Tape Width for Off-Center Carton Seams
Check the tape lying on each side of the seam, not only the total tape width. A strip placed off center leaves less tape on one flap and more on the other. A gap between the flaps also uses part of the width without providing carton surface beneath that part of the strip.
This geometry helps explain a placement problem. It does not establish how much contact is required for an acceptable seal. Obtain that requirement for the chosen tape, carton and application process, and evaluate the actual closure separately.
Measure three dimensions in the same units
Use tape width W, flap gap G and the absolute offset D between the tape centerline and the gap centerline. For a straight strip spanning a straight, uniform gap, the smaller contact width is (W − G) ÷ 2 − D. The larger side is (W − G) ÷ 2 + D.
T9077000 kraft fiberglass reinforced water-activated tape is listed at 70 mm wide and 450 feet long, with ten rolls per case. Its 70 mm width can be used in the geometry below. The roll length and case count do not enter this cross-seam calculation.
| Flap gap | Tape centerline offset | Smaller side | Larger side |
|---|---|---|---|
| 6 mm | 0 mm | 32 mm | 32 mm |
| 6 mm | 8 mm | 24 mm | 40 mm |
| 10 mm | 8 mm | 22 mm | 38 mm |
In the second row, (70 − 6) ÷ 2 = 32 mm before the offset. Moving the centerline 8 mm leaves 24 mm on one side and 40 mm on the other. The same strip has unequal contact widths even though its total width is unchanged.
Compare with your approved minimum
If the applicable process specifies a minimum contact width M on each flap, the geometric condition is W ≥ G + 2D + 2M. Use the minimum from the approved process, not a number invented from the tape width.
For a hypothetical arithmetic example only, set M to 25 mm, G to 6 mm and D to 8 mm. The resulting width is at least 6 + 16 + 50 = 72 mm. The listed 70 mm strip would miss that example's geometric condition by 2 mm. Twenty-five millimetres is not a Packrift or manufacturer recommendation.
Find whether width or placement is the issue
Measure the actual flap gap and strip position at several points. A crooked strip can have a different offset along its length. If the smaller-side result becomes zero or negative, the simplified model no longer describes tape contacting both flaps; inspect the arrangement rather than treating a negative number as usable contact.
Review flap alignment and tape placement before choosing a wider roll. Any different tape also needs its own product and dispenser checks. These measurements address available surface width; they do not prove adhesion, activation quality, bond strength or shipping performance.
Keep the measured gap, placement variation and required contact criterion with the approved carton-sealing method so a repeat order preserves both the tape specification and the application requirement.
See the water activated kraft tape buying guide for related product options.