Conduit bending

Offset — two equal bends that move the run over by the rise. The distance between the bends is the rise times the multiplier, which is the cosecant of the angle (2 for 30°, 1.414 for 45°). The run also gets shorter: the shrink, tan(θ/2) per inch of rise (¼″ per inch at 30°). Give the distance from the end to the obstruction and the tool adds the shrink so the offset lands where it should. Tick trade-rounded multipliers to use the pocket-card figures (6, 2.6, 2, 1.4, 1.2 and 1/16, 3/16, ¼, ⅜, ½) instead of exact trigonometry.

Rolling offset — the run has to move up and sideways. Bend an ordinary offset for the true offset, √(rise² + roll²), in a plane tilted toward the roll; the tool gives the tilt and an end view.

3-point saddle — a 45° centre bend with a 22.5° bend each side, for crossing a pipe. The sides are 2.6 × the height from the centre (2½ × on the trade cards) and the centre mark moves out by 3/16″ per inch of height. 4-point saddle — two offsets with the obstruction’s width between them.

90° stub — stub height minus the bender’s take-up (deduct). Choose EMT, rigid or IMC and the trade size; the take-up and radius come from the Bender data tab, where you can enter the numbers stamped on your own bender. Back-to-back 90s gives the second mark (star on the mark, measured from the back of the first 90) and the cut length, using the gain of each bend.

Kick — one bend to move the conduit over; solve for the angle or the distance. Segment 90 — a large-radius 90° made of many small shots: degrees per shot, spacing, and a mark table from the end. Parallel offsets — several conduits offset together: each one farther out moves its marks by spacing × tan(θ/2) so the spacing stays even through the bends.

360° rule — add bends from any tab (or quickly with the buttons) and the total is checked against the limit for the raceway: 358.26 for EMT, 344.26 rigid, 342.26 IMC, 352.26 PVC and so on — no more than 360° between pull points.

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Offsets and saddles are treated as sharp bends at the marks, which is where the trade multipliers and shrink figures come from. 90s use the bender’s centreline radius: the gain of a 90 is 2(R + OD/2) − πR/2, the difference between the two legs measured to the back of the bend and the length of conduit actually used. Segment shots are placed on a polygon whose sides touch the bend radius, so shot spacing is 2R·tan(45°/n). Outside diameters are from NEC Chapter 9, Table 4. The take-up and radius figures are typical hand-bender and one-shot shoe values — makers differ, so check yours.

For wire sizes and voltage drop see the wire size calculator; how many wires fit is in conduit fill and box fill. Other field tools: available fault current, transformers and three-phase and the electrician’s quick reference.

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