Conduit Bending Glossary

The outside of a finished 90. Stub and leg lengths are measured from the end of the conduit to the back of the 90, the deduct runs from the bender’s arrow to it, and the star on many hand benders shows where it will fall.

Two 90s in one conduit, bent in the same plane so their legs are parallel and a set distance apart, measured from the back of one 90 to the back of the other. Mark that distance from the back of the first 90 and bend the second with the mark on the bender’s star.

The marks on a bender head that conduit marks line up with. The arrow is where the deduct is measured to, used for stubs, offsets and a saddle’s outer bends; the star shows the back of a 90; a rim notch or teardrop marks a bend’s center, usually 45°. Power benders use a benchmark, often the hook’s front edge.

The volume an electrical box needs for what is inside it, under NEC 314.16. Each conductor counts an allowance for its size, 2 in³ for 14 AWG and 2.25 in³ for 12 AWG; clamps, support fittings and grounds add allowances, and each device yoke counts double. The total must fit the volume marked on the box.

The field name for four bends that carry conduit up over a box or beam and back down: an offset up, a straight as wide as the obstruction, and a matching offset down, the same shape as a 4-point saddle. It also means the single short offset that steps conduit off a wall into a box.

The radius of a bend measured to the center of the conduit, not its inside or outside. Each shoe has its own for each trade size and conduit type, and it sets the deduct, the gain and the spacing of every mark: 4 3/16" on a typical 1/2" EMT hand bender.

90s nested like rings, so a rack of conduits turns a corner with the same gap all the way round. Each conduit outside the first bends on a radius larger by its center-to-center distance from the first, so its sweep is longer by π ÷ 2 (about 1.57) times that distance and its marks sit farther apart.

How much of a conduit’s inside area its wires take up. NEC Chapter 9 Table 1 allows 53% for one wire, 31% for two and 40% for three or more, with the areas from Tables 4 and 5, so 1/2" EMT holds 9 THHN wires of 12 AWG.

The length of straight conduit to cut so the bent piece comes out right. For one 90 it is the stub plus the other leg, less the gain: a 12" stub and a 36" leg on a typical 1/2" EMT hand bender cut at 45 1/2". Each offset or saddle in the run adds its shrink.

How much of a stub the bender uses up in a 90: the distance from the arrow, or a power bender’s benchmark, to the back of the finished bend. Subtract it from the stub length to find the mark. Most hand benders deduct 5" for 1/2" EMT, 6" for 3/4" and 8" for 1".

The conduit a bend itself uses, measured along its centerline from where the bend starts to where it ends: the centerline radius times the angle in radians, or about 1.571 times the radius for a 90. That is 6 9/16" on a typical 1/2" EMT hand bender.

A twist between bends that should lie in one plane, usually because the conduit was rolled more or less than half a turn between the bends of an offset or saddle. The ends no longer line up and the conduit won’t lie flat; twisting it back into plane at a bend fixes it.

Electrical metallic tubing: thin-wall steel or aluminum conduit, joined with set-screw or compression fittings instead of threads (NEC Article 358). It is the conduit most often bent by hand, up to 1-1/4" on a hand bender. Up to 2" it is slimmer than rigid of the same trade size: 0.706" across for 1/2".

Four bends that carry conduit over something wide, like a beam or a duct: an offset up, a level straight across the top as long as the obstruction is wide, and a mirror-image offset back down. All four bends use the same angle, and the saddle shrinks the run by twice as much as one offset.

The conduit a bend saves by going round its arc instead of out to a sharp corner: two setbacks minus the developed length. For a 90 it is counted to the back of both legs, 2 1/2" on a typical 1/2" EMT hand bender, and the cut length is the stub plus the other leg minus the gain.

A hand bending tool for small rigid conduit and IMC: a short open jaw on a pipe handle that bends the conduit a little at a time instead of round a shoe, handy for stubs out of a slab. In NEC 314.16(B)(3), a hickey is also a threaded fitting that hangs a luminaire from a box, and it counts toward box fill.

Intermediate metal conduit: threaded steel conduit with a thinner wall than rigid, so it is lighter and a little roomier inside (NEC Article 342). Its outside diameter is just under rigid’s, 0.815" against 0.840" at 1/2", and it bends on rigid/IMC shoes, often the same ones as rigid.

A single shallow bend in the leg of a 90, made at right angles to the 90’s own bend, that moves the stub sideways. It lets a run that sits out from a wall still turn up tight against it, or step over into a box.

A straight part of a bent conduit on one side of a bend. A 90 has two, the stub and the other leg, each measured from its end of the conduit to the back of the 90, and their sum less the gain is the cut length.

The number an offset’s height is multiplied by to give the distance between its two bends: 1 ÷ the sine of the bend angle (the cosecant). It is 2.000 at 30° and 1.414 at 45°, and many hand benders show the rounded figures beside their angle marks.

Two bends of the same angle that move a conduit over by a set distance and carry it on parallel to its first line, to clear a beam, a box or a pipe, or to step off a wall. The bends are the offset height times the multiplier apart, and the run comes up short by the shrink.

A bender whose shoe makes a whole bend, up to a full 90, in one pass instead of a series of small segment bends: mostly hydraulic benders for large conduit, especially push-type ones. NEC Chapter 9 Table 2 allows one-shot and full-shoe bends a tighter radius than other bends, 9 1/2" instead of 12" for 2".

Matching offsets in conduits that run side by side, bent so the bank keeps its spacing through the bends. Each conduit gets the same offset, but its marks move along from its neighbor’s by the center-to-center spacing times the angle’s shrink per inch, 0.268 at 30°.

A place where wire can be pulled from, such as a box, a pull box or a conduit body like an LB. The NEC allows no more than the equivalent of four quarter bends, 360° in all, between two pull points: 358.26 for EMT, 344.26 for rigid, 342.26 for IMC and 352.26 for PVC.

Rigid PVC conduit, Schedule 40 or the thicker-walled Schedule 80 (NEC Article 352). It isn’t bent on a shoe: it is heated in a hot box or a heating blanket until it softens, formed, and held until it cools, and factory elbows are common too. Offsets and saddles follow the same math as metal conduit.

A 90° bend, the unit the NEC counts bends in: no more than four quarter bends, 360° in all, between pull points. Every bend counts by its angle, so a 30° offset adds 60° and a 3-point saddle with a 45° center adds 90°.

A run of conduits side by side, on strut or a trapeze hanger, that bend together and keep their spacing. Bends square to the rack are the same in every conduit. Bends in the rack’s own plane, like turning a corner along a wall, move each conduit’s marks, and its 90s become concentric bends.

Rigid metal conduit (RMC): the heaviest metal conduit, thick-wall threaded pipe, usually galvanized steel (NEC Article 344). It needs more force than EMT and rigid/IMC shoes with a bigger radius, and it springs back more. At 1/2" its outside diameter is 0.840", against 0.706" for EMT.

In a rolling offset, how far the conduit has to move up or down, measured center to center; the roll is how far it moves sideways. Together they give the true offset to bend, √(rise² + roll²). More loosely, rise is the height of any offset or saddle.

In a rolling offset, how far the conduit has to move sideways, measured center to center, while the rise is how far it moves up or down. To roll a conduit is also to turn it in the bender, like the half turn between the two bends of an offset.

An offset that moves the conduit up and sideways at once. It is bent as one ordinary offset along the diagonal, the true offset √(rise² + roll²), then rolled so its bends lean out of plumb by atan(roll ÷ rise): a 6" rise and an 8" roll make a 10" offset.

A 90 built from several small bends, called shots, spaced evenly along a sweep to give a much bigger radius than the shoe’s. Each shot is the total angle divided by the number of shots, such as six shots of 15°, and more shots make a smoother sweep.

The distance from the start of a bend to the corner where its two straight legs would meet if carried on: the centerline radius × tan(angle ÷ 2), so for a 90 it equals the radius. Some bender charts use the word for the deduct instead.

The curved, grooved part of a bender that the conduit is pulled round, which sets the radius of the bend. A hand bender’s head is its shoe; power benders take a shoe for each trade size and conduit type, or a combo shoe with several grooves. Each shoe has its own centerline radius and deduct.

How much shorter an offset or saddle leaves the run, because the conduit travels the slope between the bends instead of the straight line it replaces. Per inch of offset height it is tan(angle ÷ 2): 0.268" at 30° (about 1/4") and 0.414" at 45°. Allow for it in cut lengths and in marks past the offset.

The degree or two a bend opens up when the bender lets go, as the metal relaxes. Rigid and IMC spring back more than EMT, so bend slightly past the angle and check it with a level or an angle finder once the conduit is out of the bender.

A single 90 that turns conduit up a wall or out of a floor, with its end at a set height. The stub length runs from the end of the conduit to the back of the 90; take off the bender’s deduct to find the mark, and bend on the arrow with the hook toward the end.

A wide, gentle bend, usually a 90 with a much bigger radius than a hand bender’s shoe, for large conduit, long wire pulls and racks turning a corner. Sweeps come from big power-bender shoes, from factory elbows, or from a segmented 90 bent in shots.

Three bends that carry conduit over something small and round, like another pipe: a center bend lifts it over the top, and two outer bends of half that angle bring it back to its line. A 45° center with 22.5° outer bends is usual; the center bend goes on the notch and the outer ones on the arrow.

The name of a conduit size, like 1/2" or 3/4", rather than a measurement of it. 1/2" EMT is 0.706" across the outside and 1/2" rigid 0.840", so shoes, deducts and fill tables go by trade size and conduit type together. The NEC pairs each trade size with a metric designator, 16 for 1/2".

The voltage lost along a circuit’s wires to their resistance, which grows with the length of the run and the current. NEC informational notes suggest no more than 3% on a branch circuit and 5% with the feeder; a 16 A load 100 ft away on 12 AWG copper at 120 V loses 6.32 V, or 5.3%.