Understanding the Basic Welding Symbols

Last Updated on May 2022


Do you want to take your welding prowess to the next level? If you are more than just a hobbyist welder, and are keen to learn a lot more about welding and its various symbols, then hurrah! You couldn’t be at a better place. Understanding weld drawings is never easy, even the most experienced welders love refreshing their memories every once in a while to avoid being caught off guard.

In case you are considering a welding career preparing for a test on welding symbols, this user guide is also ideal for you. We know that 75% of professional welders learn welding symbols along the way- exactly why we want to equip you with the additional information that will get you to that desirable 25% of highly knowledgeable welders.

The Main Welding Symbols

Now, to help you out in your different welding projects, we will discuss the main and most common welding symbols that you are likely to encounter in your welding projects.

Base Platform

This symbol helps to display the various characteristics as well as surrounding details of the weld you are working on. It comes in three main parts as labeled above

  1. Arrow Line- This section symbolizes your weld`s general location
  2. Reference Line- This is the section where more details are provided regarding the weld type and location
  3. Tail- Complementary details are usually placed here. The details you can expect to spot here include material types, welding standards and the ideal welding process.

The Drawing System

The base platform comes in two main systems that are interpreted differently. You won`t have both systems located on a single drawing. Below is a pictorial interpretation of the two systems.

 Base System A

Base system A usually has dash lines that run beneath the reference line. As per the image below, the weld should always be on the arrow`s opposite side when the weld symbol is located on the side of the dashed line. In case the welding symbol is located on top of the reference line, then you need to place the weld on the arrows side as indicated below.

Base System B

Base system B lacks the dashes underneath the reference. Thus, in Base B, the weld is usually located at the arrow`s side when the welding symbol is put beneath the reference line. In case the symbol is above the reference line, then you should place the weld on the arrow`s opposite side as indicated in our image below.

Base Butt Symbols

Base butts are usually distinguished by how they but up from their two ends. Let`s take a look at some of the main symbols

Single-Sided Butt Welds

These joints are easy to detect since they have one-sided symbols. The symbols reveal the ideal weld prep details. Other symbols tell more about the required type of welding as shown in the below image.

Let`s indulge further on these symbols

Square Butt: Both of its ends are square, which is represented by the two square angles on the symbol. This joint doesn’t have a weld prep.

Single V Butt: This joint comes with a 45 degree weld prep on each sides plate as well as full depth. The plates form a V shape once joined as indicated.

Single V Butt with Broad Root Face: Has a 45 degree angle but only reaches 75% plate depth, thus leaving a section below. This joint forms a Y shape.

Single Bevel Butt : Has a 45 degree angle cut on one side which goes the full depth while the other side maintains a square shape as displayed.

Single Bevel Butt with Broad Root Face: This weld prep resembles a lowercase ‘r’ but without the arc. It has a 45 degree bevel that doesn’t run the plate and a square end.

Single J Butt: One of the plates has an arc that runs partway through the plate while the first end is square. These two shapes form an arched ‘r’ when joined as indicated in the symbol.

Single U Butt: Both the plates have their corners cut and they run three quarters down the plate forming a u partway.

Double-sided Butt Joints

Unlike single sided joints, these butt joints are prepped and welded on both sides as you can see in the image below.

Double-sided V Butt : All the ends of the plates have 45 degree bevel cuts and meet to form a point at the middle point of the plate. The meeting of the various joints creates an x symbol as is evident in the above picture.

Double-sided U Butt: Both the sides have quarter moon cuts thus creating two U`s, one on top and the other inverted at the bottom.

Double Sided Bevel Butt:  The plates join to make a K as one side lacks weld prep, thus allowing for square corners. The other side, however, has two bevels cutting in at 45 degrees across the middle.

Other Symbols

There are several types of symbols that professional welders should look to know and understand. Below is a list of other base symbols, other than butt welds, that you probably need to know.

Fillet:  Fillet symbol is represented by a right-angle triangle. This is because most fillet joints are usually at right angles to one another between two plates.  The fillet is often close to the 90 degree joint.

Resistance Spot: Indicates when two plates are conjoined as a result of electric heat using a spot welder. The symbol of a resistance spot is circular, similar to a spot weld.

Plug: The symbol represents a situation when a holed plate sits on a plain plate. The plug weld will fuse the two plates and ensure an internal weld fills the hole entirely.  The symbol represents the top plate`s cross-sectional view.

Resistance Seam: The resistance seam is very much similar to the resistance spot symbol only that it has parallel lines that run through the circle. Instead of creating a single spot, resistance seam creates a spread out seam weld.

Supplementary Symbols

Supplementary symbols, as the name suggests, are additional base symbols that are crucial in clarifying the required type of weld. They reveal properties like the how to make a weld, its characteristics and the ideal welding location as well as the required finishing features as shown in the image below.

Flush Finish: Indicates that the final weld requires grounding back or adequate machining to return it to the desired plate level. It is represented by a straight line to showcase how the final weld should look like.

Concave: The concave symbol indicates that the weld should have an inward curve similar to a bowl`s inside once completed. This is a common type of finish when using fillet welds.

Convex: Convex finishes curved outwards similar to balloons.

Racking Weld: Common symbol that is used for U or V weld preps that require initial welding at the base before the main welding. This highlights that you might be required to pre weld the base to prevent exposing the weld to too much heat thus ruining the entire component.

 Weld Entirely Around

The weld entirely around symbols help to notify you of the exact areas that require welding as you can see in the below image.

Weld Between Points: The illustration will indicate two points like C and D, that need welding done between. The arrow between the two letters highlights that the weld should run the entire length from the start point to the designated point.

Weld on site: This is a pretty straight-forward symbol that tells you to weld at the site and not at your workshop or garage.

Staggered Intermittent Weld: This symbol notifies you that the welds should be intermittently staggered from one side to the next. You should weld each side full length before starting with the smaller portions.


Understanding the main symbols for welding, as you can see, is not a walk in the park. Although most experts have probably come across most of these symbols, not all understand what some complex symbols mean.

While you can still weld without knowing what some of these symbols mean or refer to, having an understanding of them can help you save time and improve the outcome of your welding projects. You don’t have to learn each of these welding symbols at once, we believe in practice makes perfect.

Instead, you can try working with each of these symbols gradually at the workshop. However, be sure to keep an eye on cautionary symbols like the flag that notify you if the project should go on at site or inside your warehouse.

Most welding machines usually come with usage charts on the inside of the frames, knowing these symbols means that you will be able to understand the usage of such devices with ease. It also gives you additional power when selecting the best welding machines for your intended use.

Having discussed the main symbols associated with the satisfying task of welding, we believe that you should be well placed to learn and understand them with ease. Remember to practice patience as you continue with your welding projects as you will probably run across these symbols at some point in your welding adventure.

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