machines used for straightening metal items. There are several types of straighteners.

Parallel-roll straighteners have two parallel rows of rolls arranged in a staggered pattern (Figure 1). Such straighteners are commonly used for straightening both sheet and section rolled steel. Rotary straighteners are used for high-accuracy straightening. They are also used for eliminating ovality in the transverse cross section of tubes when the tubes cannot rotate about their axes. Coiled tubes are processed, for example, by rotary straighteners. Skewed straighteners straighten the edges of tubes and of rounded cross sections. They have one or several bands consisting of two or three rolls. The use of triple-roll bands allows for the straightening of tubes with thin walls and provides good quality surfaces. Revolving-arbor straighteners remove twisting in tubes that are not round. Axial stretching is added to straighten items with uniform cross section, and machines for such cases are called rotary straighteners. Stretch straighteners are used for straightening thin sheets and bands. Straightening presses are used mainly for straightening large sized rolled steel, rails, and large tubes.

Figure 1. Schematic of the arrangement of rolls in a straightener