How to Bend a Rolling Offset in Conduit
Quick answer
A rolling offset moves conduit two ways at once, up and over, with one offset bent along the diagonal and rolled out of plumb. True offset = √(rise² + roll²); roll the bends atan(roll ÷ rise) from plumb. A 6" rise with an 8" roll is a 10" offset rolled 53.13°. Mark and bend it as an ordinary offset of the true offset height.
A rolling offset moves the conduit two ways at once, say up 6" and over 8" to reach a box that isn’t straight above or beside the run. Instead of two offsets, bend one offset along the diagonal and roll it over so its bends lean out of plumb.
What to measure
- Rise: how far the conduit has to move up or down, center to center.
- Roll: how far it has to move sideways, center to center.
- Angle: both bends are bent to it, as on a plain offset.
- Distance to obstruction (optional): from the end of the conduit, with the offset finished there or starting there, as on the Offset screen.
How to bend it
- Enter the rise, roll and angle. The calculator gives the True offset, the diagonal the conduit actually travels, and the marks for an offset of that height.
- Mark and bend it exactly like an offset: first mark on the arrow with the hook facing the end, then roll the conduit half a turn and bend the second mark to the same angle.
- Hold the conduit in place and turn it on its own axis until the bends lean out of plumb by the Roll bends angle, toward the side it has to move.
- Check that the far leg sits at the right height and the right distance over before you fasten it.
Where the numbers come from
true offset = √(rise² + roll²)roll bends = atan(roll ÷ rise)From there it is an ordinary offset of the true offset height, with the same allowance for the shoe’s radius as the Offset screen.
- Rise
- 6"
- Roll
- 8"
- Angle
- 30°
- True offset
- 10"
- Roll bends
- 53.13°
- Between bends
- 19 15/16" (20" by multiplier)
- Shrink
- 2 9/16" (2 11/16" by multiplier)
If it turns orange or red
The colors are the Offset screen’s, for the true offset. Red means the two bends would run into each other, and orange that there is too little straight between them for the shoe to grip. Use a smaller angle.
Get the marks for your bender
BendMate works this out from your bender’s radius and deduct, flags a bend that won’t work, and shows you every mark.
Common questions
How do you calculate a rolling offset?
Find the true offset with Pythagoras, √(rise² + roll²), then bend an ordinary offset of that height. At 30°, a 10" true offset needs 20" between bends by the multiplier method, or 19 15/16" on a 1/2" EMT hand bender.
How far do you roll the conduit on a rolling offset?
Turn the bent conduit on its own axis until the bends lean out of plumb by atan(roll ÷ rise), toward the side it has to move. For a 6" rise and an 8" roll that is 53.13°.
What is the shrink on a rolling offset?
It is the shrink of an ordinary offset of the true offset height. A 10" true offset at 30° shrinks 2 11/16" by the multiplier method, or 2 9/16" on a 1/2" EMT hand bender, which allows for the shoe’s radius.