Tube bending can be one of the most complex industries there is. Here you will find a list of commonly used tube bending terms to help you get to grips with the basic concepts.
On a rotary draw tube bending machine, CCW refers to the direction of rotation of the bend arm swing when moving counter-clockwise.
On a rotary draw tube bending machine, CW refers to the direction of rotation of the bend arm swing when moving clockwise.
Centre line height can refer to one of two measurements:
The height of the centre of the tube groove from the floor
The height from the bottom of the bend die to the centre of the tube groove on the die
The radius around which the tube is bent, measured from the centreline of the tube.
Tooling design where the groove in the bend die and wiper die is deeper than half the tube diameter. Used with interlock tooling in high-precision aerospace applications to minimise tool marks in ultra-thin wall tubing.
A surface treatment applied to bend die grip sections and clamp dies to increase friction and reduce tube slippage during bending.
Tooling designed for very short DBB (distance between bends), where the previous bend is machined into the bend die grip and clamp die. More expensive, but essential for high-production applications where short grip lengths are impractical.
The number of degrees through which a tube is bent.
A ratio calculated by dividing the centreline radius (CLR) by the tube or pipe outside diameter (OD).
The distance between the tangent point of one bend and the tangent point of the next bend.
When bending rectangular tube with the section standing vertically in the bend die. This orientation is easier to bend and produces less distortion.
Refers to the direction of bend for rectangular tube when the tube stands vertically in the bend die.
Material transfer caused by high pressure and friction. Common when bending stainless steel with steel tooling or aluminium with aluminium-bronze tooling. Reduced by improved lubrication, alternative tooling materials, or slower bend arm rotation.
A method of specifying pipe wall thickness using a standard gauge system rather than millimetres or inches. Gauge charts are required for conversion.
When bending rectangular tube with the section lying horizontally in the bend die. This orientation increases forming difficulty and distortion risk.
Refers to the direction of bend for rectangular tube when the tube lies horizontally in the bend die.
The straight section of the bend die groove between the grip section and the tangent point, when the grip section is removable.
Commonly used for square and rectangular tube.
ISR = CLR minus half the tube OD
An aggressive surface treatment applied to bend die grip sections and clamp dies to prevent slippage. Available in fine or coarse patterns. Provides grip without deforming the tube like serration.
A tube description method based on Length, Rotation and Angle (also known as YBC). Defines how far to feed the tube, how much to rotate it, and how many degrees to bend.
A system used to specify pipe wall thickness based on nominal pipe size. Schedule charts are required for accurate dimensional reference.
The amount of rotation between two bends, specified in degrees.
After bending, the tube springs back and the final radius becomes larger than the bend die CLR. Radial growth increases with larger CLRs and harder materials. Tooling can compensate if material springback is known.
High-precision tooling where the wiper die, clamp die and pressure die interlock into the bend die. Used for cosmetic, aerospace and high-production applications.
A vertical groove surface treatment applied to grip sections and clamp dies to prevent slippage. Effective with short grip lengths but will mark and deform the tube.
The tendency of material to return toward its original shape after bending. Springback varies depending on material type, wall thickness and CLR.
The internal diameter of the tube.
The external diameter of the tube.
Tube OD divided by wall thickness. Used to assess bend difficulty and tooling requirements.
The thickness of the tube wall, specified in millimetres, inches, gauge or pipe schedule.
A tooling component fitted behind the bend former that traps the tube between itself and the pressure die. Prevents wrinkling on the inside of tight-radius bends.
A tube description method based on Cartesian coordinates (X, Y and Z axes) to define tube geometry in three-dimensional space.
