Bend Cutting — Companion Article
Open the tool: https://pipingdesigners.com/tools-training/bend-cutting/
What this tool does
Bend Cutting gives the shop geometry for a mitre bend and for cutting a formed elbow to a smaller angle. It returns cut angles, cutbacks, piece lengths, a wrap-around template and a sketch.
It is shop geometry only. It does not design the wall for pressure.
When to use it
Use it to mark out a mitre bend on large pipe or ducting, or to cut a 90° elbow down to a non-standard angle in the field.
Inputs
- Mode: mitre bend, or elbow cut.
- Outside diameter D and bend radius R.
- Bend angle.
- Mitre: number of segments, or a maximum angle per joint.
- Units: metric or US customary.
How it works
For a mitre, cuts = segments − 1, and each cut is at α = bend angle / (2 × cuts) from square. The full cutback is D × tan(α). End pieces are R × α long on the centreline, and middle pieces are twice that.
The wrap template gives the cut height at equal divisions around the pipe, from zero at the short point to the full cutback at the long point.
For an elbow cut, the cut is square to the centreline. The page gives the kept lengths along the outside, centre and inside, and the offcut.
Understanding the result
Print or copy the template ordinates onto a paper wrap and mark the pipe from it. The sketch shows the pieces and the cut lines.
Engineering considerations
- Mitre bends have higher stress than smooth bends. The code limits them. Check before using one on pressure piping.
- Add your weld gap and bevel to the cut pieces.
Example
A two-piece 90° mitre is cut at 45°, and the full cutback equals D. A three-piece 90° mitre is cut at 22.5°.
Standards/references (licensed vs interim)
Geometry only. No standard table is stored. Mitre bend pressure design is covered in ASME B31.3, and is not done on this page.
Limitations/disclaimer
- No pressure design.
- No fitting dimension table.
- The result is preliminary and needs engineering review.
Use the tool
Calculate now: Bend Cutting
Related tools
- Bend Wall Thickness (new tool, being added to the site).
- Pipe Offset (new tool, being added to the site).