Three-point saddle calculator

A three-point saddle carries a run over a round obstruction with one centre bend and two outer bends half its angle. Enter the depth you need to clear and the centre angle; the calculator gives the distance from the centre mark to each outer mark, and the shrink to add so the far end still lands right.

Worked example

Say a two-inch conduit crosses your run and you need a 2 inch saddle over it at a 45° centre. The outer bends are 22.5°, whose multiplier is 2.613, so each outer mark sits 5 1/4 inches from the centre mark (2 × 2.613 = 5.23). The shrink is the 22.5° figure applied to the depth, about 2 × 0.199 ≈ 3/8 inch. Mark the crown of the obstruction, measure 5 1/4 inches each way for the outers, bend the centre 45° first, then each outer 22.5° the opposite way.

The formula

The outer bends are half the centre angle, and the mark spacing is the depth times the outer multiplier:

outer angle = centre ÷ 2 · centre-to-outer = depth ÷ sin(outer)

Each half of the saddle is just an offset raising the pipe by the depth at the outer angle, so it obeys the same rise ÷ sin θ the offset does. The two halves meet at the centre bend over the crown. Shrink is depth × (1/sin(outer) − 1/tan(outer)), the offset shrink at the outer angle.

Centre angle and its outers

The centre angle you pick sets the outer angle and therefore the mark spacing. A shallower centre spreads the saddle out and reduces shrink; a steeper one keeps it compact but pulls the end back harder.

Questions

What angle is a three-point saddle bent at?

The centre bend is the one you choose — 45° is the classic. The two outer bends are always half the centre, so a 45° saddle has 22.5° outers and a 60° saddle has 30° outers. The calculator uses the outer angle to work the mark spacing, because that is the geometry that clears the pipe.

Where does the centre mark go?

On the crown of the obstruction — line the centre of your saddle up with the centre of what you are going over. Then measure the centre-to-outer distance each way from that mark and bend the outers there. Bend the centre first, then the two outers, so the centre stays put.

Does a saddle shrink the pipe?

Yes. A three-point saddle pulls the end back the same way an offset does, and by the outer-bend shrink applied to the depth. Add the shrink figure to the measurement that locates your centre mark, or the far end lands short.

Three-point or four-point saddle?

A three-point saddle goes over something round — a pipe or a conduit crossing yours. A four-point saddle is two offsets with a flat run between them, for going over something with a flat top like a beam or a duct. Use the four-point calculator for the flat case.

Related tools

• Four-point saddle calculator — for a flat-topped obstruction.
• Conduit offset calculator — the two-bend jog a saddle is built from.
• Conduit bending multipliers — every angle, exact and rounded.