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 Source: Xem Studio, https://xemstudio.com/objects/butt-weld-return-bends-180/ (sheet CC BY 4.0) 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 Catalog version: 2026-10-20 Sizes: see table below - 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. 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 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 Files elsewhere (not hosted by Xem Studio; license as stated by the publisher): - 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 - 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/ - 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/ Free files (CC BY 4.0, Xem Studio; STEP + STL, 6 parts): https://xemstudio.com/files/hardware/butt-weld-return-bends-180/index.json API: https://xemstudio.com/api/geometry?object=butt-weld-return-bends-180