How to Bend a 3-Point Saddle
A 3-point saddle uses a 45° center bend and two 22.5° outer bends. Put the center mark at the obstruction's center line plus 3/16" of shrink per inch of height, then put an outer mark 2.5 × the height on each side of it. For a 4" pipe in the way: outer marks 10" from the center, and add 3/4" to the center measurement.
The numbers
outer marks = height × 2.5 (each side of the center)
shrink to the center mark = height × 3/16"
| Height | Center to each outer mark | Add to center mark | Total shrink of the run |
|---|---|---|---|
| 1" | 2 1/2" | 3/16" | 3/8" |
| 2" | 5" | 3/8" | 3/4" |
| 3" | 7 1/2" | 9/16" | 1 1/8" |
| 4" | 10" | 3/4" | 1 1/2" |
| 5" | 12 1/2" | 15/16" | 1 7/8" |
| 6" | 15" | 1 1/8" | 2 1/4" |
The two shrink columns answer different questions. "Add to center mark" is what the bender chart's 3/16" per inch is for: it lands the peak over the obstruction. "Total shrink" is how much shorter the whole run ends up, since the saddle is two 22.5° offsets back to back. Use it when something beyond the saddle has to line up.
How to bend it
- Measure the obstruction's height (for a pipe, its outside diameter plus any clearance you want), say 4".
- Measure from the end of the conduit to the obstruction's center line and add the center-mark shrink: 4 × 3/16 = 3/4". Mark it. This is the center mark.
- Mark the outer bends 4 × 2.5 = 10" on each side of the center mark.
- Bend the center 45° at the center mark. Most hand benders have a separate saddle mark (often a notch or teardrop) for the center of a saddle; use it instead of the arrow if yours does.
- Bend each outer mark 22.5° the opposite way, keeping all three bends in the same plane.
- Check it against the obstruction before you strap it.
Common mistakes
- Adding the total shrink to the center mark. That puts the peak past the obstruction. Use 3/16" per inch for the center mark.
- Using the arrow instead of the saddle mark for the center bend on benders that have one.
- Bending the outer bends in different planes, which twists the saddle.
- Too little clearance. Measure to the top of the obstruction, not its center.
Multipliers and shrink here are the rounded values used on bender charts. Benders differ; check yours and make a test bend on scrap for anything that has to fit exactly.
Questions
What is the multiplier for a 3-point saddle?
2.5 on most bender charts, for a 45° center bend and 22.5° outer bends. Each outer mark goes 2.5 × the obstruction height from the center mark. The exact trigonometric value is about 2.6.
What is the shrink on a 3-point saddle?
Bender charts give 3/16 inch per inch of height: add that to the measurement to the center mark. The run as a whole shortens by twice that, because the saddle is two 22.5° offsets back to back.
When should I use a 4-point saddle instead?
When the obstruction is wide, like a large duct or beam. A 3-point saddle peaks at one point, so it suits pipes and narrow obstructions.