Expertise

FAQs

What are the key dimensions you use to define a cardboard tube?

The key dimensions we use are as follows:

Length: Measured with a tape measure to the nearest mm for tubes of length 300mm and above, for tubes less than 300mm a Vernier is used to give a length to the nearest 0.1mm

Inside Diameter (ID): The inside diameter is governed by the size of steel spindle that that the tube is wound around. It is very difficult to check an unknown ID accurately with a vernier so for this reason we use plug gauges that slide inside the tube or core.

Wall Thickness: This is the thickness of the wall perpendicular to the circumference of the tube. It's relatively easy to measure with a vernier although care has to be taken to ensure consistent readings.

Outside Diameter (OD): This is used instead of Wall Thickness for tubes that must fit inside a component. We are able to manufacture to tighter tolerances on the OD than the wall and the OD is easily measured with a set of verniers.

How is the Inside Diameter of a tube measured?

It's difficult to measure the inside diameter of a tube accurately using vernier calipers. Verniers can be used as a guide but if the Inside diameter is a critical dimension then we always ask our customers to, if possible, send us a sample of their tube and then we use our full range of plug gauges to accurately match the customers requirement to the exact ‘spindle’ size required.

What is the thickest wall of tube you can manufacture?

The thickest wall we can produce is 18mm.

What is the thinnest wall cardboard tube you can manufacture?

We manufacture spiral tubes down to 0.45mm thick wall and convolute tubes down to 0.3mm wall.

What is your lead time for delivery?

Lead times vary between customers according to their requirements; their geographical location and type of product being manufactured. Some of our customers operate highly lean and flexible factories and need lead times of 24 hours or less, some of our customers order tubes a month in advance. As part of our sales process, we seek to understand what is required and develop the most cost effective and practical solution in partnership with the customer.

Do you use different grades or qualities of paper to manufacture your tubes?

For the most part we seek to standardise all our manufacturing on high quality High Performance Board. This gives all our customers an assurance of quality and performance consistency whilst minimising change over times and waste in our factory. However, we do stock a range of specialist boards for specific requirements. For example if you need extra strength but are constrained by the Outside Diameter we can use a higher grade of paper. If you need a tube with a particularly tough inside ply to prevent ware on a driving shaft we have options for this too.

What tooling do you use to manufacture cardboard tubes?

Cardboard tubes are manufactured by wrapping board (or paper) around a steel mandrel (or spindle). In our industry some people call mandrels, spindles and some people call spindles, mandrels! At Stell we use the word “spindle” to describe each tool we use. Each spindle is defined by its outside diameter and this defines the inside diameter of the cardboard tube – which we often to refer to as the ID. Convolute tubes are manufactured on a different design of spindle to spiral tubes. Either way we have the UK’s biggest spiral tooling library and the UK’s biggest convolute tube tooling library. We can always match exactly what our customers require.

How should I store my cardboard tubes?

Cardboard absorbs atmospheric moisture and so sudden changes in atmospheric moisture levels will cause the moisture level in the cardboard tubes to change. This can be problematic for longer tubes where one side of the tube changes moisture levels much more rapidly than the other. So, just like a plank of wood can warp, cardboard tubes can bend if they are not constrained and exposed to changing heat/moisture levels. For this reason we recommend cardboard tubes are stored in well ventilated, heated storage areas and not exposed to direct heat sources.

Sometimes tubes are defined by their Inside Diameter and Wall thickness and sometimes they are defined by their inside diameter and outside diameter. What’s the difference?

In terms of the manufactured sized of the tube there is obviously no different between a 76.4 ID tube with a 3mm wall and a 76.4mm tube with an 82.4mm OD. However, our convention is that for tubes where we know that the strength is critical we will define them with a wall thickness and for tubes where we know that the OD is critical we will define them with an outside diameter.

Do you manufacture waterproof cardboard tubes?

Cardboard, by its very nature, absorbs water and we use non toxic water based solvents. We therefore can’t make a water proof cardboard tube. However we do have a wax dipping process that provides a water resistance to the tube which is useful for pyrotechnic applications or where the tubes life needs to be extended.

Can you manufacture cardboard tubes to a specific crush strength?

Yes, we have our own in-house crush-testing facility and so can design tubes to with stand specific crush forces.

What’s the difference between crush strength of a tube and the beam strength?

The crush strength is a measure of how well a tube resists a force applied perpendicular to its circumference; this is often the critical strength when materials are wound onto the tube at high tension. The beam strength is a measure of how well a tube resists force applied perpendicular to its length when it is only supported at either end. This is often a critical measure of its strength when a tube is held between two chucks for a re-wind process or when it is being transported – for a wide web of material, you don’t want the tube to bend too much that it causes the material to crease.

What's the difference between a Spiral Cardboard Tube and a Convolute Cardboard Tube?

A spiral cardboard tube is created by applying glue to ribbons of paper and wrapping them around a steel spindle (see photo on home page). This leaves a visible spiral witness mark on the outside of the tube where two ribbons are running next to each other. These 'ribbons' are referred to as 'plies'. the length of the tube can easily be adjusted and the Wall Thickness / Outside Diameter is determined by the thickness and number of the plies used. In general, spiral tubes can be manufactured to tighter tolerances and higher quality of finish than convolute tubes.

A convolute cardboard tube is made from a single sheet of paper and is identified by the straight 'seam' running down the length of the tube. Due to being made from a single sheet, convolute tubes are more restricted geometrically than spiral tubes. However this single sheet fabrication gives them two distinct advantages: firstly they are able to withstand higher internal pressures (important for pyrotechnic uses) and secondly they have a higher beam strength (compared with the equivalent spiral tube) which means they can be a cheaper option for many textile applications.

What's the difference between a Cardboard Tube and a Cardboard Core?

Some people say Cardboard Tubes some people say Carboard Cores - the word core and the word tube is largely interchangeable but generally we would use the word core for a tube that has been cut to a 'shorter' length and the word tube for a 'longer' length. So that begs the obvious question of when does a length stop being 'shorter' and become 'longer'. To an extent this depends a bit on the Inside Diameter, something that is say 8mm in ID will look quite 'tube-like' at say a length of 100mm but something that is say 76.4mm in ID will definitely be more 'core-like' at 100mm

Confused?!

Well, don't worry, we specialise in manufacturing round things made from cardboard - whether they're called Cardboard Cores or Cardboard Tubes makes no difference to us!

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