Arc: The curved portion of a bend.
Arc Length: The length of a bent/rolled surface.


Bend Radius: The arc of the bend itself, usually taken at the centerline. The distance from the center of curvature to the centerline (axis) of the pipe, expressed as a number multiplied by the pipe or tube size. For example, the bend radius of a 5 × D bend for a 2-inch nominal pipe size (NPS) pipe or a 2-inch tube is 10 inches (see centerline radius).


Center to Center: The distance between the theoretical or calculated centers of two adjoining bends on the same plane. Also used for diametric measurement between the centerlines of two tangent points of a bend (i.e. 180° bend, for which the center to center distance will be equal to twice the centerline radius).
Centerline Radius: The distance from the center of the curvature to the centerline (axis) of the pipe.
Chord: The straight distance measured between the centerline points of any two points of a bend.
Cold Bending ("Pyramid" Rolling): A steel member is placed in a machine and curved between three rolls.


Degree of Bend: The angle to which the bend is formed.
Diameter: A straight line passing through the center of a circle.
Distortion: A change from original shape and dimension. Note: Occurs in every rolled part to some degree.
Ductility: The ability of the material to deform without fracture. This is measured by elongation of reduction of area in a tensile test.


Hot Bending: Bending is achieved by applying heat directly to material by internal or external flame, or heating in a furnace.


Induction Bending: An electric coil heats a short section of a structural member, and then it is drawn through a process similar to rotary-draw and cooled with water directly after.


Off-Axis: Material rotated out of square in a cross sectional view.
Ovality: The distortion of the cross section of pipe or tube from its normal (round) shape usually expressed as a percentage of the difference between major and minor axis.


Point Bending/Gag Pressing: Bending is achieved by applying a select number of point loads at varying increments along the length of the steel member.


Radius: A line segment that joins the center of a circle with any point on the materials circumference (see centerline radius).
Rise/Mid Ordinate: The distance of offset between the mid point of a chord and an arc, perpendicular to the chord.
Rotary-Draw Bending: The structural material is clamped into a die and then drawn around the die and over a mandrel until the bend is formed.


S-Curve: Bends occur in the same plane, but in opposite directions.
Slope: Calculated as the rise over the run of a segment.
Spirals: Bends occurs in a plan view with rise in elevation view.
Synchronized Incremental Cold Bending: Performed by applying pressure in a highly synchronized fashion at several locations along the steel member.


Tangent: Straight section of material on either side of the bend or arc. May be any length. In order to make the bend itself, there has to be sufficient material at each end during the bending process. Excess may be trimmed after.
Tangent Point: The point at which the bend is started or ended.


Wall: The thickness of tubular material, usually expressed as "nominal" or "minimum."
Wall Thickness: The thickness of the material.
Wrinkles: Definite folds, creases or ripples formed on the surface of the pipe during bending operation.


Yield Point: The point at which material will deform permanently during bending.
Yield Strength: The stress at which a material exhibits a specified deviation.