---
title: Tube Bending Formulas & Common Terms | Tubular Components Design
description: A list of tube bending formulas & common tube bending terms to help you optimize your tubular components design.
---

[McHone Industries Blog](https://www.mchoneind.com/blog)

# [Tube Bending Formulas & Common Terms | Tubular Components Design](https://www.mchoneind.com/blog/tube-bending-formulas-tubular-components-design)

 Written by [McHone Industries, Inc.](https://www.mchoneind.com/blog/author/mchone-industries-inc) | Apr 18, 2017 5:34:24 PM

This guide to tube bending formulas will help you optimize your tubular components. [Download the full guide here](https://www.mchoneind.com/tube-bending-design-guide-download) for a complete list of dos and don'ts.

If you have any questions about designing for tube bending, feel free to [contact us directly](https://blog.mchoneind.com/contact-us).

## Tubing Bending Formulas & Common Terms

### [Download full design guide](https://www.mchoneind.com/tube-bending-design-guide-download)

###   [DOWNLOAD FULL DESIGN GUIDE](https://www.mchoneind.com/tube-bending-design-guide-download)

 

### common terms & Constants

1. ** Centerline Radius (CLR)** - the neutral line; will not stretch or compress during bending
2. ** Outer Diameter (OD)**  - length and width of tube measured from the outside wall
3. ** "D" of Bend** - ratio between CLR and outside diameter
4. **  Wall Thickness (WT)** - thickness of tube wall measured in inches or millimeters
5. ** Gauge** - thickness of tube wall as a standard integer (0.049" WT = 18 gauge)
6. ** Ovality** - difference between max OD and min OD on a bend section
7. ** Inside Bend Radius (intrados)** - measurement of the inside curve of a bend
8. ** Outside Bend Radius (extrados)** - measurement of the outside curve of a bend

 

### Common Methods for Defining Tube Shapes

**1.  XYZ Method**

General method for defining tube shape, based on three-dimensional mathematical planes. Used alongside LRA method to optimize design for production.

<http://www.ercolinacnc.com/>  
*Image from [Ercolina CNC](http://www.ercolinacnc.com/)*

**2.  LRA or Bend Data Method**

Common method of defining tube shapes when bending is involved. Complements XYZ measurements. Uses three elements to define shape: DBB, DOB, and POB.

**L / DBB:** distance between bends; where one bend ends and another starts to curve

**R / POB:** plane of bend; rotational relationship between one bend plane and the next; defined in degrees

**A / DOB:** angle of bend, measured in degrees

### useful equations

1. **"D" of Bend:**  CLR / OD
2. **Inside Diameter:**  OD - (WT - 2)
3. **Inside Radius:**  CLR - (OD / 2)
4. **Outside Radius:**  CLR + (OD / 2)
5. **Wall Factor:**  OD / WT
6. **Extrados Wall Thinning %:**  (Outside Radius - CLR) / Outside Radius
7. **Percentage Elongation at Arc of Bend:**  (Outside Radius / CLR) - 1
8. **Ovality:**  Max OD - min OD

## Tubular Components Design Guide

Want the full scoop on designing tubular components for bending? Download the guide today.

[View full post](https://www.mchoneind.com/blog/tube-bending-formulas-tubular-components-design)

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