This cheat sheet explains how to read the side and arrow significance of welding symbols used on engineering drawings. Students need it because weld location is communicated by symbol placement, not by long written directions. Correctly reading arrow side, other side, and both sides helps prevent fabrication errors.
It is especially useful when moving from classroom sketching to industry-style print reading.
The main rule is that a weld symbol below the reference line means the weld goes on the arrow side of the joint. A weld symbol above the reference line means the weld goes on the other side of the joint. Matching symbols on both sides of the reference line mean weld both sides.
The arrow points to the joint, while the tail is used for process, specification, or other notes when needed.
Key Facts
- The reference line is the horizontal line where weld symbols are placed to show weld type and side.
- A weld symbol below the reference line means the weld is on the arrow side of the joint.
- A weld symbol above the reference line means the weld is on the other side of the joint.
- The arrow side is the side of the joint that the arrow physically points toward on the drawing.
- The other side is the side of the joint opposite the side indicated by the arrow.
- A weld symbol shown both above and below the reference line means the weld is required on both sides of the joint.
- The tail may contain welding process notes such as GMAW, SMAW, or a required welding specification.
- If no tail information is needed, the tail may be omitted from the welding symbol.
Vocabulary
- Welding symbol
- A complete drawing symbol that gives weld location, weld type, size, length, process, and other required information.
- Weld symbol
- The small graphic shape on the reference line that identifies the type of weld, such as a fillet weld or groove weld.
- Reference line
- The horizontal line in a welding symbol that organizes the weld symbol, dimensions, and notes.
- Arrow side
- The side of the joint to which the arrow points, where weld symbols below the reference line apply.
- Other side
- The side of the joint opposite the arrow side, where weld symbols above the reference line apply.
- Tail
- The optional forked end of a welding symbol that lists the welding process, specification, or special instructions.
Common Mistakes to Avoid
- Reading the arrow as a weld direction, which is wrong because the arrow identifies the joint location and arrow side, not the travel direction of welding.
- Putting an arrow-side weld symbol above the reference line, which is wrong because symbols above the line apply to the other side of the joint.
- Assuming both sides are welded when only one symbol is shown, which is wrong because both-side welding requires symbols above and below the reference line or a clear note.
- Ignoring the tail note, which is wrong because it may specify the required welding process, code, or procedure.
- Confusing the weld symbol with the full welding symbol, which is wrong because the full welding symbol includes the reference line, arrow, tail, dimensions, and notes.
Practice Questions
- 1 A fillet weld symbol is placed below the reference line, and the arrow points to the front plate of a T-joint. Which side gets the weld?
- 2 A welding symbol shows a groove weld symbol above the reference line only. If the arrow points to Side A, which side is welded?
- 3 A fillet weld symbol is shown both above and below the reference line, and the tail says GMAW. What weld location and welding process are required?
- 4 Explain why placing a weld symbol above or below the reference line is more precise than writing only weld this joint on an engineering drawing.