Arc- The portion of the metal that is curved. This could be a steel beam, a tube, a pipe, a square tube or even sheet metal.

Arc Length- The length of the portion of the metal that is curved to the required radius.

Arc Length

Chord- A line segment that joins two points on a curve. In our case from one end of the arc to the other end of the arc.

CLR- Centerline radius of the rolled shape.

Compound Bend- See Compound Radius.

Compound Radius- More than one radius.

Compound Radius

Degree- Indicates the size of the spiral stair.

Degrees (of arc)- The portion of a circle, stated in degrees. For example:

Equal Tangent- When the straight portions at each end of an arc are equal. (Also see Tangent.)

Good Arc- The portion of the steel or other metal that is curved to the required radius.

Hot Forming- Heated metal is formed around a die. Some applications may not allow heat. Hot Forming allows for bending steel tighter than otherwise impossible.

IR- Inside radius of the rolled shape.

Landing- The intermediate platform on a flight of stairs or the area at the top or bottom of a staircase.

Leg- Side of a cross section that is not hollow.

Mandrel Bending- Cold steel or other metal is formed around a die using a mandrel. Limited to 180 degree bends. Mandrel bending can bend hollow sections of steel very tight.

Minimum Tangent- Minimum required straight portion at the end of an arc. (Also see Tangent.)

Ovality- Distortion of pipe or round tube from its normal, round shape to an oval shape. This is caused by the rolling process.

OR- Outside radius of the rolled shape.

Plan Radius- Radius in a spiral stair that is on the floor.

Pitch- Indicates the angle of rise for the spiral stair.

Radius- Distance from the center of a circle to any point on its circumference.

Ripple- Distortion caused by rolling.

RPD- Roll per drawing.

Rolling- Cold steel or other metal is fed through machines that utilize three rolling dies. Rolling can’t bend as tight as some other methods. Allows for 360 degree bends.

S Bend- A compound radius where one radius is opposite the other.

S Bend

Spiral Staircase- A staircase that is curved.

Tangent- Straight portion at the end of an arc


Total Rise- Distance from floor to floor in a spiral stair.

True Radius- Radius of a spiral stair as the stair rises.

Up Clockwise/Up Counterclockwise- Direction the spiral stair rises.

Wall- Side of a cross section that is hollow.

Questions about these or any other steel-bending or metal bending industry terms? Please call us for more information. . We are eager to help you understand what goes into the steel-bending process, and we will be happy fulfill all your metal bending, steel forming and tube, pipe, beam and angle rolling needs.

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