How to make a pipe saddle template
To make a pipe saddle template, cut a paper strip as long as the branch pipe’s outside circumference, divide it into equal lines, and mark each line’s cutback: how far back from the long point the cut sits. Join the marks with a smooth curve, cut on it, wrap the template on the branch and scribe the cut.
Drawn by Stretchout from the worked example below. Parallel line development.
What you need
- Paper, poster board or light sheet for the template
- A tape and a straightedge
- Dividers or a scale for the spacing
- A flexible batten or French curve
- Soapstone or a scribe
Worked example
We’ll lay out a 4" pipe (4.500" OD) teed square into an 8" main (8.625" OD), on center, 16 lines. The numbers:
- Main OD
- 8.625"
- Branch OD
- 4.5"
- Stretch-out (around the branch)
- 14 1/8"
- Line spacing
- 7/8" × 16
- Drop, long point to short point
- 5/8"
Step by step
Step 1
Draw a baseline 14 1/8" long: the stretch-out. Square a line up at each end.
Step 2
Divide it into spaces 7/8" apart (16 around the whole pipe) and square a line up from each mark. Number them from the left.
Step 3
Mark each line up from the baseline for the cut. The top edge stays square:
Line Mark up 1 0" 2 1/8" 3 5/16" 4 9/16" 5 5/8" 6 9/16" 7 5/16" 8 1/8" 9 0" 10 1/8" 11 5/16" 12 9/16" 13 5/8" 14 9/16" 15 5/16" 16 1/8" Step 4
Join the marks with a smooth curve (a flexible batten helps) and cut on it.
Watch it laid out
Every step of the worked example. Play, or step through with Next and Back (or the arrow keys).
1.Draw a baseline 14 1/8" long: the stretch-out. Square a line up at each end.
The formula for a 90° tee on center
With the main’s outside radius R and the branch’s outside radius r, the cutback on a line at angle ψ around the branch from the long point is √(R² − r²·cos²ψ) − √(R² − r²).
The long points are the two sides of the branch across the main, where it reaches furthest down around the pipe; the short points sit on top of the main, and the drop between them is R − √(R² − r²). Those are the numbers in the example above.
At an angle or off center there’s no short formula: the cut is where every line of the branch meets the main, worked out line by line. That’s what the calculator below does, for any angle from 10° to 170° and any offset.
Questions
How many lines should I use?
16 lines is plenty for most branches up to about 8". Go to 24 or 32 on bigger pipe, so the batten doesn’t have to guess between marks.
Where is the long point on a saddle?
On a square tee it’s the two sides of the branch across the main: the branch wraps furthest down there. The short points sit on top of the main, in line with it. The cutbacks are measured back from the long point.
Does this work for a lateral or an off-center branch?
The method does, the tee formula doesn’t. At an angle the long point moves to the heel of the lateral and the two sides of the cut stop matching. Put your angle and offset into the calculator on this page and it gives the cutback for every line.
Should the template be the OD or the ID?
Lay out on the branch OD to wrap and scribe it in the field. For a set-on branch welded to the outside of the main, the branch ID is what sits on the main; the calculator has a setting for it.
Does the template thickness matter?
For paper, no. For sheet metal or thick poster board, the stretch-out should be taken at the template’s own mid-thickness, a little longer than the pipe’s circumference, or the ends won’t meet when it wraps.
What about the hole in the main?
The hole is its own template, wrapped on the main. The calculator’s shop view draws both the branch wrap and the main hole.
Your sizes
Below is Field Fit, opened on the worked example. Put in your own sizes and it redoes every number and every step for your fitting. It’s also at /stretchout/field-fit.