BACK-TO-BACK BENDS.- The back-to-back bend is actually two adjacent 90s made in the same piece of conduit. You make the first 90 with the amount
Figure 5-43.- Right-angle bend, 90.
Figure 5-44.- Using the star for back-to-back bend.
Figure 5-45.- Box offset. of stub you need, as described previously. To determine where to place the next stub, you first need an outside-to- outside measurement. This measurement is the distance from the back of the first bend to the point where you want the back of the second bend.
Two methods are used for making the second bend. The first is to subtract the take-up, use the arrow on the bender, and pull the bend in the same direction as you did the first bend. The second method, and probably the
easiest, is to turn the bender around, line up the star on the bender with your outside-to-outside measurement, and pull the bend in the opposite direction, as shown in
Table 5-3.- Offset Bending Formula
FORMULAAND CONSTANT MULTIPLIER FOR DETERMINING DISTANCE BETWEEN BENDS WHEN BENDING OFFSETS
FORMULA OFFSET CONSTANT DISTANCE DEPTH MULTIPLIER = BETWEEN BENDS
ANGLE OF CONSTANT BENDS MULTIPLIER SHRINKAGE
22 1/ 2° x 22 1/ 2° 2.6 3/ 16" PER INCH 30° x 30° 2.0 1/ 4" PER INCH 45° x 45° 1.5
60° x 60° 1.2 3/ 8" PER INCH 1/ 2" PER INCH