I have found over the years that there are many people out there who can weld. Some went to school. Some learned on their own in a garage somewhere. Some of those who say they can weld, don't weld very well at all.
Because of this, I thought I would put together some information to help those of you unfamiliar with welding symbols if you're trying to follow a drawing. Elements Of A Welding Symbol:
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A welding symbol may include the following elements: Reference Line Arrow
Basic Weld Symbol
Dimensions & Other Data Supplementary Symbols
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Finish Symbols Tail
Specifications, Process, Or Other References
Reference Line:
A reference line is a horizontal line with all the other required information drawn on or around it. It must be placed on the drawing near the joint it describes. Arrow:
The arrow is the other required part of a welding symbol and is placed at one or the other end of the reference line and connects the reference line to the joint that is to be welded.
Quite often, there are two sides to the joint to which the arrow points, and therefore two potential places for a weld. For example, when two steel plates are joined together into a T shape, welding may be done on either side of the stem of the T.
The weld symbol distinguishes between the two sides of a joint by using the arrow and the spaces above and below the reference line. The side of the joint to which the arrow points is known as the arrow side, and its weld is made according to the instructions given below the reference line. The other side of the joint is known as the other side, and its weld is made according to the instructions given above the reference line. The below and above rules apply regardless of the arrow's direction.
Basic Symbols:
Each type of weld has its own basic symbol, which is typically placed near the center of the reference line (and above or below it, depending on which side of the joint it's on). The symbol is a small drawing that can usually be interpreted as a simplified cross-section of the weld. In the descriptions below, the symbol is shown in both its arrow-side and other-side positions.
Fillet Weld
Groove Welds
Plug Weld
Weld All Around & Field Weld:
There are two other elements that may be seen on the reference line that provide information about the weld. One is a circle around the place where the leader line connects to the reference line and indicates the weld is “all around”. This means the weld extends all the way around the joint the arrow is pointing at.
The all around element is only used when it is possible to weld all the way around a single surface (see below).
The other element seen on the reference line resembles a flag and is located where the leader line joins the reference line. This element is called a \the weld will be done in another location. For instance, this weld may be applied at the job site not in the shop. Sometimes clarification will be given in the welding symbol tail or as a specification on the print.
Field Weld Symbol
Fillet Weld:
The fillet weld (pronounced \As its symbol suggests, the fillet weld is roughly triangular in cross-section, although its shape is not always a right triangle or an isosceles triangle. Weld metal is deposited in a corner formed by the fit-up of the two members and penetrates and fuses with the base metal to form the joint. (Note: for the sake of graphical clarity, the drawings below do not show the penetration of the weld metal. Recognize, however, that the degree of penetration is important in determining the quality of the weld.)
The perpendicular (straight up and down) leg of the triangle is always drawn on the left side of the symbol, regardless of the orientation of the weld itself. The leg size is
written to the left of the weld symbol. If the two legs of the weld are to be the same size, only one dimension is given; if the weld is to have unequal legs (much less common than the equal-legged weld), both dimensions are given and there is an indication on the drawing as to which leg is longer.
The welding symbol above shows that the weld is to be done on the other side and the thickness of the weld is 5/16.
The length of the weld is given to the right of the symbol.
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