Q: What is the secret of bending rebars in the fabricating shop so that the radius is always correct and the bars are not twisted?
According to John R. Deubert, vice president of the Fabrication Division of Pacific States Steel Corporation, it is a matter of how the bars are fed through the radius-bending equipment.Bars should not be radius-bent along the longitudinal rib as shown in Figure 1. On the other hand, if the bars are allowed to ride on the bottom rib as they pass through the radius bender, as in Figure 2, the resulting radii may vary slightly for every bar. This method may also cause the bars to rise up or twist beyond a single plane as they leave the radius bender.
However, if the longitudinal ribs are tilted from the vertical position as shown in Figure 3 all bars are bent to a uniform radius in one plane. Each rib should just barely make contact with the drivers when the bar is fed into the radius bender. Once the bar starts to pass through the drivers no further adjustment is necessary.It should be pointed out that the bar position in Figure 3 will result in a radius bend toward the left side of the radius bender.If the longitudinal ribs of a bar happen to be slightly twisted the operator must note the amount of twist on the entire length of the straight bar prior to feeding into the radius bender. He should then vary the position of the bar somewhat from that in Figure 3, depending on the amount of twist. He must make certain, however, that the longitudinal ribs on the tail end of the bar are positioned as shown in Figure 3 when they leave the drivers.The grooves of both drivers must, of course, be equally well maintained at all times.