How to Read a Welding Symbol: A Plain-Language Guide for Welders
Welding symbols are the shorthand that engineers use to tell welders exactly what to do at each joint on a drawing. If you have ever looked at a fabrication print and felt lost, you are not alone. But learning how to read welding symbols is not as complicated as it looks. Every symbol follows the same basic structure, and once you understand that structure, you can decode any print that lands on your bench.
This welding drawing symbols guide breaks down the parts of a welding symbol, the most common weld types, and how to read the information that tells you where, how big, and what process to use.
The Basic Structure of Every Welding Symbol
Every welding symbol is built on the same framework. Once you recognize the parts, the rest is just reading the details attached to them.
The five core components are:
- Reference line: the horizontal line that anchors everything. All weld information hangs off this line.
- Arrow: points from the reference line to the joint that needs welding.
- Weld symbol body: a small shape on or near the reference line that tells you the weld type (fillet, groove, plug, etc.).
- Tail: an optional section at the end of the reference line that holds extra instructions like welding process, filler metal, or inspection notes.
- Supplementary symbols: additional marks that indicate finishing (flush, convex, concave), field welds, or all-around welds.
Understanding weld symbol meaning in blueprint drawings starts with recognizing these five parts. Everything else is detail.
Arrow Side vs. Other Side
This is where most beginners get confused. The side the arrow points to is the “arrow side,” and its instructions go below the reference line. The opposite “other side” instructions go above the reference line. This rule applies no matter which direction the arrow points. Getting this wrong means welding on the wrong side of the joint.
Common Weld Symbols and What They Mean
Here is a welding symbol chart covering the weld types you will see most often in shop and field work:
| Symbol Shape | Weld Type | Common Use |
|---|---|---|
| Triangle (right angle on left) | Fillet weld | Lap joints, T-joints, corner joints |
| V shape | V-groove weld | Butt joints, edge-to-edge |
| Half V (one straight side) | Bevel groove weld | Butt joints where only one edge is chamfered |
| U shape | U-groove weld | Thick sections needing full penetration |
| Rectangle | Plug or slot weld | Joining overlapping plates through holes |
| Straight line across reference | Square groove | Tight-fit butt joints with no edge prep |
Fillet Weld Symbols
The fillet weld is the most common symbol you will encounter. It looks like a right triangle on the reference line with the perpendicular leg always on the left.
- Leg size appears to the left of the symbol
- Weld length appears to the right
- Intermittent welds show length and pitch separated by a dash
Groove Weld Symbols
Groove welds join edges together. The symbol shape matches the groove profile. A V-groove looks like a V; a bevel looks like half a V. The groove angle and root opening are noted on the symbol. For bevel and J-groove welds, the arrow points to the piece that gets the edge preparation.
Supplementary Symbols You Should Know
With AWS welding symbols explained in the full standard (ANSI/AWS A2.4), several supplementary marks modify the basic weld instruction:
- Flag at the arrow/reference line junction: field weld, done on-site during erection
- Open circle at the junction: weld goes all the way around the joint
- Contour symbols (flat, convex, concave): finished shape of the weld surface
- Melt-thru (filled half-circle opposite the weld): full penetration with back-side reinforcement
These marks change what you do after the weld is laid. A flush contour means you grind smooth. A flag tells you the joint stays open until assembly on-site. Any AWS welding symbols explained reference will cover these in detail.
Reading Size, Length, and Process
Here is where to find critical dimensions on any welding symbol, with AWS welding symbols explained in table form:
| Information | Where to Find It |
|---|---|
| Weld type | Symbol shape on or near reference line |
| Weld size (leg or throat) | Left of the symbol |
| Weld length | Right of the symbol |
| Pitch (spacing for intermittent welds) | Right of the symbol, after a dash |
| Groove angle | Inside or beside the groove symbol |
| Root opening | Inside the groove symbol |
| Welding process (MIG, TIG, stick) | In the tail |
| Special instructions | In the tail |
If the tail is empty, it usually means the welding process is either specified elsewhere on the drawing or left to the welder’s judgment based on the shop’s standard procedures.
Weld Symbol vs. Welding Symbol
A weld symbol is the single icon representing the weld type (triangle for fillet, V for groove). A welding symbol is the complete instruction set: reference line, arrow, weld symbol, dimensions, tail, and supplementary marks together. The weld symbol meaning blueprint readers need is just one piece of the larger welding symbol.
Where to Find a Complete Welding Symbol Chart
The definitive reference is ANSI/AWS A2.4 from the American Welding Society. Lincoln Electric and other equipment manufacturers publish free downloadable charts. Print a welding symbol chart and post it near your welding station for quick reference on prints you do not see every day. Having a welding symbol chart visible saves time, especially on jobs with groove or supplementary symbols you do not run regularly.
Getting Set Up to Weld What the Print Calls For
This welding drawing symbols guide covers the basics, but execution requires the right equipment. CryoWeld carries MIG and TIG machines, torches and accessories, welding wire and filler rod, shielding gas, and safety gear from Lincoln Electric, Tweco, Weldcraft, and Jackson Safety.
If the print calls for a process or filler metal you have not run before, now you know how to read welding symbols for what is needed. Stop by our Poughkeepsie or Lake Katrine location in the Hudson Valley. Call Poughkeepsie at (845) 473-3357 or Lake Katrine at (845) 336-8680, weekdays 8 to 5. Or visit cryoweld.com.
FAQs
What do welding symbols on a blueprint mean?
Welding symbols are shorthand instructions that tell the welder what type of weld to make, where to place it, how big it should be, and what process to use. Understanding the meaning of weld symbols in blueprint drawings requires knowing the reference line, arrow, and symbol structure defined in AWS A2.4.
How do you read a fillet weld symbol?
The fillet symbol is a right triangle on the reference line with the perpendicular leg on the left. Leg size is noted to the left of the symbol, weld length to the right. If it is below the reference line, weld on the arrow side. Above the line means the other side.
What is the difference between a weld symbol and a welding symbol?
A weld symbol is the single icon representing the weld type (triangle for fillet, V for groove). A welding symbol is the complete instruction set: reference line, arrow, weld symbol, dimensions, tail, and any supplementary marks. Any welding drawing symbols guide will explain both.
Where can I find a complete welding symbol chart?
The official source is ANSI/AWS A2.4 from the American Welding Society. Lincoln Electric and other manufacturers publish free downloadable charts. Print one and keep it at your welding station for quick reference.
What does the flag on a welding symbol mean?
A flag at the junction of the arrow and reference line indicates a field weld. It means the joint should be welded during on-site erection of the structure, not in the shop during fabrication. Older drawings may use a filled black circle instead of a flag.