Why is an Ordnance Packing Box thicker at the corners than the walls?

Answer: The corner takes the first contact in a drop. At 9 mm it spreads a one metre drop without cracking, while 6.5 mm walls keep the box under 12 kg.

Can the insert be glued straight to the base?

Answer: Better not. A bonded insert has no float, so a 2 mm wall bow shears the seam. Spot adhesive plus clips leaves room.

What gasket compression should be specified?

Answer: 22 per cent. Under 15 the cord never beds; over 30 the closing force passes 200 N.

How many latches does the box need?

Answer: Two below 600 mm of rim, three above 800 mm. Too few and the cord loads unevenly.

Why cut the seal hole in the latch seat?

Answer: The seal must break before the box opens. A hole in the lap looks neater, but a gap can be pried with the wire unbroken.

Ordnance Packing Box: Five Structure Points and Their Process

Quick answer: An Ordnance Packing Box is settled by five process points: rotomoulded walls with graded thickness, an insert on moulded lugs, a groove with set cord compression, over-centre latches, and a seal hole in the latch seat.

Where the Ordnance Packing Box Gets Its Shell
Insert Fit and How It Is Held
Gasket, Valve and Moisture Control
Latches, Hinge Pin and Strap Channels
Marking Pads and Seal Holes
FAQ

1. Where the Ordnance Packing Box Gets Its Shell

The shell of an Ordnance Packing Box is rotationally moulded, so thickness is graded, not welded: 6.5 mm walls, 9 mm corners. Powder at 35 mesh swings at 280 °C for twelve minutes, then water cools it for eight, holding thickness within 0.8 mm.

Load gathers in the four corners and two bottom edges, never at mid-base, so the tool is built up 2.5 mm there, with recesses 1.5 mm deep for the insert lugs. The rim flange goes to 10 mm, since every latch load passes through it.

Zone	Wall	Made by	Does
Corner	9 mm	tool build-up	resists drop cracking
Rim flange	10 mm	extra water line	carries latch load
Base	7.5 mm	thickened floor	resists stacking

Past 9 mm a corner buys 5 cm of drop height for three more minutes of cooling.

2. Insert Fit and How It Is Held

An insert is a matched pair of cavities, not a foam sheet: the lower one is routed, the upper carries a press rib that squeezes the item 3 mm on closing. Moulded EVA at 38 kg/m³ returns 0.18 MPa at 25 per cent compression; PE foam at 30 kg/m³ takes a permanent set.

Ordnance Packing Box: pale grey corner close-up, lid and body rims aligned, a clamped draw latch, a square lug, a second lever at right

It must not be rigidly fixed. A drop bows the wall 2 mm, and a screwed-down insert tears at the seam, so four M5 screws per square metre plus six nylon clips leave 1 mm of float under a rim-set edge.

3. Gasket, Valve and Moisture Control

Sealing is a groove in the rim and a hollow EPDM cord of 9.5 mm, closing from a 5.5 mm deep groove to 7.4 mm, which is 22 per cent compression. Under 15 per cent water seeps through in half an hour; over 30 per cent the closing force passes 200 N.

Three layers do the moisture work: cord for liquid water, 250 g of molecular sieve per 0.1 m³ for vapour, holding 35 per cent internal humidity at 25 °C, and a purge valve cracking at 0.12 bar against temperature swings. The groove is moulded, never milled, since a Ra3.2 burr nicks the cord and leaks after 480 hours of salt spray.

4. Latches, Hinge Pin and Strap Channels

Over-centre latches lock themselves: 6 mm lever travel, 0.5 mm of spring-back past dead centre, 900 N each. Two put 1800 N on a 1.2 m rim, about 150 N per 100 mm; the count follows length.

Ordnance Packing Box: pale grey case open, black gasket ring in the lid, two wire stays, a coiled cable in the insert

Strap channels are separate, 3 mm deep and 30 mm wide, set between the latches, not across them. At 800 N the wall moves 0.6 mm in a channel and 1.2 mm over a latch seat. A 5 mm stainless hinge pin in an HDPE bush stays within 0.4 mm after 5,000 cycles.

5. Marking Pads and Seal Holes

Marking needs a flat pad: 130 by 90 mm, sunk 0.3 mm, laser cut 0.15 mm deep and still legible after 0.05 mm wears away.

The seal hole is missed most often. A 4 mm hole is cut through the latch seat and the lid, coaxial within 0.3 mm, taking a 1.8 mm wire and a 6 mm crimp. In the seat, the box cannot open without breaking the wire; in the lid-to-body lap, a gap is pried and the wire left whole.

Marking	Position	Process
Name and lot	lid pad	laser, 0.15 mm deep
Seal hole	latch seat and lid	4 mm, coaxial 0.3 mm

Conclusion

Graded walls absorb the drop, a matched insert stops movement, a moulded groove and sized desiccant hold the interior dry, over-centre latches survive vibration, and a seal hole in the seat makes tampering visible. Each pulls against another: thicker walls cool slower, higher compression closes harder. Settle those numbers on the drawing and an Ordnance Packing Box passes its first sample.

This article discusses only the container (case body) side of specifications and design intent, and does not cover any handling, loading or use of the contents.