{
 "version": "2026-10-20",
 "license": "Dimension sheets: CC BY 4.0. Standard and published-size files: CC BY 4.0. Xem Studio's own designs (files_license = Xem Studio Design License): free to use and sell things from, not to redistribute as files — https://xemstudio.com/license/. Other publishers' files: their own license, linked beside them.",
 "slug": "butt-weld-return-bends-180",
 "name": "Butt-weld 180° return bends, long and short radius (ASME B16.9), NPS 1/2 to 12: centre-to-centre O and back-to-face K",
 "kind": "standard",
 "category": "Tri-clamp & pipe",
 "group": "Pipe, tube & threads",
 "year": null,
 "question": "What are the dimensions of a 180° return bend (U-bend): centre-to-centre and back-to-face?",
 "tags": [
  "pipe",
  "pipe fitting",
  "butt weld",
  "return bend",
  "180 elbow",
  "u-bend",
  "b16.9",
  "standard"
 ],
 "aliases": [
  "180 degree return bend dimensions",
  "180 elbow center to center",
  "u bend pipe fitting dimensions",
  "180 return bend long radius",
  "180 return bend short radius",
  "b16.9 return bend",
  "return bend back to face",
  "2 inch 180 degree elbow",
  "180 elbow step file",
  "weld return bend sch 40"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": false,
 "free_files": 6,
 "url": "https://xemstudio.com/objects/butt-weld-return-bends-180/",
 "sheet_txt": "https://xemstudio.com/objects/butt-weld-return-bends-180/sheet.txt",
 "sheet": {
  "basis": "Long-radius O and K (mm) and short-radius O and K (mm) from Wermac's ASME B16.9 return-bend table; long-radius inch values (V, W) from Texas Flange; OD and Schedule 40 wall per ASME B36.10",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "A 180° return bend is two straight-pipe ends 'U-turned': O is the centre-to-centre distance between the two ends and K the back-to-face distance (outside of the bend to the weld faces). Long radius has O = 3 × NPS (the bend radius is 1.5 × NPS, as for a long-radius elbow); short radius has O = 2 × NPS (bend radius 1 × NPS). Wermac prints short radius from NPS 1 up; there is no SR row at NPS 1/2 or 3/4.",
   "Wermac's mm table and Texas Flange's inch table (printed as V centre-to-centre and W back-to-face, same for all schedules) agree for the long-radius bend in every size. Texas Flange's short-radius page was not read, so SR is Wermac only.",
   "Files at NPS 1, 2 and 4, Schedule 40, hollow, long radius and short radius: a half torus whose bend radius is half the published O (long radius: the Texas Flange inch value; short radius: Wermac's mm value), with both end faces in one plane. K is not an input: the model's back-to-face (bend radius + OD/2) is within 1.5 mm of the published K for all six files (NPS 1 long radius: model 54.8 vs 56 published).",
   "OD and Schedule 40 wall: the tables print OD rounded (1.32, 2.38, 4.50 in); the files use the exact ASME B36.10 OD (1.315, 2.375, 4.500 in) with the Sch 40 wall (.133, .154, .237 in) that Texas Flange prints for each size. Fittings are made to match the pipe's OD and wall.",
   "Ends are drawn square. Real fittings are bevelled for welding to ASME B16.25; no public, citable statement of the bevel was found, so it is not drawn."
  ],
  "table": {
   "columns": [
    "NPS",
    "OD, mm",
    "LR centre-to-centre O, mm",
    "LR back-to-face K, mm",
    "LR O, in (Texas Flange V)",
    "LR K, in (Texas Flange W)",
    "SR O, mm",
    "SR K, mm"
   ],
   "rows": [
    [
     "1/2",
     "21.3 (0.84 in)",
     "76",
     "48",
     "3.00",
     "1.88",
     "—",
     "—"
    ],
    [
     "3/4",
     "26.7 (1.05 in)",
     "76",
     "51",
     "3.00",
     "2.00",
     "—",
     "—"
    ],
    [
     "1",
     "33.4 (1.32 in)",
     "76",
     "56",
     "3.00",
     "2.19",
     "51",
     "41"
    ],
    [
     "1-1/4",
     "42.2 (1.66 in)",
     "95",
     "70",
     "3.75",
     "2.75",
     "64",
     "52"
    ],
    [
     "1-1/2",
     "48.3 (1.90 in)",
     "114",
     "83",
     "4.50",
     "3.25",
     "76",
     "62"
    ],
    [
     "2",
     "60.3 (2.38 in)",
     "152",
     "106",
     "6.00",
     "4.19",
     "102",
     "81"
    ],
    [
     "2-1/2",
     "73.0 (2.88 in)",
     "190",
     "132",
     "7.50",
     "5.19",
     "127",
     "100"
    ],
    [
     "3",
     "88.9 (3.50 in)",
     "229",
     "159",
     "9.00",
     "6.25",
     "152",
     "121"
    ],
    [
     "3-1/2",
     "101.6 (4.00 in)",
     "267",
     "184",
     "10.50",
     "7.25",
     "178",
     "140"
    ],
    [
     "4",
     "114.3 (4.50 in)",
     "305",
     "210",
     "12.00",
     "8.25",
     "203",
     "159"
    ],
    [
     "5",
     "141.3 (5.56 in)",
     "381",
     "262",
     "15.00",
     "10.31",
     "254",
     "197"
    ],
    [
     "6",
     "168.3 (6.62 in)",
     "457",
     "313",
     "18.00",
     "12.31",
     "305",
     "237"
    ],
    [
     "8",
     "219.1 (8.62 in)",
     "610",
     "414",
     "24.00",
     "16.31",
     "406",
     "313"
    ],
    [
     "10",
     "273.0 (10.75 in)",
     "762",
     "518",
     "30.00",
     "20.38",
     "508",
     "391"
    ],
    [
     "12",
     "323.8 (12.75 in)",
     "914",
     "619",
     "36.00",
     "24.38",
     "610",
     "467"
    ]
   ]
  }
 },
 "sheet_text": "Butt-weld 180° return bends, long and short radius (ASME B16.9), NPS 1/2 to 12: centre-to-centre O and back-to-face K — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/butt-weld-return-bends-180/  (sheet CC BY 4.0)\nBasis: Long-radius O and K (mm) and short-radius O and K (mm) from Wermac's ASME B16.9 return-bend table; long-radius inch values (V, W) from Texas Flange; OD and Schedule 40 wall per ASME B36.10\nCatalog version: 2026-10-20\n\nSizes: see table below\n- A 180° return bend is two straight-pipe ends 'U-turned': O is the centre-to-centre distance between the two ends and K the back-to-face distance (outside of the bend to the weld faces). Long radius has O = 3 × NPS (the bend radius is 1.5 × NPS, as for a long-radius elbow); short radius has O = 2 × NPS (bend radius 1 × NPS). Wermac prints short radius from NPS 1 up; there is no SR row at NPS 1/2 or 3/4.\n- Wermac's mm table and Texas Flange's inch table (printed as V centre-to-centre and W back-to-face, same for all schedules) agree for the long-radius bend in every size. Texas Flange's short-radius page was not read, so SR is Wermac only.\n- Files at NPS 1, 2 and 4, Schedule 40, hollow, long radius and short radius: a half torus whose bend radius is half the published O (long radius: the Texas Flange inch value; short radius: Wermac's mm value), with both end faces in one plane. K is not an input: the model's back-to-face (bend radius + OD/2) is within 1.5 mm of the published K for all six files (NPS 1 long radius: model 54.8 vs 56 published).\n- OD and Schedule 40 wall: the tables print OD rounded (1.32, 2.38, 4.50 in); the files use the exact ASME B36.10 OD (1.315, 2.375, 4.500 in) with the Sch 40 wall (.133, .154, .237 in) that Texas Flange prints for each size. Fittings are made to match the pipe's OD and wall.\n- Ends are drawn square. Real fittings are bevelled for welding to ASME B16.25; no public, citable statement of the bevel was found, so it is not drawn.\n\nNPS  OD, mm  LR centre-to-centre O, mm  LR back-to-face K, mm  LR O, in (Texas Flange V)  LR K, in (Texas Flange W)  SR O, mm  SR K, mm\n1/2  21.3 (0.84 in)  76  48  3.00  1.88  —  —\n3/4  26.7 (1.05 in)  76  51  3.00  2.00  —  —\n1  33.4 (1.32 in)  76  56  3.00  2.19  51  41\n1-1/4  42.2 (1.66 in)  95  70  3.75  2.75  64  52\n1-1/2  48.3 (1.90 in)  114  83  4.50  3.25  76  62\n2  60.3 (2.38 in)  152  106  6.00  4.19  102  81\n2-1/2  73.0 (2.88 in)  190  132  7.50  5.19  127  100\n3  88.9 (3.50 in)  229  159  9.00  6.25  152  121\n3-1/2  101.6 (4.00 in)  267  184  10.50  7.25  178  140\n4  114.3 (4.50 in)  305  210  12.00  8.25  203  159\n5  141.3 (5.56 in)  381  262  15.00  10.31  254  197\n6  168.3 (6.62 in)  457  313  18.00  12.31  305  237\n8  219.1 (8.62 in)  610  414  24.00  16.31  406  313\n10  273.0 (10.75 in)  762  518  30.00  20.38  508  391\n12  323.8 (12.75 in)  914  619  36.00  24.38  610  467\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Wermac: ASME B16.9 180 deg long- and short-radius return bend dimensions (mm) — web — Publisher's page; dimensions are facts — https://wermac.org/fittings/dim_elbows_c.html\n- Texas Flange (manufacturer / distributor): Butt-weld 180 deg long-radius return bends: centre-to-centre and back-to-face by NPS — web — Publisher's page; dimensions are facts — https://texasflange.com/butt-weld-fittings/return-bend-180-long-radius/\n- McMaster-Carr: Metal pipe fittings (butt-weld elbows, tees, reducers, caps) (free STEP/IGES per part, for your own design use; no redistribution) — STEP, IGES, PDF — McMaster-Carr site terms: personal design use, no redistribution [verify license at link] — https://www.mcmaster.com/products/metal-pipe-fittings/\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 6 parts): https://xemstudio.com/files/hardware/butt-weld-return-bends-180/index.json\nAPI: https://xemstudio.com/api/geometry?object=butt-weld-return-bends-180\n",
 "sources": [
  {
   "publisher": "Wermac",
   "title": "ASME B16.9 180 deg long- and short-radius return bend dimensions (mm)",
   "url": "https://wermac.org/fittings/dim_elbows_c.html",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Texas Flange (manufacturer / distributor)",
   "title": "Butt-weld 180 deg long-radius return bends: centre-to-centre and back-to-face by NPS",
   "url": "https://texasflange.com/butt-weld-fittings/return-bend-180-long-radius/",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "McMaster-Carr",
   "title": "Metal pipe fittings (butt-weld elbows, tees, reducers, caps) (free STEP/IGES per part, for your own design use; no redistribution)",
   "url": "https://www.mcmaster.com/products/metal-pipe-fittings/",
   "formats": [
    "STEP",
    "IGES",
    "PDF"
   ],
   "license": "McMaster-Carr site terms: personal design use, no redistribution",
   "license_verified": false,
   "hosted": false
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "butt-weld-elbows-long-radius",
  "butt-weld-elbows-short-radius",
  "butt-weld-elbows-3d",
  "butt-weld-equal-tees",
  "schedule-40-pipe"
 ],
 "fits": [],
 "dimensions": "exact (nominal, no tolerance added)",
 "dimension_rule": "All geometry on Xem Studio is exact (nominal, true size) with no tolerance added. Where a part meets another part, the object lists its mating features (feature, exact size, what it mates with, fit class: press, slide, run, socket, clamp or designed). Apply your process's allowance to those features only; 'designed' gaps are part of the design and stay as drawn. Typical accuracy by process and ISO 286 fits: https://xemstudio.com/tolerances/",
 "mating": [
  {
   "feature": "weld ends",
   "exact": "OD = pipe OD (Ø33.40 / Ø60.33 / Ø114.30 at NPS 1 / 2 / 4), wall = Sch 40 (3.38 / 3.91 / 6.02)",
   "mates": "Schedule 40 pipe of the same NPS, butt-welded (schedule-40-pipe)",
   "fit": "designed",
   "files": "bw-return-180"
  },
  {
   "feature": "end spacing O",
   "exact": "LR 76.2 / 152.4 / 304.8; SR 51 / 102 / 203 (centre-to-centre)",
   "mates": "two parallel pipe runs at that spacing",
   "fit": "designed",
   "files": "bw-return-180"
  }
 ],
 "fit_classes": {
  "press": "stays put: pin, tube, bearing or magnet held by interference. ISO 286 equivalent: H7/p6 (locational interference) or tighter.",
  "slide": "assembles by hand and is held by a grub, pinch or clamp: shaft in a hub, rod in a socket, spigot in a bore. ISO 286 equivalent: H7/g6 or H7/h6.",
  "run": "turns or slides in use: pin in a link, rod through a guide. ISO 286 equivalent: H8/f7 (close running).",
  "socket": "large sliding fit: syringe barrel, sleeve, bobbin in a bore. ISO 286 equivalent: H9/d9 (free running) or looser.",
  "clamp": "split part that closes on the mating part with screws: make it at size.",
  "designed": "a gap that is part of the design (piston fit option, displacer gap, air gap): do not change."
 },
 "faq": [
  {
   "q": "What is the centre-to-centre of a 2 inch 180° long-radius return bend?",
   "a": "152 mm (6.00 in); back-to-face K is 106 mm (4.19 in)."
  },
  {
   "q": "What is the centre-to-centre of a 2 inch short-radius 180° return?",
   "a": "102 mm (Wermac); back-to-face 81 mm."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "bw-return-180-lr-nps1-sch40",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/butt-weld-return-bends-180/bw-return-180-lr-nps1-sch40.step",
   "stl": "https://xemstudio.com/files/hardware/butt-weld-return-bends-180/bw-return-180-lr-nps1-sch40.stl",
   "note": "NPS 1 Sch 40 180° long-radius return bend: OD 33.40 × 3.38 wall, centre-to-centre 76.2 mm; ends square, both end faces in one plane"
  },
  {
   "file": "bw-return-180-sr-nps1-sch40",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/butt-weld-return-bends-180/bw-return-180-sr-nps1-sch40.step",
   "stl": "https://xemstudio.com/files/hardware/butt-weld-return-bends-180/bw-return-180-sr-nps1-sch40.stl",
   "note": "NPS 1 Sch 40 180° short-radius return bend: OD 33.40 × 3.38 wall, centre-to-centre 51.0 mm; ends square, both end faces in one plane"
  },
  {
   "file": "bw-return-180-lr-nps2-sch40",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/butt-weld-return-bends-180/bw-return-180-lr-nps2-sch40.step",
   "stl": "https://xemstudio.com/files/hardware/butt-weld-return-bends-180/bw-return-180-lr-nps2-sch40.stl",
   "note": "NPS 2 Sch 40 180° long-radius return bend: OD 60.32 × 3.91 wall, centre-to-centre 152.4 mm; ends square, both end faces in one plane"
  },
  {
   "file": "bw-return-180-sr-nps2-sch40",
   "formats": [
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   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/butt-weld-return-bends-180/bw-return-180-sr-nps2-sch40.step",
   "stl": "https://xemstudio.com/files/hardware/butt-weld-return-bends-180/bw-return-180-sr-nps2-sch40.stl",
   "note": "NPS 2 Sch 40 180° short-radius return bend: OD 60.32 × 3.91 wall, centre-to-centre 102.0 mm; ends square, both end faces in one plane"
  },
  {
   "file": "bw-return-180-lr-nps4-sch40",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/butt-weld-return-bends-180/bw-return-180-lr-nps4-sch40.step",
   "stl": "https://xemstudio.com/files/hardware/butt-weld-return-bends-180/bw-return-180-lr-nps4-sch40.stl",
   "note": "NPS 4 Sch 40 180° long-radius return bend: OD 114.30 × 6.02 wall, centre-to-centre 304.8 mm; ends square, both end faces in one plane"
  },
  {
   "file": "bw-return-180-sr-nps4-sch40",
   "formats": [
    "step",
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   ],
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   "stl": "https://xemstudio.com/files/hardware/butt-weld-return-bends-180/bw-return-180-sr-nps4-sch40.stl",
   "note": "NPS 4 Sch 40 180° short-radius return bend: OD 114.30 × 6.02 wall, centre-to-centre 203.0 mm; ends square, both end faces in one plane"
  }
 ],
 "markdown": "https://xemstudio.com/objects/butt-weld-return-bends-180/index.md"
}