Fixing with screws: Ventilated substructure

Distances between screw fixing points according to sheet thickness

Example 1

An advertising sign made of KÖMACEL, measuring 1500 x 1000 x 10 mm (59 x 39.4 x 3/8"), is to be mounted to a ventilated substructure using screws. The screw shaft diameter should be a minimum of 5 mm (3/16").

Determine the change in length and the hole diameter to be drilled:
Minimum surface temperature: -15°C (5°F)
Maximum surface temperature: 45°C (113°F)
Temperature differential: 60°C (140°F)

Solution: round hole

Overall change in length = 7.2 mm  (9/32")
Hole anchoring point = screw shaft diameter (5 mm) + 2 mm = 7 mm  (3/16" + 5/64" = 9/32")

The change in length is reduced by half in each direction from the anchoring point. Therefore, the following hole diameter is needed:
Holes allowing for movement = 7.2 mm/2 + 5 mm = 8.6 mm  ( 9/32" / 2 + 3/16" = 11/32" )
Hole diameter = 9 mm (23/64")

Anchoring point

In addition, the hole center distance from the sheet edge should be 2.5 times larger than the drilled hole.

Example 2

Using a KÖMACEL sheet measuring 3000 x 1000 x 10 mm (118.2 x 39.4 x 3/8"), with a screw shaft diameter of 5 mm (3/16"), compute the anchoring points according to the direction of movement (direction of extrusion). (Movement crosswise to the direction of extrusion is less pronounced, and the required tolerance for a sheet measuring 1 m (39 3/8") wide can be assumed to be approximately 3 mm (1/8").

Solution: elongated slot

Overall change in length = 14.4 mm (9/16") Hole diameter of anchoring point = screw shaft diameter (5 mm) + 2 mm = 7 mm (3/16" + 5/64" = 9/32") Hole allowing for movement, elongated = 14.4 mm/2 + 5 mm = 12.2 mm (9/16" / 2 + 3/16" = 31/64")

Holes allowing for movement