# 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

> What are the dimensions of a 180° return bend (U-bend): centre-to-centre and back-to-face?

- Category: Tri-clamp & pipe › Pipe, tube & threads
- Kind: Standard part
- 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
- Page: https://xemstudio.com/objects/butt-weld-return-bends-180/ · JSON: https://xemstudio.com/api/geometry?object=butt-weld-return-bends-180 · Plain text: https://xemstudio.com/objects/butt-weld-return-bends-180/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files CC BY 4.0 or their publisher's license
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

**Exact dimensions.** Every file is drawn at true size with no tolerance added. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your process's clearance before making the part.

## 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.

## Mating features (exact size; open press / slide / run / socket by your process clearance, leave designed and clamp as drawn)

| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| weld ends | OD = pipe OD (Ø33.40 / Ø60.33 / Ø114.30 at NPS 1 / 2 / 4), wall = Sch 40 (3.38 / 3.91 / 6.02) | Schedule 40 pipe of the same NPS, butt-welded (schedule-40-pipe) | designed | bw-return-180* |
| end spacing O | LR 76.2 / 152.4 / 304.8; SR 51 / 102 / 203 (centre-to-centre) | two parallel pipe runs at that spacing | designed | bw-return-180* |

## Sizes

| 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 |

## Where the files are

- Wermac: [ASME B16.9 180 deg long- and short-radius return bend dimensions (mm)](https://wermac.org/fittings/dim_elbows_c.html) — web — Publisher's page; dimensions are facts
- Texas Flange (manufacturer / distributor): [Butt-weld 180 deg long-radius return bends: centre-to-centre and back-to-face by NPS](https://texasflange.com/butt-weld-fittings/return-bend-180-long-radius/) — web — Publisher's page; dimensions are facts
- McMaster-Carr: [Metal pipe fittings (butt-weld elbows, tees, reducers, caps) (free STEP/IGES per part, for your own design use; no redistribution)](https://www.mcmaster.com/products/metal-pipe-fittings/) — STEP, IGES, PDF — McMaster-Carr site terms: personal design use, no redistribution (verify at link)

## Free STEP/STL (6 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/butt-weld-return-bends-180/index.json

- bw-return-180-lr-nps1-sch40: [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) — 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
- bw-return-180-sr-nps1-sch40: [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) — 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
- bw-return-180-lr-nps2-sch40: [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) — 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
- bw-return-180-sr-nps2-sch40: [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) — 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
- bw-return-180-lr-nps4-sch40: [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) — 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
- bw-return-180-sr-nps4-sch40: [STEP](https://xemstudio.com/files/hardware/butt-weld-return-bends-180/bw-return-180-sr-nps4-sch40.step) · [STL](https://xemstudio.com/files/hardware/butt-weld-return-bends-180/bw-return-180-sr-nps4-sch40.stl) — 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

## Questions

**What is the centre-to-centre of a 2 inch 180° long-radius return bend?**

152 mm (6.00 in); back-to-face K is 106 mm (4.19 in).

**What is the centre-to-centre of a 2 inch short-radius 180° return?**

102 mm (Wermac); back-to-face 81 mm.

## Fits with

- [Butt-weld elbows, 90° and 45° long radius (ASME B16.9), NPS ½ to 12](https://xemstudio.com/objects/butt-weld-elbows-long-radius/)
- [Butt-weld short-radius 90° elbows (ASME B16.9 / B16.28), NPS 1 to 12: centre-to-end = 1 × NPS](https://xemstudio.com/objects/butt-weld-elbows-short-radius/)
- [Butt-weld 3D (3R) elbows, 90° and 45° (ASME B16.9), NPS 3/4 to 12: centre-to-end 3 × NPS](https://xemstudio.com/objects/butt-weld-elbows-3d/)
- [Butt-weld equal tees (ASME B16.9), NPS ½ to 12](https://xemstudio.com/objects/butt-weld-equal-tees/)
- [Schedule 40 pipe and PVC fittings, 1/2 to 2 inch](https://xemstudio.com/objects/schedule-40-pipe/)