Thickness on a circular protector is the board build, and it behaves differently from thickness on a straight profile. A ring has no long leg to distribute load, so the board has to resist indentation across a narrow band, and a thick but weakly bonded board will delaminate at the inner cut before a thinner well bonded one fails.
What the board is asked to do
Resist the point where the coil rim meets the ring, spread stack weight across the band, and survive being pushed over the product without the inner edge tearing.
Those three are not the same requirement. A ring that fails on fit usually fails because the board is too stiff for the clearance, not because it is too thin.
Specification at a glance
The table pairs the duty with the board decision, in the terms a drawing uses.
| Duty | Board | Note |
|---|
| Light roll, push fit | Thin | Flexes onto the roll |
| Coil, face stacked | Medium | Spreads stack weight |
| Heavy coil | Thick | Bond carries the load |
| Tight clearance | Thinner | Seats without creasing |
| Strap held | Thicker allowed | Fit not the constraint |
Bonding and the inner cut
The inner cut exposes the plies. If the bond is poor, that exposed edge lifts and the ring starts to come apart in handling. That is why a ring is judged at the inner edge before it is judged on weight.
On a heavy coil the load path runs through the band to the inner edge, so the bond carries the load, not the paper alone.
Thickness and fit are linked
A thick board has less give, so it needs slightly more clearance to seat without creasing. Where the fit is tight by design, a thinner board is often the more reliable choice.
Where the ring is held by the strap rather than by fit, thickness can go up because seating is not the constraint.
A practical check before ordering: cut a strip of the proposed board to the ring width and bend it round the product. If the inner face creases, the build is too stiff for the clearance; if it folds easily but the plies separate at the cut, the bond is the problem rather than the thickness.
Questions buyers ask before ordering
What thickness range do you make?
It follows the board build available for the diameter; confirmed per drawing.
Is thicker always stronger?
No. A thick board with a poor bond delaminates at the inner cut.
Does thickness affect the fit?
Yes. Thicker board has less give, so it needs slightly more clearance.
Where does a ring usually fail?
At the inner cut, where the plies are exposed.
Can I get a board sample before ordering?
Yes, and it is worth checking the inner cut on it.
Send the product diameter, ring width and board thickness to mona@hengnicepacking.com and we will quote the ring that fits.
