valuable to your employer or your own personal fabrication business.
Check out the Longevity website (www.longevity-inc.com) or YouTube channel (www.youtube.com/longevitywelding) for more details and information about equipment for different welding and cutting processes. Longevity has the right machine for your exact application, so take a look and choose what is the best fit for your materials, product and needs.