Core size and roll diameter: making rolls fit your dispenser
Measure a honeycomb paper dispenser in five steps, put core and roll diameter on your order, and predict the diameter of a longer roll with one formula.
Picture a buyer who orders a full container of honeycomb paper. The width is right, the grade is right, the price is right. Then the first roll goes onto the dispenser and does not fit. The roll is too fat for the frame, or the core is too small for the spindle.
It happens because width and GSM are on every order, and core and diameter are on very few. I think it is one of the most avoidable problems in packaging.
So here is what to do. Measure four things on your dispenser: the spindle diameter, the gap between the side plates, the largest roll diameter the frame allows, and the path the paper takes out. Then put the core inner diameter, the maximum roll diameter, the flat width and the flat length on your order. If you are moving to a longer roll, you can predict its diameter from a sample with one formula, given below.
How do you measure your dispenser?
You need a steel ruler or a vernier calliper, and five minutes per dispenser. Take the old roll off first.
- Spindle diameter. Measure the shaft or the core holders at their thickest point. The core's inner diameter must be a little bigger than this.
- Gap between the side plates. This sets the widest roll that fits. The roll needs a little clearance on each side, or one edge drags.
- Distance from the centre of the spindle to the nearest obstruction. That might be the base plate, a guide rod, the brake arm or the bench. Double it. That is the largest roll diameter the frame can take, before any margin.
- Brake contact. If the brake presses on the roll's outer surface, check it still reaches a nearly empty roll. If it acts on the spindle, note that the pull will feel tighter as the roll gets smaller.
- Paper path. Note whether the paper leaves from the top or the bottom of the roll, and over which rod. Take a photo. This tells you which way round the roll must sit.
Write the five numbers on a label and stick it on the dispenser. When someone orders paper in two years' time, the answer is right there.
What to write on the order
| Dispenser measurement | What it becomes on the order | Why |
|---|---|---|
| Spindle diameter | Core inner diameter, with a small clearance | Too tight: the roll will not go on. Too loose: it wobbles and walks |
| Gap between side plates | Flat width of the roll | A roll that rubs one plate opens unevenly |
| Largest diameter the frame allows | Maximum roll outer diameter, with a margin | A fat roll rubs the frame or will not go on |
| Brake type | No line on the order, but note it | Tells you how the roll will behave near its end |
| Paper path | Which way the paper should unwind, if your dispenser cares | A roll loaded the wrong way feeds badly |
I would also ask the supplier for the full roll weight, because someone lifts it onto the spindle. Our roll weight chart gives the paper weight for every width and GSM.
How do you predict the diameter of a longer roll?
A roll is just paper wound around a core. Its diameter depends on the core, the length of paper, and how much thickness each turn adds. That thickness is the paper's own thickness plus a little air, and it changes with winding tightness. So do not guess it. Work it out from a roll you already have.
The formula for the roll diameter is:
D = √(d² + 4 × L × t ÷ π)
Here D is the roll's outer diameter, d is the core's outer diameter, L is the flat length of paper, and t is the effective thickness of one turn. Keep everything in millimetres.
To find t from a sample roll, turn it round:
t = π × (D² − d²) ÷ (4 × L)
A worked example
Picture a fulfilment centre that tested a 100 m sample roll and now wants 250 m rolls. These measurements are made up to show the arithmetic. Use your own.
- The sample roll measures 160 mm across. Its core measures 82 mm across the outside.
- Effective thickness per turn: t = 3.1416 × (160² − 82²) ÷ (4 × 100,000) = 3.1416 × 18,876 ÷ 400,000 = 0.148 mm.
- Predicted diameter for 250 m: D = √(82² + 4 × 250,000 × 0.148 ÷ 3.1416) = √(6,724 + 47,110) = about 232 mm.
- The dispenser's frame allows 240 mm before margin. That is too close for comfort. A roll wound a little looser, or one that has taken up moisture, can be bigger than the calculation.
So the centre has two choices: check with the supplier that the 250 m roll is wound tightly enough to stay under about 230 mm, or move the guide rod. Either way, it knows before the container leaves, not after.
Why do real rolls differ from the calculation?
Three reasons, and you should allow for all of them.
- Winding tightness. A loosely wound roll is fatter and softer, and it can slump on the spindle.
- Moisture. Paper swells a little as it takes up water from the air. Our guide to storage and humidity explains why damp rolls give trouble.
- Shape after transit. A roll that was stored or shipped carelessly can go oval, and an oval roll bumps on every turn. Check a few rolls from each pallet for roundness with a tape around the middle and around each end.
This is why I would put a maximum diameter on the order, not an exact one.
What about the core itself?
The core is the cheapest part of the roll and the one that causes the most quiet trouble.
I would always ask for the inner diameter, the wall thickness, the length and the core type. A core that is shorter than the paper lets the edges sag. There are three types, and your dispenser decides which one you need.
| Core type | What it is | When to choose it |
|---|---|---|
| Flush core | The core is exactly as wide as the paper | Most table-top dispensers and hand use. The standard choice |
| Extended core | The core sticks out beyond the paper at one or both ends | Holders that grip the core ends, and long transit, because the roll edges are not crushed when rolls touch |
| Notched core | Notches are cut into the core ends | Dispensers and machines with a hub or brake that keys into the core, so the roll turns with the brake and cannot slip |
Look at how your dispenser holds the roll. If it has a smooth spindle, a flush core is usually right. If arms or cones grip the core ends, an extended core keeps them off the paper. If the hub has lugs or teeth, it needs a notched core, or the roll will spin freely and the brake will do nothing. Check the ends are round and uncrushed, because a crushed core end makes the roll wobble even on the right spindle.
If you already own dispensers with different spindles, one core size may not suit them all. Collars and adapters can bridge a small gap. Our guide to honeycomb paper dispensers covers how to fit them and how to set the brake.
Where we fit
We make cores in 25, 50 and 75 mm inner diameter, as flush, extended or notched cores, and we customise the diameter, the colour and the print to order. So the core can be built for your dispenser, not the other way round. We also sell a table-top manual dispenser made for our 380 to 390 mm x 250 m rolls, with a tension control knob. If you already own dispensers, we confirm the roll diameter and core on the quote to suit them. Our products page lists both.
I should admit one thing. We cannot see your dispenser from Jaipur. If the numbers you send us are wrong, the roll will still not fit, however carefully we make it. So measure twice.
Send us your five dispenser measurements, a photo of the hub that holds the core, and a photo of the paper path through our contact page. We will check them against our roll before you order.
Questions buyers ask
What if my dispenser spindle is bigger than the roll's core?
The roll will not go on, and forcing it will crush the core. Ask your supplier for a core that fits your spindle, and give the spindle diameter in millimetres on the order. Do not cut or ream the core yourself.
Can I use a coreless roll on a dispenser?
Not on a dispenser that holds the roll on a spindle. The spindle needs a core to sit in. Coreless rolls suit holders that cradle the roll from underneath, so check how your dispenser holds the roll before you ask for one.
Can two narrow rolls run side by side on one wide dispenser?
Sometimes, but I would test it first. Two rolls rarely have exactly the same drag, so one tends to open better than the other. It works best when each roll has its own brake.
Why does a new roll wobble when the old one did not?
Usually because the new core has a larger inner diameter than the spindle. Fit collars or an adapter, and write the correct core size on your next order. A crushed core end does the same, so check the core is round.
