Lo básico del doblado de conduit

A hand bender is a curved shoe on a handle; you hook it on the pipe, put your foot on the shoe and pull the handle, and the pipe takes the shoe's radius. Everything else — the marks, the take-up, the multipliers — is bookkeeping so the bend lands where you wanted it. This page explains the tool and the three bends everyone learns first, in words. The arithmetic behind them is trigonometry, and bentright works it for you when you are at the bender.

The bender and its marks

The shoe is the curved block; its radius is the radius every bend gets. The hook grips the pipe so it cannot slide as you pull. The foot pedal is where your weight goes, and the handle is the lever. On the shoe are the marks: an arrow you line up with your pencil mark for a stub-up and for each bend of an offset; a star (or a similar back-of-bend mark) that shows where the back of a 90° lands, used for back-to-back bends; and a notch or line on the rim that marks the centre of the shoe, used for the middle bend of a saddle. The take-up — the deduction for a 90° — is stamped on the tool for that size of pipe. Every maker lays this out a little differently. Read your bender.

The three bends everyone learns first

The 90° stub-up. One bend that turns the pipe straight up from the floor to a set height. You measure the height you want, subtract the bender's take-up, mark the pipe there, put the arrow on the mark, and pull to 90°. The take-up exists because the bend has a radius: the pipe starts curving before the mark, and the tool has already accounted for that. The glossary has the word; the stub-up calculator on bentright does the subtraction and checks your level.

The offset. Two equal bends in opposite directions that move the pipe sideways to clear an obstacle or line up with a box, and leave it running parallel to where it started. The distance between the two marks is the offset depth times a multiplier for the angle you chose. The multiplier is trigonometry — one over the sine of the angle — and that is the only sentence of theory you need: the common values fit on the multipliers sheet, the offset drill makes the multiplication automatic, and the offset calculator on bentright gives you both marks with the shrink already added. Shrink is the length the offset "eats" — the diagonal uses more pipe than the straight run it replaces — so the whole run comes up short by a bit for every inch of offset unless you add it back. Shrink and gain are both in the glossary.

The three-point saddle. Three bends: a centre bend that lifts the pipe over a small obstruction — a pipe crossing your run — and two smaller bends either side that bring it back down. The centre mark goes on the rim notch, the outer marks on the arrow, and the outer bends are made in the opposite direction to the centre one. Like an offset it has a shrink, and like an offset the marks are a multiplication; bentright's saddle calculator does it with the marks laid out.

The habits that make it come out straight

Bender on the floor, foot on the pedal. Your weight makes the bend, not your arms; pulling with the handle alone kinks the pipe at the hook. Keep steady pressure through the pull and let the shoe form the curve.

Keep it level. A torpedo level on the pipe, or the bubble built into the handle, tells you when a stub-up has reached 90°. For an offset, the angle you bent to is the angle the multiplier assumed — bend to 30° with a 30° multiplier, or the marks are wrong.

Keep the bends in one plane. The second bend of an offset has to be in exactly the same plane as the first, or the pipe wanders off sideways — a dog leg. Before you make the second bend, sight down the pipe from the end like a rifle barrel and roll it until the first bend is dead in line with the shoe. Then pull.

Over-bend a touch. Steel springs back a few degrees when you let go. Pull slightly past your angle, release, and check — after a few bends you will know how much your pipe and your bender give. The word is springback, and how much depends on the material and the size.

Measure twice, bend once, check before the next one. A stub that is an inch short is scrap; an offset made before you checked the first bend's angle is scrap twice. Bend, check with the level and the tape, then mark the next.

EMT and rigid

A hand bender is an EMT tool — the thin-wall tube bends cold with your weight. Rigid, the thick-wall threaded pipe, takes more force: small sizes can be bent with a hickey (a hook with no shoe, working the bend up a bit at a time) or a hand bender built for rigid, and larger sizes go on a mechanical or hydraulic bender. Names only here. Which raceway may be bent how, how many bends a run may have between pull points, and the minimum radius are all code — your book has them, and your bender's shoe radius is one of the things the book is checking.

En la obra

Preguntas frecuentes

Ver también

• bentright — bending from zero — six illustrated lessons at the bender, then the calculators.
• Bending multipliers & shrink — the pocket sheet for the common angles.
• Offset math practice — drill the multiplication until it is automatic.
• Right triangles on the job — where the multiplier comes from, if you want it.
• Glossary: shrink — and take-up, gain, kick, dog leg beside it.