Job examples
- Collar that fits over a fitting12" inside, 26 ga.Stretch-out 37 3/4".
- Sleeve with a seam14" outside, 24 ga, 1" for the seam.Cut 44 7/8".
- Mystery pipe sizeTape around the pipe reads 37.699".It's 12" pipe.
How it's calculated
Circumference = π × D. Stretch-out is taken on the centre of the metal: π × (inside D + T) or π × (outside D − T). Cut length = stretch-out + your seam allowance, which depends on the seam and the machine.