How to Bend Rigid and IMC Conduit

How rigid and IMC differ from EMT

Rigid (RMC) is thick-walled threaded pipe. IMC is a lighter threaded cousin. Both are stiff and strong, so they need more force than EMT, and at the same trade size they are fatter, which means a bigger shoe and a bigger radius.

That is why a bender made for EMT does not fit rigid. Use the head for rigid or IMC, and the take-up that goes with it.

Which bender to use

• Hand benders with rigid/IMC heads take the smaller sizes.
• Mechanical (Chicago) benders take rigid and IMC up to about 1-1/2".
• Electric benders take 1/2" to 2" with the right shoe.
• Hydraulic benders take the large sizes, from 2-1/2" up, and heavy rigid.

Many benders use the same shoe for IMC and rigid. Check the shoe, because some sizes of each need their own.

Marking and bending rigid

1. Find the take-up for your shoe and rigid, not the EMT number. It is cast on a hand head or printed in a power bender’s chart.
2. Measure and mark as you would for EMT. A 90 is the stub minus the take-up.
3. On a power bender, line the mark up with the benchmark the manual names, often the front edge of the hook. Leave the minimum length of conduit past the mark that the manual asks for.
4. Support the free end. Rigid is heavy, and a sagging length twists in the shoe.
5. Bend to the angle, then check it with a level. Expect to go slightly past, because rigid springs back more than EMT.

Cutting and threading

Rigid and IMC are threaded rather than clamped, so the cut length matters. Work it out from the finished bends, then cut and thread. For a single 90 it is:

Cutting and threading after the bends is the safe order. If you thread first, keep the threaded end clear of the hook and the shoe so the threads are not damaged, and leave the manual’s minimum length past the mark.

Habits for heavy conduit

• Bend a scrap piece first and keep it. It shows how far past the angle you need to go, and you can measure it.
• Mark with a marker rather than a pencil on dirty or oily pipe, and mark before you load it.
• Wear gloves and keep your feet clear. Heavy pipe swings when the bend finishes.
• Lay the finished bend against the run before it goes up, since heavy pipe is hard to adjust once it is installed.

A worked example

On a real rigid shoe the figures come out a little smaller than the chart’s, because the larger radius cuts each corner more. That is why a bender’s own numbers matter more as the size grows. BendMate includes rigid and IMC shoes for the benders that take them.