The device must be sealed carefully to achieve the IP-67 rating.
It is difficult to provide an exact torque figure with which to tighten screws. This is because upon first sealing the device, the screws cut threads into the nylon glass housing. So on the first assembly, the screws may be quite stiff. If the housing is opened and then resealed, the torque required for resealing will be lower than that of the first assembly.
The key goal we are trying to achieve in sealing is firm, even pressure on the silicone seal - as this is what keeps the device water-tight and dust-proof.
To achieve this:
- Ensure that the clear silicon seal is in good condition, is lying flat, and is not fouled by any plastic debris or other material.
- Close the housing, and gently squeeze it shut. Foam on the lid will compress against the batteries, holding them firmly in place.
- Tighten the 4 screws to uniform tightness - such that there is an even gap at all points along the interface between the base and lid.
- The screw heads are Posi-Pan head. As such a Posidriv bit should be used. A Phillips screwdriver can strip the threads.
- The screws are a thermoplastic screw: 2.5mm x 8mm (BN82428). If you are after a stainless steel variant, the product code to source is BN82429.
- It is a good idea to use a screwdriver with a torque limiting clutch, start with the screwdriver on the lowest setting, and gradually increase the torque until there is a small gap between the base and lid (no need to overtighten as you risk cracking the housing)
- The final torque when finished will be around 0.7Nm most of the time. (Value is a guide only)