Weld symbol
Intermittent fillet weld symbol
Two numbers to the right of the fillet triangle turn a continuous weld into a series of segments: the first is how long each segment runs, the second is the centre-to-centre spacing between them.
Reads as: Arrow side: fillet weld, 3/16 size, 2 long, 6 pitch.
How to read it
An intermittent fillet looks exactly like an ordinary fillet symbol until you reach the right-hand side of the triangle. There you find a pair of numbers separated by a dash. The first is the length of each individual weld segment. The second is the pitch, and pitch is measured centre to centre, from the middle of one segment to the middle of the next — not from the end of one to the start of the next.
That distinction is where money and metal get lost. With a 2-5 callout, each weld is two inches long and the next weld starts five inches after the previous one started, which leaves three inches of unwelded joint between segments. Read pitch as a gap instead of a centre distance and you will lay down welds five inches apart edge to edge, putting far less weld on the part than the designer asked for.
Everything else about the fillet symbol carries over unchanged. The number left of the triangle is still the leg size, the side of the reference line still says which face of the joint gets the welds, and a triangle on each side means both faces get an intermittent pattern. If the two sides carry different length-pitch numbers, they are independent instructions and each is read on its own.
Segments are normally started and stopped inside the joint, not wrapped around ends, unless a circle at the elbow calls for welding all around. Where the drawing needs the pattern to begin or end at a particular feature, that intent is usually spelled out in a note next to the symbol rather than encoded in the numbers, so read any adjacent note before laying out your marks.
Where each dimension goes
- Size (left of the triangle)
- Leg length of each fillet segment. All segments in the run share this size.
- Length (first number on the right)
- How long one individual weld segment runs along the joint.
- Pitch (second number on the right)
- Centre-to-centre distance from one segment to the next, so the clear gap is pitch minus length.
- Side of the reference line
- Which face of the joint carries the intermittent pattern. Each side is dimensioned independently.
Worked examples
Two-inch welds on a five-inch pitch
“Lay 1/4 fillets two inches long, spaced five inches centre to centre, on the arrow side.”
The 1/4 left of the triangle is the leg. The 2 is the segment length and the 5 is the pitch, so each weld is followed by three inches of bare joint before the next one begins.
Matched intermittent welds on both faces
“Run 3/16 fillets three inches long on eight-inch centres on both sides of the joint.”
Both sides carry the same triangle and the same 3-8 length-pitch pair, so the two faces get identical patterns. Because they are not offset, the segments line up across the joint.
Common mistakes
- Reading the pitch as the clear gap between segments instead of a centre-to-centre distance.
- Adding the length and the pitch together when laying out marks, which doubles the spacing.
- Assuming an intermittent pattern on one side automatically mirrors onto the other side.
- Skipping the end segments so the weld pattern stops short of the joint ends without a note allowing it.
Typical joints
Related symbols
Practise reading welds, not just symbols
The drawing tells you what the weld should be. The gauge trainer is where you find out whether you can tell what it actually is.