{ "slug": "welding-symbols", "title": "Welding Symbols: ISO 2553 vs AWS A2.4 Compared", "description": "All 22 weld symbols compared across ISO 2553 System A/B and AWS A2.4, with arrow-side rules, a/z throat conversions and intermittent-weld counting examples.", "lang": "en", "tables": [ { "caption": "Weld symbols compared: ISO 2553 (2019) vs AWS A2.4 (2020), 22 types", "columns": [ "No.", "Weld type", "Symbol form (text description)", "ISO 2553 (A / B)", "AWS A2.4", "Arrow side / other side", "Dimension notation (ISO → AWS)", "Typical application", "Common misreading", "Source" ], "rows": [ { "No.": "1", "Weld type": "Fillet weld", "Symbol form (text description)": "right triangle, legs on the reference line, hypotenuse outward", "ISO 2553 (A / B)": "Table 1 No.10; clause 5.5 — A: solid line = arrow side, dashed = other side; B: below = arrow side", "AWS A2.4": "§8; triangle; bare number on the left", "Arrow side / other side": "A vs B/AWS directions are opposite; mirrored when welded both sides", "Dimension notation (ISO → AWS)": "ISO a (throat) or z (leg) left, length right → AWS bare number = leg left, length-pitch right", "Typical application": "T, lap and corner joints — the everyday weld", "Common misreading": "reading a as a leg, or reading up/down in System A", "Source": "S1, S5, S6, S8" }, { "No.": "2", "Weld type": "Square / I butt weld", "Symbol form (text description)": "two short parallel vertical lines, no preparation", "ISO 2553 (A / B)": "Table 1 No.1; clause 5.4", "AWS A2.4": "§7 square groove; two parallel lines", "Arrow side / other side": "groove rules; one symbol for single-side welds", "Dimension notation (ISO → AWS)": "ISO s = penetration; no size = full penetration → AWS D(S) + R (root opening)", "Typical application": "thin sheet, low current, single side", "Common misreading": "assuming no size means anything goes — ISO defaults to full penetration", "Source": "S1, S11, S6" }, { "No.": "3", "Weld type": "Single-V groove", "Symbol form (text description)": "symmetrical V opening, apex on the line", "ISO 2553 (A / B)": "Table 1 No.2; clause 5.4", "AWS A2.4": "§7 V-groove", "Arrow side / other side": "single-side preparation on one member; double side = X", "Dimension notation (ISO → AWS)": "ISO s penetration, α on the symbol → AWS D(S), R, α", "Typical application": "medium plate, single-side full penetration", "Common misreading": "reading s as preparation depth, or the root gap as penetration", "Source": "S1, S6, S7" }, { "No.": "4", "Weld type": "V with root face (Y)", "Symbol form (text description)": "V with a short flat land at the bottom — reads like a Y", "ISO 2553 (A / B)": "Table 1 No.3; clause 5.4", "AWS A2.4": "no separate symbol — V plus root-face note", "Arrow side / other side": "same as V", "Dimension notation (ISO → AWS)": "ISO s + root face depth (letter: declared gap) → AWS D(S) + note", "Typical application": "burn-through control, thick plate, single side", "Common misreading": "treating it as a plain V and losing the root face", "Source": "S1, S11, S6" }, { "No.": "5", "Weld type": "Double-V (X)", "Symbol form (text description)": "two V shapes sharing the root, forming an X", "ISO 2553 (A / B)": "Table 2 combination No.1; symmetric double-sided may omit the dashed line", "AWS A2.4": "§7 double-V", "Arrow side / other side": "symmetric — no arrow/other-side meaning", "Dimension notation (ISO → AWS)": "ISO s per side (no total) → AWS D(S) per side + α", "Typical application": "thick plate, both sides accessible, distortion control", "Common misreading": "adding the two sides' penetrations into a total", "Source": "S1, S11, S6" }, { "No.": "6", "Weld type": "Single-bevel groove", "Symbol form (text description)": "half a V: one vertical edge + one inclined edge", "ISO 2553 (A / B)": "Table 1 No.4; clause 5.3 — arrow points at the prepared member", "AWS A2.4": "§7 bevel; §6.4 broken arrow points at the prepared member", "Arrow side / other side": "ISO arrow marks the prepared plate; AWS uses the broken arrow", "Dimension notation (ISO → AWS)": "ISO s + bevel angle β → AWS D(S), R, α", "Typical application": "T-joints, preparation possible on one member only", "Common misreading": "arrow on the wrong plate — the bevel ends up on the unprepared one", "Source": "S1, S2, S6" }, { "No.": "7", "Weld type": "Double-bevel (K)", "Symbol form (text description)": "two half-Vs back to back, forming a K", "ISO 2553 (A / B)": "Table 2 combination No.2; symmetric", "AWS A2.4": "§7 double-bevel", "Arrow side / other side": "symmetric, no side meaning", "Dimension notation (ISO → AWS)": "one set per side", "Typical application": "thick T-joints, both sides accessible", "Common misreading": "confusing K with X; reading the bevel directions backwards", "Source": "S1, S11, S6" }, { "No.": "8", "Weld type": "Single-U groove", "Symbol form (text description)": "U shape: rounded bottom + two vertical sides, usually with a root face", "ISO 2553 (A / B)": "Table 1 No.6; clause 5.4", "AWS A2.4": "§7 U-groove", "Arrow side / other side": "same as V", "Dimension notation (ISO → AWS)": "ISO s, R (root radius), root face → AWS D(S), R, α", "Typical application": "thick plate, narrow preparation, filler savings", "Common misreading": "confusing with J (J has one rounded side only)", "Source": "S1, S6, S13" }, { "No.": "9", "Weld type": "Double-U", "Symbol form (text description)": "two U shapes stacked", "ISO 2553 (A / B)": "Table 2 combination No.5; symmetric", "AWS A2.4": "§7 double-U", "Arrow side / other side": "symmetric, no side meaning", "Dimension notation (ISO → AWS)": "one set per side", "Typical application": "very thick plate", "Common misreading": "treating as double-V; losing the root radii", "Source": "S1, S11, S6" }, { "No.": "10", "Weld type": "Single-J groove", "Symbol form (text description)": "half a U: one vertical side + one rounded side", "ISO 2553 (A / B)": "Table 1 No.7; clause 5.3 — arrow points at the prepared member", "AWS A2.4": "§7 J-groove; broken arrow", "Arrow side / other side": "ISO arrow marks the prepared side; AWS broken arrow", "Dimension notation (ISO → AWS)": "ISO s, R, root face → AWS D(S), R", "Typical application": "thick plate single-side, nozzles and tubes", "Common misreading": "confusing with single-U; arrow on the wrong side", "Source": "S1, S2, S6" }, { "No.": "11", "Weld type": "Double-J", "Symbol form (text description)": "two J shapes stacked", "ISO 2553 (A / B)": "Table 2 combination (J both directions); symmetric", "AWS A2.4": "§7 double-J", "Arrow side / other side": "symmetric, no side meaning", "Dimension notation (ISO → AWS)": "one set per side", "Typical application": "very thick plate, both sides accessible", "Common misreading": "direction read backwards", "Source": "S1, S11, S6" }, { "No.": "12", "Weld type": "Flare-V groove", "Symbol form (text description)": "two outward-flaring arcs forming a wide-mouth V", "ISO 2553 (A / B)": "Table 1 No.8", "AWS A2.4": "§7 flare-V", "Arrow side / other side": "groove rules; arrow at the joint", "Dimension notation (ISO → AWS)": "ISO s → AWS effective throat from the radius via the D1.1 prequalified table (coefficient varies by edition)", "Typical application": "tube or rounded profile butt-welded to plate", "Common misreading": "using the 0.707 fillet factor — overstates the throat", "Source": "S1, S6, S15" }, { "No.": "13", "Weld type": "Flare-bevel groove", "Symbol form (text description)": "one flaring arc + one straight edge — half a flare mouth", "ISO 2553 (A / B)": "Table 1 No.9", "AWS A2.4": "§7 flare-bevel", "Arrow side / other side": "bevel rules; arrow at the joint", "Dimension notation (ISO → AWS)": "ISO s → AWS coefficient from R and process, see the flare-bevel question (§ Q13)", "Typical application": "tube onto plate, rounded-to-flat joints", "Common misreading": "computing the throat with plain-bevel geometry", "Source": "S1, S6, S15" }, { "No.": "14", "Weld type": "Plug weld (round hole)", "Symbol form (text description)": "rectangle representing the hole, filled with weld", "ISO 2553 (A / B)": "Table 1 No.11; clause 5.6", "AWS A2.4": "§9 plug weld; rectangle", "Arrow side / other side": "arrow points at the drilled member", "Dimension notation (ISO → AWS)": "ISO d hole dia left, fill depth inside (omit = fill flush) → AWS dia (Ø still used for the size), depth inside, pitch right, count in brackets", "Typical application": "lap joints, one side accessible, closed structures", "Common misreading": "reading the hole diameter as a leg size", "Source": "S1, S11, S7" }, { "No.": "15", "Weld type": "Slot weld", "Symbol form (text description)": "elongated rectangle, filled with weld", "ISO 2553 (A / B)": "Table 1 No.11; clause 5.7", "AWS A2.4": "§10 slot weld; rectangle", "Arrow side / other side": "arrow points at the slotted member", "Dimension notation (ISO → AWS)": "ISO width c left, fill depth inside → AWS width + length left, depth inside, pitch right, count in brackets", "Typical application": "long slots, reinforcement connections", "Common misreading": "swapping slot width and length", "Source": "S1, S11, S7" }, { "No.": "16", "Weld type": "Spot weld (resistance or arc)", "Symbol form (text description)": "hollow circle centred on the reference line", "ISO 2553 (A / B)": "Table 1 No.12 (resistance) / No.13 (arc); clause 5.8", "AWS A2.4": "§11 spot weld; hollow circle", "Arrow side / other side": "symmetric — no arrow/other-side meaning", "Dimension notation (ISO → AWS)": "ISO d nugget dia left, n × (e) right → AWS size left (2020: size only, no strength), pitch right, count in brackets", "Typical application": "thin sheet laps: automotive, appliances", "Common misreading": "reading d as a leg; reading e as a centre distance", "Source": "S1, S11, S6, S12" }, { "No.": "17", "Weld type": "Seam weld (resistance or arc)", "Symbol form (text description)": "ISO: rectangle with a centre line; AWS: circle with two parallel lines", "ISO 2553 (A / B)": "Table 1 No.14 / No.15; clause 5.9", "AWS A2.4": "§12 seam weld", "Arrow side / other side": "no side meaning", "Dimension notation (ISO → AWS)": "ISO width c left; intermittent n × l (e) right → AWS size left, length-pitch right", "Typical application": "sealed seams: tanks, ducting, tubes", "Common misreading": "continuous vs intermittent swapped; width read as depth", "Source": "S1, S11, S6, S15" }, { "No.": "18", "Weld type": "Stud weld", "Symbol form (text description)": "ISO: dedicated stud symbol (official graphic unverified — declared gap); AWS: circle with an X", "ISO 2553 (A / B)": "Table 1 No.16; clause 5.11", "AWS A2.4": "§14 stud weld; circle-X", "Arrow side / other side": "arrow side only — no other-side usage", "Dimension notation (ISO → AWS)": "ISO d stud dia left, n × (e) right → AWS size left, pitch right, count below in brackets", "Typical application": "shear studs: construction, bridges, façades", "Common misreading": "treating as a spot weld; dropping count/pitch", "Source": "S1, S11, S6, S15" }, { "No.": "19", "Weld type": "Edge weld", "Symbol form (text description)": "ISO: three short parallel vertical lines; AWS: three short legs under a cap", "ISO 2553 (A / B)": "Table 1 No.19; clause 5.10", "AWS A2.4": "§13 edge weld — different shape from the ISO form", "Arrow side / other side": "one side; arrow at the edge", "Dimension notation (ISO → AWS)": "ISO plate thickness left → AWS size/thickness note", "Typical application": "thin sheet edges: flanges, closed borders", "Common misreading": "confusing with flanged welds; cross-reading the two shapes", "Source": "S1, S11, S13, S6, S15" }, { "No.": "20", "Weld type": "Flanged butt / corner weld", "Symbol form (text description)": "two outward-flaring lines (an open eight), edge fully melted", "ISO 2553 (A / B)": "Table 1 No.20", "AWS A2.4": "§13 edge weld covers flanged butt/corner", "Arrow side / other side": "one side; arrow at the flange", "Dimension notation (ISO → AWS)": "ISO plate/flange size → AWS size note", "Typical application": "thin sheet: appliances, vessels, ducting", "Common misreading": "treating as a V preparation; missing the full-fusion requirement", "Source": "S1, S13, S6" }, { "No.": "21", "Weld type": "Surfacing / build-up", "Symbol form (text description)": "wavy line along the reference line", "ISO 2553 (A / B)": "Table 1 No.21; clause 5.12", "AWS A2.4": "§15 surfacing; wavy line", "Arrow side / other side": "no side meaning", "Dimension notation (ISO → AWS)": "ISO layer size per clause 5.12 → AWS size left", "Typical application": "wear layers, repair, cladding", "Common misreading": "mistaking for a seam weld", "Source": "S1, S11, S6, S15" }, { "No.": "22", "Weld type": "Backing run / back weld (and backing strips)", "Symbol form (text description)": "open half-circle supplementary symbol on the far side; distinguish from backing-strip symbols; AWS melt-through is a filled half-circle", "ISO 2553 (A / B)": "Table 3 No.5 (backing run); No.7a–7c (backing strips)", "AWS A2.4": "§7.7 backing / back weld", "Arrow side / other side": "far-side half-circle = weld-from-the-back; multiple reference lines sequence the operations", "Dimension notation (ISO → AWS)": "no size; process/sequence in the tail or on additional reference lines", "Typical application": "single-side full-penetration joints with a sealed root", "Common misreading": "confusing the backing strip (a part) with the backing run (a weld)", "Source": "S1, S11, S6, S15" } ] }, { "caption": "In AWS A2.4, is a weld symbol above the reference line on the arrow side or the other side?", "columns": [ "System", "Reference line", "Arrow side", "Other side", "Symmetric double-sided" ], "rows": [ { "System": "ISO 2553 System A", "Reference line": "solid line + dashed identification line (dashed may be above or below)", "Arrow side": "symbol on the SOLID line (either up or down)", "Other side": "symbol on the DASHED line", "Symmetric double-sided": "one symbol each; symmetric pairs may omit the dashed line" }, { "System": "ISO 2553 System B", "Reference line": "single solid line", "Arrow side": "symbol BELOW the line", "Other side": "symbol ABOVE the line", "Symmetric double-sided": "one symbol each side" }, { "System": "AWS A2.4", "Reference line": "single solid line (always horizontal)", "Arrow side": "symbol BELOW the line (§6.1)", "Other side": "symbol ABOVE the line (§6.1)", "Symmetric double-sided": "one symbol each; staggered by offsetting, no Z mark" } ] }, { "caption": "How much throat thickness is lost if an ISO a6 fillet is fabricated as a 6 mm leg?", "columns": [ "Step", "Item", "Basis", "Value" ], "rows": [ { "Step": "1", "Item": "Leg required for a6", "Basis": "z = a × √2", "Value": "6 × 1.4142 = 8.485 mm" }, { "Step": "2", "Item": "Throat actually built at z6", "Basis": "a = z / √2", "Value": "6 / 1.4142 = 4.243 mm (−29.3%)" }, { "Step": "3", "Item": "Section area required / actual", "Basis": "A = a² / A = z²/2", "Value": "36.0 vs 18.0 mm² (−50%)" }, { "Step": "4", "Item": "Metal over 8 m of weld", "Basis": "V = A × 8,000 mm", "Value": "288 vs 144 cm³ — a 144 cm³ shortfall" }, { "Step": "5", "Item": "Moral", "Basis": "—", "Value": "z = a√2, A = z²/2, V = A×L — three lines catch the whole error" } ] }, { "caption": "What leg length satisfies an ISO a5 throat?", "columns": [ "Drawing callout", "Converts to", "Note" ], "rows": [ { "Drawing callout": "a4", "Converts to": "z ≈ 5.7 mm", "Note": "z = a × 1.414" }, { "Drawing callout": "a5", "Converts to": "z ≈ 7.07 mm", "Note": "z7 = 4.95 mm throat (1% under); z8 = 5.66 mm (13% over)" }, { "Drawing callout": "a6", "Converts to": "z ≈ 8.49 mm", "Note": "the worked example above" }, { "Drawing callout": "z6", "Converts to": "a ≈ 4.24 mm", "Note": "a = z / 1.414" }, { "Drawing callout": "z8", "Converts to": "a ≈ 5.66 mm", "Note": "if the buyer wants an 8 mm throat they must write a8 (leg ≈ 11.3 mm)" }, { "Drawing callout": "AWS bare 6", "Converts to": "leg = 6 mm, throat ≈ 4.24 mm", "Note": "AWS numbers are legs already — do not divide again" } ] }, { "caption": "What does AWS 12(10) mean on a groove weld?", "columns": [ "AWS edition", "Notation", "Meaning" ], "rows": [ { "AWS edition": "A2.4:2012 and later (incl. 2020)", "Notation": "D(S) — D = groove depth, (S) = weld size / effective throat", "Meaning": "12(10) = 12 mm deep, 10 mm effective throat" }, { "AWS edition": "Before A2.4:2012", "Notation": "S(E) — S = depth placeholder, (E) = effective throat", "Meaning": "same physical meaning, different letters — do not read an old drawing with the new rules" } ] }, { "caption": "How many weld elements does AWS 75-150 produce on a 6000 mm beam?", "columns": [ "Step", "Item", "Value" ], "rows": [ { "Step": "1", "Item": "Count (pitch = centre-to-centre)", "Value": "n = floor((6000 − 75) / 150) + 1 = 40 per side" }, { "Step": "2", "Item": "Weld length per side", "Value": "40 × 75 = 3000 mm" }, { "Step": "3", "Item": "Fillet metal", "Value": "A = z²/2 = 18.0 mm²; 3000 × 18.0 = 54.0 cm³ per side; 108.0 cm³ both sides" }, { "Step": "4", "Item": "ISO equivalent notation", "Value": "e = 150 − 75 = 75 → n × l (e) = 40 × 75 (75)" } ] }, { "caption": "If 150 is misread as ISO edge-to-edge e, how many elements result?", "columns": [ "Item", "ISO n × l (e)", "AWS length-pitch" ], "rows": [ { "Item": "Position", "ISO n × l (e)": "right of the symbol", "AWS length-pitch": "right of the symbol" }, { "Item": "Count", "ISO n × l (e)": "n written explicitly", "AWS length-pitch": "count in brackets / inferred" }, { "Item": "Length", "ISO n × l (e)": "l = length of each element", "AWS length-pitch": "length left of the hyphen" }, { "Item": "Spacing meaning", "ISO n × l (e)": "(e) = clear gap, edge to edge", "AWS length-pitch": "pitch = centre to centre" }, { "Item": "Conversion", "ISO n × l (e)": "pitch = l + e; e = pitch − l", "AWS length-pitch": "same relation, other side of the equation" }, { "Item": "Staggered elements", "ISO n × l (e)": "Z mark on the reference line", "AWS length-pitch": "offset symbols above/below, no Z" }, { "Item": "The 75-150 case", "ISO n × l (e)": "misread as e: period 225 mm → 27 elements, 2025 mm (−32.5%)", "AWS length-pitch": "pitch 150 → 40 elements, 3000 mm" } ] }, { "caption": "What is the minimum AWS D1.1 fillet leg for 10 mm plate?", "columns": [ "Base metal thickness T", "Minimum leg (in)", "Minimum leg (mm)", "Note" ], "rows": [ { "Base metal thickness T": "T ≤ 1/4 in (≤ 6 mm)", "Minimum leg (in)": "1/8 in", "Minimum leg (mm)": "3 mm", "Note": "cyclically loaded structures take 3/16 in (5 mm)" }, { "Base metal thickness T": "1/4 in < T ≤ 1/2 in (6–12 mm)", "Minimum leg (in)": "3/16 in", "Minimum leg (mm)": "5 mm", "Note": "rounded value; D1.1 tabulates inches (4.76 mm exact)" }, { "Base metal thickness T": "1/2 in < T ≤ 3/4 in (12–20 mm)", "Minimum leg (in)": "1/4 in", "Minimum leg (mm)": "6 mm", "Note": "" }, { "Base metal thickness T": "T > 3/4 in (> 20 mm)", "Minimum leg (in)": "5/16 in", "Minimum leg (mm)": "8 mm", "Note": "" } ] }, { "caption": "What is the minimum AWS D1.1 fillet leg for 25 mm plate?", "columns": [ "Base metal thickness T", "Minimum leg (in)", "Minimum leg (mm)" ], "rows": [ { "Base metal thickness T": "T > 3/4 in (> 20 mm) — covers 25 mm plate", "Minimum leg (in)": "5/16 in", "Minimum leg (mm)": "8 mm" }, { "Base metal thickness T": "1/2 in < T ≤ 3/4 in (12–20 mm)", "Minimum leg (in)": "1/4 in", "Minimum leg (mm)": "6 mm" } ] }, { "caption": "How wide is a 60° V groove at 12 mm depth with a 2 mm root gap?", "columns": [ "Step", "Item", "Value" ], "rows": [ { "Step": "1", "Item": "Inputs (declared)", "Value": "angle 60°, depth 12 mm, root gap 2 mm" }, { "Step": "2", "Item": "Top width", "Value": "2 × 12 × tan 30° + 2 = 13.86 + 2 = 15.86 mm" }, { "Step": "3", "Item": "Cross-section area (trapezoid)", "Value": "12 × (15.86 + 2) / 2 = 107.1 mm²" }, { "Step": "4", "Item": "Filler per metre", "Value": "107.1 mm² × 1000 mm = 107.1 cm³/m" } ] }, { "caption": "Does an undimensioned ISO butt weld mean partial penetration?", "columns": [ "System", "Default reading", "Source" ], "rows": [ { "System": "ISO 2553", "Default reading": "no size on a butt weld and no other note → full penetration assumed", "Source": "S1, S11" }, { "System": "AWS A2.4", "Default reading": "no blank-space defaults — CJP by note/symbol, PJP by D(S)", "Source": "S7" } ] }, { "caption": "Can ISO System A and System B be mixed on one drawing?", "columns": [ "Step", "Evidence on the drawing", "Verdict", "Risk if ignored" ], "rows": [ { "Step": "1", "Evidence on the drawing": "solid reference line AND a parallel dashed line, symbols on both", "Verdict": "ISO System A — line type decides the side, never up/down", "Risk if ignored": "reading up/down flips every weld to the wrong face" }, { "Step": "2", "Evidence on the drawing": "single line, title block says ISO 2553 System B", "Verdict": "below = arrow side, above = other side; size letters still ISO (a/z/e)", "Risk if ignored": "same side rule as AWS but different letters" }, { "Step": "3", "Evidence on the drawing": "single line, title block says AWS A2.4", "Verdict": "below = arrow side; bare numbers are legs", "Risk if ignored": "reading a bare leg as an ISO throat undersizes welds" }, { "Step": "4", "Evidence on the drawing": "single line, no standard declared", "Verdict": "unresolved — send an RFI: standard + system + units", "Risk if ignored": "guessing wrong flips a whole batch" }, { "Step": "5", "Evidence on the drawing": "drawing says ISO 2553 but neither A nor B", "Verdict": "non-conforming — ask the customer to add A or B", "Risk if ignored": "ISO forbids mixing A and B (S1)" }, { "Step": "6", "Evidence on the drawing": "Ø on a plug/spot symbol", "Verdict": "pre-2020 AWS habit or non-AWS practice — 2020 removed Ø from the symbol but sizes still use Ø", "Risk if ignored": "reading an old drawing as 2020" } ] }, { "caption": "How many spot welds at 50 mm pitch over 1 m?", "columns": [ "Item", "Value" ], "rows": [ { "Item": "Intervals in 1000 mm at 50 mm pitch", "Value": "20" }, { "Item": "Spots (both ends welded)", "Value": "20 + 1 = 21" }, { "Item": "Notation", "Value": "AWS pitch 50; ISO equivalent n × (50) with d noted separately" } ] }, { "caption": "What is the AWS effective throat of a flare-bevel weld with R = 12 mm, GMAW?", "columns": [ "Flare joint", "Process", "Effective throat", "At R = 12 mm", "Status" ], "rows": [ { "Flare joint": "Flare-bevel", "Process": "GMAW / FCAW-G", "Effective throat": "5/16 × R", "At R = 12 mm": "3.75 mm", "Status": "D1.1 prequalified effective-throat table (table number varies by edition); source page pending re-verification" }, { "Flare joint": "Flare-V", "Process": "—", "Effective throat": "1/2 R or 3/8 R (per edition)", "At R = 12 mm": "6.0 mm or 4.5 mm", "Status": "verify the coefficient in the edition you buy" }, { "Flare joint": "Flare-bevel — the 5/8 R claim", "Process": "—", "Effective throat": "—", "At R = 12 mm": "—", "Status": "corrected: no D1.1 edition supports 5/8 R for flare-bevel" } ] }, { "caption": "Is a stud weld symbol side-significant?", "columns": [ "Symbol", "Side significance", "Dimension positions" ], "rows": [ { "Symbol": "Stud weld (circle-X)", "Side significance": "arrow side ONLY — no other-side usage", "Dimension positions": "size left, pitch right, count below in brackets" }, { "Symbol": "Spot weld (hollow circle)", "Side significance": "symmetric — no arrow/other-side meaning", "Dimension positions": "size left, pitch right, count in brackets" }, { "Symbol": "Fillet weld (triangle)", "Side significance": "fully side-significant — the most misread symbol on any drawing", "Dimension positions": "size left, length/pitch right" } ] }, { "caption": "What does an empty tail mean in AWS A2.4?", "columns": [ "Tail content", "ISO reading", "AWS reading" ], "rows": [ { "Tail content": "135 / ISO 5817-B / PF", "ISO reading": "process 135 (MAG, ISO 4063) / quality level B / welding position PF", "AWS reading": "not used — AWS tails carry WPS/spec references" }, { "Tail content": "a WPS or spec number", "ISO reading": "possible but unusual — ISO uses 3-digit process numbers", "AWS reading": "the normal use: WPS / specification / reference" }, { "Tail content": "empty", "ISO reading": "no auxiliary requirement stated", "AWS reading": "0 references — no spec applies to this weld as drawn" }, { "Tail content": "basic welding symbol (no joint)", "ISO reading": "tail is REQUIRED — it carries the only information", "AWS reading": "—" } ] }, { "caption": "What do the dimension letters a, z, s, p, R and b mean?", "columns": [ "Letter", "ISO 2553:2019", "AWS A2.4:2020", "GB/T 324-2008 (ISO 1992 line)", "Conflict", "Source" ], "rows": [ { "Letter": "a", "ISO 2553:2019": "nominal throat thickness (fillet)", "AWS A2.4:2020": "not used — bare number = leg", "GB/T 324-2008 (ISO 1992 line)": "not used (S = effective thickness)", "Conflict": "C2", "Source": "S1, S16, S13" }, { "Letter": "z", "ISO 2553:2019": "leg length", "AWS A2.4:2020": "not used", "GB/T 324-2008 (ISO 1992 line)": "not used (K = leg)", "Conflict": "C2", "Source": "S1, S13" }, { "Letter": "s", "ISO 2553:2019": "penetration depth (butt); deep-penetration throat on fillets", "AWS A2.4:2020": "not used", "GB/T 324-2008 (ISO 1992 line)": "not used (H = depth, S = effective thickness)", "Conflict": "C2", "Source": "S1, S16, S3, S13" }, { "Letter": "S", "ISO 2553:2019": "not used", "AWS A2.4:2020": "fillet leg size; in (S) = weld size / effective throat", "GB/T 324-2008 (ISO 1992 line)": "effective throat thickness", "Conflict": "C2, C5", "Source": "S4, S6, S13" }, { "Letter": "D", "ISO 2553:2019": "not used", "AWS A2.4:2020": "groove depth (since 2012)", "GB/T 324-2008 (ISO 1992 line)": "not used (H = depth)", "Conflict": "C5", "Source": "S10, S6" }, { "Letter": "E", "ISO 2553:2019": "not used", "AWS A2.4:2020": "pre-2012 effective throat, written (E)", "GB/T 324-2008 (ISO 1992 line)": "not used", "Conflict": "C5", "Source": "S10" }, { "Letter": "d", "ISO 2553:2019": "diameter: spot / stud / plug", "AWS A2.4:2020": "diameter: spot / plug / stud", "GB/T 324-2008 (ISO 1992 line)": "spot-weld nugget diameter", "Conflict": "—", "Source": "S1, S11, S13" }, { "Letter": "c", "ISO 2553:2019": "seam weld width; slot width", "AWS A2.4:2020": "not used (S / R instead)", "GB/T 324-2008 (ISO 1992 line)": "weld width", "Conflict": "—", "Source": "S1, S11, S13" }, { "Letter": "root face", "ISO 2553:2019": "depth of root face — current letter unverified (declared gap)", "AWS A2.4:2020": "root face by note — no unified letter", "GB/T 324-2008 (ISO 1992 line)": "p (root face)", "Conflict": "C4, G2", "Source": "S1, S6, S13" }, { "Letter": "e", "ISO 2553:2019": "distance between weld elements (clear gap)", "AWS A2.4:2020": "not used (pitch instead)", "GB/T 324-2008 (ISO 1992 line)": "weld spacing", "Conflict": "C3", "Source": "S1, S11, S13" }, { "Letter": "l", "ISO 2553:2019": "length of one weld element", "AWS A2.4:2020": "length (left of the hyphen)", "GB/T 324-2008 (ISO 1992 line)": "weld length", "Conflict": "C3", "Source": "S1, S6, S13" }, { "Letter": "n", "ISO 2553:2019": "number of weld elements", "AWS A2.4:2020": "not used (count in brackets)", "GB/T 324-2008 (ISO 1992 line)": "number of elements", "Conflict": "C3", "Source": "S1, S11, S13" }, { "Letter": "p", "ISO 2553:2019": "not used (e instead)", "AWS A2.4:2020": "pitch (centre distance)", "GB/T 324-2008 (ISO 1992 line)": "root face", "Conflict": "C4", "Source": "S1, S6, S13" }, { "Letter": "P", "ISO 2553:2019": "not used", "AWS A2.4:2020": "pitch", "GB/T 324-2008 (ISO 1992 line)": "not used", "Conflict": "C4", "Source": "S6" }, { "Letter": "L", "ISO 2553:2019": "not used", "AWS A2.4:2020": "length (length-pitch notation)", "GB/T 324-2008 (ISO 1992 line)": "not used", "Conflict": "C3", "Source": "S6" }, { "Letter": "R", "ISO 2553:2019": "root radius (U / J)", "AWS A2.4:2020": "root opening", "GB/T 324-2008 (ISO 1992 line)": "root radius", "Conflict": "C9", "Source": "S1, S6, S13" }, { "Letter": "b", "ISO 2553:2019": "root gap", "AWS A2.4:2020": "not used (R instead)", "GB/T 324-2008 (ISO 1992 line)": "root gap", "Conflict": "C9", "Source": "S1, S7, S13" }, { "Letter": "α", "ISO 2553:2019": "included angle", "AWS A2.4:2020": "groove angle", "GB/T 324-2008 (ISO 1992 line)": "groove angle", "Conflict": "—", "Source": "S1, S6, S13" }, { "Letter": "K", "ISO 2553:2019": "not used", "AWS A2.4:2020": "not used", "GB/T 324-2008 (ISO 1992 line)": "leg size", "Conflict": "C2", "Source": "S13" }, { "Letter": "H", "ISO 2553:2019": "not used", "AWS A2.4:2020": "not used", "GB/T 324-2008 (ISO 1992 line)": "groove depth", "Conflict": "C5", "Source": "S13" }, { "Letter": "h", "ISO 2553:2019": "not used", "AWS A2.4:2020": "not used", "GB/T 324-2008 (ISO 1992 line)": "weld face (reinforcement)", "Conflict": "—", "Source": "S13" }, { "Letter": "N", "ISO 2553:2019": "not used", "AWS A2.4:2020": "not used", "GB/T 324-2008 (ISO 1992 line)": "number of identical welds (in the tail)", "Conflict": "—", "Source": "S13" } ] }, { "caption": "What do the supplementary symbols and tail marks mean?", "columns": [ "Supplementary item", "ISO 2553", "AWS A2.4", "Meaning", "Reading note" ], "rows": [ { "Supplementary item": "Flat contour", "ISO 2553": "supplementary No.1", "AWS A2.4": "flat (fillets only) / flush (other welds, 2020)", "Meaning": "surface flush with the plate", "Reading note": "2020 split flat vs flush by weld type" }, { "Supplementary item": "Convex", "ISO 2553": "No.2", "AWS A2.4": "convex", "Meaning": "surface bulges", "Reading note": "drawn above the symbol" }, { "Supplementary item": "Concave", "ISO 2553": "No.3", "AWS A2.4": "concave", "Meaning": "surface hollows", "Reading note": "drawn above the symbol" }, { "Supplementary item": "Smooth blend", "ISO 2553": "No.4", "AWS A2.4": "no separate symbol (note)", "Meaning": "toes ground to a smooth transition", "Reading note": "ISO-only graphic; AWS by note" }, { "Supplementary item": "Weld-all-around", "ISO 2553": "No.10", "AWS A2.4": "circle at the elbow", "Meaning": "weld continues around the joint", "Reading note": "circle sits at the arrow-line/reference-line junction" }, { "Supplementary item": "Field weld", "ISO 2553": "No.12", "AWS A2.4": "flag at the elbow", "Meaning": "welded on site, not in the shop", "Reading note": "same junction position as all-around — meaning differs" }, { "Supplementary item": "Backing run / back weld", "ISO 2553": "No.5", "AWS A2.4": "§7.7 backing / back weld", "Meaning": "a seal pass welded from the far side", "Reading note": "backing run is welded; a backing strip is a part" }, { "Supplementary item": "Permanent backing", "ISO 2553": "No.7a", "AWS A2.4": "backing (permanent)", "Meaning": "strip stays in the joint", "Reading note": "symbol on the far side of the groove" }, { "Supplementary item": "Removable backing", "ISO 2553": "No.7c", "AWS A2.4": "removable backing (note)", "Meaning": "stripped after welding", "Reading note": "distinguish from permanent" }, { "Supplementary item": "Spacer", "ISO 2553": "No.8", "AWS A2.4": "spacer", "Meaning": "insert controlling the root gap", "Reading note": "drawn at the joint" }, { "Supplementary item": "Consumable insert", "ISO 2553": "No.9", "AWS A2.4": "consumable insert", "Meaning": "root insert becomes weld metal", "Reading note": "drawn at the root" }, { "Supplementary item": "Melt-through", "ISO 2553": "—", "AWS A2.4": "filled half-circle", "Meaning": "full penetration visible on the far side", "Reading note": "filled vs open half-circle is the AWS distinction" }, { "Supplementary item": "Finish designator", "ISO 2553": "note / tail", "AWS A2.4": "C G H M P R U", "Meaning": "C chipping, G grinding, H hammering, M machining, P planing, R rolling, U unspecified", "Reading note": "above the symbol or in the tail" }, { "Supplementary item": "Tail", "ISO 2553": "process / standard / quality / position, slash-separated", "AWS A2.4": "WPS / spec / reference", "Meaning": "the auxiliary-information slot", "Reading note": "empty = no reference (0 references)" }, { "Supplementary item": "Multiple reference lines", "ISO 2553": "sequence / multiple passes", "AWS A2.4": "operation order", "Meaning": "read in line order", "Reading note": "top-down or as annotated" }, { "Supplementary item": "Staggered intermittent welds", "ISO 2553": "Z mark on the line", "AWS A2.4": "offset symbols above/below", "Meaning": "alternating elements on the two faces", "Reading note": "do not confuse the ISO Z with a Z-groove" } ] }, { "caption": "How do you read a welding symbol left to right?", "columns": [ "No.", "Notation (described)", "System", "Literal reading", "Meaning" ], "rows": [ { "No.": "1", "Notation (described)": "[solid] a5 triangle", "System": "ISO A", "Literal reading": "triangle on the solid line; a5 on its left", "Meaning": "arrow-side fillet, throat 5 mm" }, { "No.": "2", "Notation (described)": "[dashed] a5 triangle", "System": "ISO A", "Literal reading": "triangle on the dashed line", "Meaning": "other-side fillet, throat 5 mm" }, { "No.": "3", "Notation (described)": "[solid] z6 triangle", "System": "ISO A", "Literal reading": "z6 on the solid line", "Meaning": "arrow-side fillet, leg 6 mm" }, { "No.": "4", "Notation (described)": "[below] 6 triangle", "System": "ISO B or AWS", "Literal reading": "triangle below a single line; bare 6 on the left", "Meaning": "arrow-side fillet, leg 6 mm (AWS S = 6)" }, { "No.": "5", "Notation (described)": "[above] 6 triangle", "System": "ISO B or AWS", "Literal reading": "triangle above the line", "Meaning": "other-side fillet, leg 6 mm" }, { "No.": "6", "Notation (described)": "[below] V 60° s10", "System": "ISO B", "Literal reading": "V below the line, 60° on the symbol, s10 left", "Meaning": "arrow-side single-V, 60° included, penetration 10 mm" }, { "No.": "7", "Notation (described)": "[above] V 60° D12(S10)", "System": "AWS", "Literal reading": "V above the line; D12 left, (S10) following", "Meaning": "other-side single-V, 12 mm deep, 10 mm effective throat" }, { "No.": "8", "Notation (described)": "[below] and [above] V (two)", "System": "ISO A/B or AWS", "Literal reading": "mirrored pair", "Meaning": "double-V — weld both sides, no side meaning" }, { "No.": "9", "Notation (described)": "[below] circle d6, n × (50)", "System": "ISO B", "Literal reading": "hollow circle centred; d6 left; n × (50) right", "Meaning": "spot series: 6 mm nuggets, count and 50 mm spacing per the right-hand notation" }, { "No.": "10", "Notation (described)": "[below] rectangle d10 (8)", "System": "ISO B", "Literal reading": "rectangle below; d10 left; (8) inside", "Meaning": "plug weld: 10 mm hole, 8 mm fill (omit the depth = fill flush)" }, { "No.": "11", "Notation (described)": "[below] wavy line", "System": "ISO B or AWS", "Literal reading": "wavy line below", "Meaning": "surfacing / wear layer" }, { "No.": "12", "Notation (described)": "[below] three parallel lines", "System": "ISO B", "Literal reading": "three short vertical lines below", "Meaning": "edge weld" }, { "No.": "13", "Notation (described)": "[below] two flaring lines", "System": "ISO B", "Literal reading": "outward-flaring pair below", "Meaning": "flanged edge weld, fully melted" }, { "No.": "14", "Notation (described)": "[below] triangle + circle at the elbow", "System": "both", "Literal reading": "circle at the arrow/reference junction", "Meaning": "arrow-side fillet, welded all around" }, { "No.": "15", "Notation (described)": "[below] triangle + flag at the elbow", "System": "both", "Literal reading": "flag at the junction", "Meaning": "arrow-side fillet, field weld" }, { "No.": "16", "Notation (described)": "[tail] 135 / ISO 5817-B / PF", "System": "ISO", "Literal reading": "forked tail, slash-separated", "Meaning": "process 135 (MAG), quality B (ISO 5817), position PF" }, { "No.": "17", "Notation (described)": "two reference lines, symbols on each", "System": "AWS", "Literal reading": "two parallel reference lines", "Meaning": "operations in line order (multi-pass sequence)" }, { "No.": "18", "Notation (described)": "[below] triangle 6-75/150", "System": "AWS", "Literal reading": "6 left of the triangle; 75-150 right", "Meaning": "intermittent arrow-side fillet: leg 6, 75 mm elements at 150 mm pitch" } ] }, { "caption": "What does p mean — pitch, gap or root face?", "columns": [ "Document", "p means", "Applies to" ], "rows": [ { "Document": "AWS A2.4", "p means": "pitch — centre-to-centre", "Applies to": "AWS intermittent, spot and plug series" }, { "Document": "ISO 2553", "p means": "not used — clear gap is e", "Applies to": "ISO intermittent notation" }, { "Document": "GB/T 324-2008", "p means": "root face", "Applies to": "Chinese national standard / old ISO-1992-line drawings only" }, { "Document": "shop speech", "p means": "often pitch, written casually", "Applies to": "fine for conversation — never for drawing interpretation" } ] } ] }