GaugePass

Weld symbol

Unequal leg fillet weld symbol

Two numbers separated by a multiplication sign to the left of the fillet triangle call for legs of different lengths, and the drawing has to show which leg goes on which member.

Interactive drawing

1/4 x 1/2
TitleUnequal leg fillet symbol
ViewAs drawn
Sheet1 / 2
The symbol as it appears on the drawing
arrowarrow sideother side
TitleUnequal leg fillet joint
ViewSection
Sheet2 / 2
The joint it produces, in cross-section

Reads asArrow side: fillet weld, 1/4 by 1/2 size.

How to read it

Most fillets are dimensioned with one number because both legs are the same. When the design wants a long, shallow weld or a tall, narrow one, two sizes appear to the left of the triangle in the form of one dimension by another. The pair is a description of the triangle's two legs, so a 1/4 by 1/2 fillet has a quarter-inch leg on one member and a half-inch leg on the other.

The notation itself cannot say which leg goes where, because the triangle is always drawn the same way regardless of joint orientation. That information comes from the drawing: a detail view, a dimension on the joint sketch, or a note beside the symbol. Never assume the first number belongs to the vertical member - check the detail, because getting it backwards changes the weld's throat orientation and its behaviour under load.

Unequal legs show up where the two members differ in thickness, where a long leg is wanted to spread load onto a thin plate, or where a taller leg is needed to reach past a radius or a fit-up gap. They also appear in fatigue-sensitive details, since a shallower approach angle at the toe eases the stress concentration where the weld meets the base metal.

Everything else on the symbol reads normally. A length to the right still sets the run, a length-pitch pair still makes it intermittent, and a triangle on each side still means both faces get welded. When both faces carry unequal legs, each side gets its own pair of numbers and each has to be checked against its own detail view.

Where each dimension goes

First size
One leg of the fillet triangle, in the units of the drawing.
Second size
The other leg. The pair describes the two sides of the triangle, not a range.
Detail view or note
Where the orientation lives - which member carries the long leg. The symbol alone cannot say.
Length and pitch (right of the triangle)
Run length and centre-to-centre spacing, exactly as on an equal-leg fillet.

Worked examples

Each one is a drawing, the sentence it comes out as, and then the mark-by-mark account of why. Read the sheet first and say the sentence yourself before you look down.

  1. Long leg along the base plate

    5/16 x 3/4
    TitleLong leg along the base plate
    RefUnequal leg fillet
    Ex1 / 2

    Reads as

    Weld a fillet with a 5/16 leg on the upright and a 3/4 leg along the plate.

    Which mark says so

    • fillet symbolBelow the reference lineA fillet weld on the arrow side of the joint
    • 5/16 × 3/4Left of the symbolTwo unequal legs, the first measured along the member the arrow touches

    The two numbers left of the triangle give the two legs. Which member gets the 3/4 comes from the detail view beside the symbol, not from the order of the numbers.

    And what it does not say

    • No length is given, so each weld runs the full length of the joint.
    • Nothing sits above the reference line, so the far face of the joint stays bare.
    • There is no circle at the elbow, so the weld does not continue around the joint.

  2. Unequal legs on both faces

    1/41/4 x 1/2
    TitleUnequal legs on both faces
    RefUnequal leg fillet
    Ex2 / 2

    Reads as

    Put a 1/4 by 1/2 fillet on the arrow side and an equal 1/4 fillet opposite.

    Which mark says so

    • fillet symbolBelow the reference lineA fillet weld on the arrow side of the joint
    • 1/4 × 1/2Left of the arrow-side symbolTwo unequal legs, the first measured along the member the arrow touches
    • fillet symbolAbove the reference lineA fillet weld on the far side of the joint
    • 1/4Left of the other-side symbolLeg size of the fillet

    The lower triangle carries a pair of sizes and the upper carries a single size, so one face gets an unequal-leg weld and the other a conventional symmetric one.

    And what it does not say

    • No length is given, so each weld runs the full length of the joint.
    • There is no circle at the elbow, so the weld does not continue around the joint.

Common mistakes

  • Assuming the first number always belongs to the vertical member without checking the detail view.
  • Reading the two sizes as a tolerance range rather than as two legs of the same weld.
  • Measuring only one leg during inspection and passing the weld when the other is short.
  • Copying the pair onto the opposite face when that face carries its own, different callout.

Typical joints

Thick-to-thin plate teesLap joints where load is spread along one memberStiffener attachments over a fillet radiusFatigue-sensitive toe details

Related symbols

Fillet weldThe right triangle on the reference line calls for a fillet weld. The number to its left is the leg size, and the side of the line it sits on tells you which face of the joint gets welded.Double filletA fillet triangle above and below the reference line means both faces of the same joint get welded. Each triangle carries its own size and length, so the two welds do not have to match.Intermittent filletTwo 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.Reference line basicsEvery welding symbol is built on one horizontal reference line with an arrow at one end and an optional tail at the other. Where information sits on that line is what gives it meaning.