Cómo doblar conduit
Bending conduit is one idea repeated: read a number off the job, turn it into a mark on the pipe with a bit of trigonometry, and pull the same angle every time. This is the order the bends tend to come in as you learn them, each as a procedure you can follow at the bender, and the calculator that does the arithmetic for each. None of it is a code question — it is all geometry, and a wrong number costs a stick of pipe, not a life. If you have never held a bender at all, start with the six lessons on Bending, from zero and come back.
Before anything: read the bender
Every hand bender has the same set of references cast into the shoe, and they are what every layout mark on this site lines up with.
- Arrow — your pencil mark for a stub-up, and for the bends of an offset, sits under the arrow.
- Star (or a line on the back of the shoe) — the back of a finished 90 lands here. It places the second bend of a back-to-back.
- Notch — on most shoes, where the centre of a saddle lands. Some makers mark it as a teardrop or a line; check yours.
- Degree marks — the angle pulled so far, read where the pipe crosses them.
- Take-up — a figure stamped on the shoe for each pipe size: the length the 90 sweep eats. It belongs to that tool. There is no universal chart, so read it or derive it; one test bend on the bender take-up page gives it back if it has worn off, and you can save yours there so the stub-up tools fill it in.
The pull
The bender works by pressing the pipe into the curve of the shoe while the handle turns it. The pressing is your foot; the turning is your hands. Get that order wrong and the pipe comes out kinked, flattened or short of the angle.
- Pipe on the floor, hook over it. The hook goes over the pipe at the front of the shoe, the free end (the one that will stand up) pointing away from you. Lay the arrow on your mark.
- Foot on the pedal, weight on it. Most of the work is your foot. It keeps the pipe seated in the groove of the shoe the whole way round. If the pipe lifts out of the groove it will fold.
- Steady pull on the handle. One continuous motion, no jerking. Watch the degree marks, not the floor: the angle is read where the pipe crosses the shoe.
- Go a touch past. Every pipe relaxes open a little when you let go — springback. A degree or two past the mark and it settles on it. How much is a feel you get from the first few scraps.
- Check against something square. A 90 stands against a wall; an offset lies flat on the floor with no rock. Fix it now, before the next bend depends on it.
The 90° stub-up
Start here. You want a leg of a set height, so mark height − take-up from the end, line the arrow up with the mark, and bend to 90°. When your stubs land on the mark every time, the bender and the take-up are working, and everything else on this page will land too. The stub-up calculator does the subtraction and shows the mark on the pipe.
- Measure. Decide the finished height, to the back of the 90 (the outside of the bend). Read the take-up stamped on the shoe for this pipe size.
- Mark. From the free end, measure height − take-up and put a pencil line all the way round the pipe, so you can see it from the bender.
- Line up. Hook the pipe with the free end away from you. Slide the bender along until the arrow sits on the line.
- Bend. Foot on the pedal, steady pull to the 90 mark, then a touch more for springback.
- Check. Stand it up and measure to the back of the bend. Tall or short by the same amount every time? Your take-up figure is off by that amount — fix the figure, not the method.
The offset — the workhorse
An offset is a pair of matching bends that jog a run past an obstacle and bring it back level. Pick an angle, multiply the rise by the multiplier for the distance between the marks, and add the shrink to your measurement so the far end still reaches. This is the bend you make most; the offset calculator and the shrink calculator cover it, and the multiplier reference lists every angle. A tiny version, the box offset, seats a connector into a knockout.
- Measure. The rise: centre of the pipe where it runs now to centre of where it must end up. And the layout measurement: from the end of the pipe to where the offset should begin.
- Mark. Mark 1 goes on the layout measurement — the pipe before it is straight and loses nothing. Mark 2 goes the multiplied distance further along (rise × multiplier). Lines all the way round. The shrink goes on the overall length instead: the jog pulls the far end back by it.
- Line up. Arrow on mark 1, free end away from you.
- Bend. Pull to the angle. Take the pipe out, turn it over end for end so the second bend goes the opposite way, arrow on mark 2, and pull the same angle. Sight down the pipe: both bends must be in the same plane or the run will roll.
- Check. Lay it flat. It should sit on both flats without rocking, and the step should measure the rise. If the far end is short, you forgot the shrink — the calculator's "Do it" list puts it in the first line so you cannot.
Saddles — going over something
To cross an obstruction rather than step past it, you saddle over it. A three-point saddle peaks to a centre bend over a round pipe; a four-point saddle uses two offsets and a flat top for a beam or duct. Both are offsets in disguise, so the same multiplier and shrink turn up again.
- Measure. From the end of the pipe to a point over the crown of the obstruction: the centre measurement. And the depth: how far the run must lift to clear.
- Mark. Centre mark at measurement + shrink. Outer marks the centre-to-outer distance each side of it (depth × the multiplier for the outer angle, which is half the centre).
- Line up. Centre mark on the notch (or the arrow, if your shoe says so).
- Bend. Centre first, to the centre angle. Then flip the pipe, arrow on each outer mark in turn, and pull the outer angle the opposite way. Centre first, always — bend the outers first and the crown wanders off the mark.
- Check. Both flats sit on the floor and the crown clears the obstruction by what you asked for. A Z instead of a hump means one outer went the same way as the centre.
Two 90s and a kick
Set two 90s a fixed distance apart and you have a back-to-back bend, a squared U — the first 90 is an ordinary stub, the second is bent off the star so the distance between the backs lands true. Add a single bend in the tail of a stub to lift it past something low and you have a kick 90; the kick is one leg of an offset, so it uses the offset multiplier on its own rise.
- Measure. The first leg height and the distance between the two backs.
- Mark. First mark at height − take-up from the end, as a stub. Second mark that distance further along.
- Line up. Arrow on the first mark for the first 90. For the second, the star on the second mark — you are locating the back of that bend, not its start.
- Bend. Both 90s the same way, so the legs stand parallel.
- Check. Measure back to back. If it is off — and off by the same amount on every stick — you used the arrow on the second mark instead of the star.
When the offset is not in one plane
If a run has to rise and move sideways at once, it is a rolled offset: work the true offset from the rise and roll, roll the pipe to the roll angle, then bend it as an ordinary offset. The trigonometry is the same triangle, one dimension up. The only new step is the roll: put a pencil line along the pipe, and before the first bend rotate the pipe in the shoe by the roll angle so the line leans over that far. Both bends in the same rolled plane, or the jog ends up pointing somewhere else.
Big sweeps and groups
A radius too wide for one pull becomes a segmented bend — many small bends spaced along the pipe, each pulled to the same small angle on its own mark; the developed length is how much pipe the sweep consumes. Run several conduits through the same corner and you keep them even with concentric bends, each on a larger radius than the last, where the gain per run tells you how the lengths differ. Step a whole rack over together with parallel offsets: each pipe's marks start a stagger further along than the one beside it, and the stagger constant is the shrink constant.
The whole reference
Every formula behind these is written out on the formulas page, with the one triangle they all come from, and the words — shrink, gain, take-up, developed length, springback — are defined in the glossary. Reading the results back off a tape is on tape measure fractions.
Preguntas
- What is the first bend to learn?
- The 90° stub-up. It teaches you to read the bender, to trust the take-up figure, and to measure a mark from the end — the habits every other bend builds on. Get a stub landing on the mark every time before you move to offsets.
- Why does my bend keep coming out at the wrong height or short?
- Two usual causes. Wrong height on a 90 means the take-up figure is off for your bender — derive it from a test bend. A run finishing short means you forgot shrink on an offset or saddle. Add the shrink to your measurement before the first mark.
- Do I bend EMT and rigid the same way?
- The geometry is identical — an angle is an angle. What changes is take-up and gain, which grow with the pipe’s radius, and the effort. Use the figure stamped on the bender for the pipe you are actually bending, and the same multipliers and shrink apply.
- Why does the pipe kink instead of bending?
- Because the force went into the handle and not the pedal. The shoe has to be pressed onto the pipe by your foot while the handle turns it; pull the handle alone and the pipe lifts out of the groove and folds. Foot pressure down, steady pull, no jerking.