Calculating Shrink - Greenlee 777 Instruction Manual

Laying Out Offset Bends
Calculating "Shrink"
When making offsets, it is common practice to make
the offset as close to the obstruction as possible. When
laying out an offset and working away from an obstruc-
tion, no special provisions are required. However, when
approaching an obstruction, the conduit "shrinks."
CENTER-TO-CENTER DISTANCE
To get the second bend closer to the obstruction, both
bends must be adjusted forward. The amount of this ad-
justment is referred to as shrink. The following illustration
shows the same installation with shrink factored in.
Bending marks have been moved forward
Second bend is closer to the obstruction
Greenlee Tools, Inc.
To find the center-to-center distance and the amount of
shrink per inch of depth for a particular offset, consult
the Greenlee Offset Multiplier and Shrink Table.
Greenlee Offset Multiplier and Shrink Table
To use this table: Determine the depth of the offset
and the degree of bend. Calculate the center-to-center
distance by multiplying the amount of the offset by the
multiplier (center column). Calculate the amount of shrink
by multiplying the shrink per inch of offset depth (right-
most column) by the offset depth.
SHRINK
9
777 Segment Bender
OFFSET ANGLE MULTIPLIER
10˚ 6.0
15˚ 3.86
22-1/2˚ 2.6
30˚ 2.0
45˚ 1.4
60˚ 1.2
Example:
Multiplier for 30°:
Multiply the amount of
offset by the multiplier to
find the center-to-center
distance:
Find the amount of shrink
per inch of offset in the table: 1/4"
Multiply the shrink per inch
by the amount of the offset:
Mark the conduit:
4455 Boeing Dr., Rockford, IL 61109 815-397-7070
SHRINK PER INCH OF
OFFSET DEPTH
1/16"
1/8"
3/16"
1/4"
3/8"
1/2"
6-inch offset
30-degree bend
2
2 x 6 = 12
6 x 1/4" = 1.5 inches
Place the second bending
mark 1.5 inches past the
obstruction; measure back
toward the starting point
and place the first bending
mark 12 inches before the
second bending mark.