Inside width is the clear gap between the two legs, and on a bendable channel it does two jobs at once: it decides whether the protector grips the panel, and it decides whether the notched corner closes cleanly. A channel that is right on a straight edge can still be wrong at the fold if the inside width was measured too tight.
Measuring inside width on a real panel
Measure the panel at the edge, in at least three places, with a caliper rather than a tape. Board thickness varies across a sheet and a channel cut to the thinnest reading will not go on at the thick end.
Where the variation is more than a millimetre, specify the mid value. A channel that is a little loose at the thin end still grips at the thick end; one that is tight is unusable on half the stack.
Specification at a glance
The table pairs panel thickness with the inside width we cut, allowing the fit a bendable piece needs at the notch.
| Panel | Inside width | Leg | Wall |
|---|
| 4 mm sheet | 5 mm | 35 mm | 2.5 mm |
| 12 mm board | 13 mm | 40 mm | 3 mm |
| 18 mm board | 19 mm | 50 mm | 3-4 mm |
| 25 mm board | 26 mm | 50-60 mm | 4 mm |
| 50 mm section | 51 mm | 70 mm | 5 mm |
Why the notch needs a little more width
At the fold, the two halves close against each other and the inner corner of the panel is the tightest point. If the inside width is exactly the panel thickness, the fold pinches that corner and the profile rides up.
A half millimetre of clearance at the fold is normal on a bendable channel, even where a straight channel on the same panel would be a close fit.
Width, wall and the leg all interact
As the inside width grows, the legs have to grow with it or the profile becomes a shallow tray that will not stay on. Past about 150 mm the geometry stops behaving like a channel and two L profiles back to back are the practical answer.
Wall thickness does not change the inside width, but a heavier wall reduces the internal clearance slightly because the fold is thicker. That is worth checking when a heavy wall is used on a tight panel.
Questions buyers ask before ordering
Do I measure inside or outside?
Inside, the clear gap between the legs. Outside is inside width plus two walls.
How much clearance at the fold?
About half a millimetre on a bendable piece, even where a straight channel fits closely.
What if the panel thickness varies?
Specify the mid value and allow the channel to be a little loose at the thin end.
Does wall thickness change the inside width?
Not the nominal figure, but a heavy wall uses some of the clearance at the fold.
What is the maximum inside width?
150 mm. Wider than that, two L profiles back to back work better than a stretched channel.
Tell us the piece size, quantity per shipment and how it is handled at mona@hengnicepacking.com and we will advise on the board build.
