Round Offset Cut Length After Fitting Takeoff

Offset geometry gives the theoretical centerline travel, not the straight pipe cut. Calculate the centerline travel, then subtract the actual takeoff of fitting 1 and fitting 2. Do not subtract a separate crimp allowance again if insertion is already included in the fitting takeoff.

Straight pipe cut = theoretical centerline travel − fitting takeoff 1 − fitting takeoff 2. Use verified takeoffs for the exact fittings and do not subtract insertion twice.

Round, Spiral & Oval Duct 2nd Year YELLOW

Stop if

Ask when the fitting takeoff is unknown, the fittings do not match, the offset is rolling, or the measurement reference is not clear.

Watch out

Do not cut the straight piece to the raw triangle length. Do not guess one universal elbow or crimp takeoff. Do not subtract insertion twice.

Check

Is the measurement a true centerline offset?
Is the angle 30°, 45°, 60°, or another verified angle?
Are both elbows/fittings the same size and series?
Are the takeoffs measured to the connection ends using the same reference?
Does the published takeoff already include the slip/crimp insertion?
Are the elbows rotated in the same plane or is this a rolling offset?

Steps

Measure the true offset and confirm the angle.
Calculate theoretical centerline travel: offset ÷ sin(angle).
Identify the exact elbow or fitting at each end.
Get each fitting takeoff from the actual fitting, approved shop data, or manufacturer dimensions.
Calculate straight pipe cut = centerline travel − fitting takeoff 1 − fitting takeoff 2.
Dry-fit and verify orientation, airflow direction, rotation, and insertion before final fastening.

Say this to your foreman

I have a [size] round offset of at °. I calculated centerline travel, but I need the takeoff for these exact fittings before cutting the straight piece. What takeoff should I use for each end?