Figure 5-47.Bender degree markings.
To make accurate offsets of 2 inches or more in
depth, you can mark a predetermined distance on the
conduit. The distance between the bends depends on
the depth of the offset and the amount of bend that you
are going to use. Table 5-3 shows the formula to use to
find the distance to be marked on the conduit. It also
shows the constant multiplier that must be used in the
formula for the angle of bends you intend to use and the
shrinkage per inch.
Let us use an example to see how the formula
works. Suppose you need to avoid a part of a
obstruction that requires an 8-inch offset, you are going
to use 30-degree bends, and you are 40 inches from the
obstruction. Table 5-3 shows that the constant
multiplier for 30-degree bends is 2 and the shrinkage of
one-fourth inch equals 2 inches for a total of 42 inches.
Using the formula, multiply the depth of the offset (8
inches) times the constant multiplier (2), and the result
is the distance needed between the bends (16 inches).
You place the first mark at 42 inches, the second 16
inches apart, and using the arrow of the bender, make a
30-degree bend on the same side of each mark, as shown
in figure 5-46. In this example, a 30-degree bend gives
us the offset we need. If you make both bends inside the
marks, you will end up with much less than the desired
offset. If you make both bends outside the marks, you
will have too much offset. The amount of bend, in this
case 30-degree at each mark, is obtained by using the
degree markings on the bender, as shown in figure 5-47.
Notice that the side of the conduit closest to the bender
is in line with the 30-degree marking on the bender. If
you have a bender without markings, a protractor
(works especially well on larger conduit) can be used or
you can lay a 30-degree angle out on a large piece of
paper or on the floor with chalk. Then check the bend
against the 30-degree angle you have laid out.
Normally, offsets are made by making the first bend on
the floor and the second bend in the air, as shown in
Figure 5-48.Bending on the floor and in the air.