A Beginner’s Guide to Reading Welding Symbols

Welding symbols are most commonly applies to drawings and when interpreted correctly, efficiently controls the welding of a joint. The symbols offer a consistency that helps bridge the gap between the engineers who draw the diagrams and the construction workers who work on the site. However, though the standard system of signs remains similar it is essential that there exist some flexibility within the current system so that they can be used over a wider set of fields. As when it comes to welding, the most important factors worth considering are cost and equipment. Often, manufactured welds differ in terms of performance thus highlighting the importance of joint geometry.

Types of Symbols

The Arrow

The Arrow is the primary element among welding symbols. The arrow points to the joint that must be welded. The body of the arrow must not touch or run over any part of the drawing at hand, nor should it be merely a horizontal line. The direction in which side the arrow points is termed as “arrow side” with respect to the joint and the opposite direction as “other side”.

Given the complexity of modern architecture, more often than not there is a shortage of space on the paper to draw symbols. Thus, to efficiently use space more than one arrow can be used in a single welding symbol if all the subsequent joints are to be welded in the exact same manner. One can also use a multiple arrow symbol to show a change in direction of the geometry.

The Reference Line

The Reference Line is essentially a straight line drawn horizontally and connected to an arrow. When it comes to imparting information along with the symbols, all instructions for the “arrow side” are written below the reference line and all instructions regarding the “other side” are placed above the line. The system of instruction does not change with respect to the direction of the arrow or the angle of the reference line with respect to the drawing. It is important to note that in the event of multiple welds on subsequent joints, the reference lines do not indicate the sequence of the welding to be undertaken.

The sequence in a welding operation can be represented by a multiple-reference line i.e. two or more reference lines connected to the same arrow. The same symbol can also be used for any non-destructive action other than welding.

The Tail

The tail symbol is represented as < or > symbols which are used at the end of the reference line opposite the arrow. The process that is to be followed while welding the joint is often written through designated letters at the end of the tail.

Groove Welds

The Groove Weld symbol though little used, is extremely important in terms of function. This symbol is added below or above (as per usage) the reference line as a note to specifically weld only a previously instructed side of the reference line. The weld symbol can also be placed both above and below the line to represent a double weld.

Complete Joint Penetration

There are a number of ways to represent the complete joint penetration. The most common way to use this symbol is to use an arrow, the reference line and to write CJP in the tail end of the symbol.However, since the symbol is essentially simplistic in nature there are no extra details to instruct how to go about the task.

Fillet Welds

These types of welds are extremely important when it comes to industries which produce boilers. The symbol is represented with a right triangle which is placed on the reference line and with the perpendicular of the triangle being on the left. The fillet weld differs from the groove type in two ways mainly. Firstly, fillet weld may not extend to the entire length of the joint and this is indicated by noting down the dimensions written beside the filet weld symbol.In the absence of any such dimension the entire length should be welded. Secondly, fillet weld are not continuous welds and to such effects even the dimensions are mentioned.


The delicate and intricate process of welding cannot take place unless explicit information if conveyed from the architect to the works men. It is to bridge this communication gap that it is essential to be acquainted with a common system of symbols. Though now predominantly used in the United States, the method of symbolic representation is spreading fast.

  • December 22, 2016
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