What screw fixings are used on a composite door, e.g. for a door knocker?
The door construction is, apparently, 4mm GRP + 37mm PU foam + 4mm GRP = 45mm overall (related image from the Hurst website below), so not much bite into any thing solid using ordinary timber screws. The foam itself seems to be quite crumbly ('friable').
My actual application is a wireless camera doorbell, which I want mounted front and centre, between the decorative panes. I mention a door knocker above as it also requires some mechanical integrity.
I was thinking either something that bites into the foam (a coarse screw thread, or some kind of rawlplug + screw), or long bolts (e.g. a 3 or 4mm screw with a sleeve, door handle type) all the way through.
The latter would require knowing if there's anything more solid between the panes, like any metal reinforcement. Door handle screws also don't have much head diameter, as they have an escutcheon both sides, so ideas welcome.
Any real experiences out there??
I will contact the suppliers, but I am guessing they'll just mention warranty, or some other obfuscation.
The door construction is, apparently, 4mm GRP + 37mm PU foam + 4mm GRP = 45mm overall (related image from the Hurst website below), so not much bite into any thing solid using ordinary timber screws. The foam itself seems to be quite crumbly ('friable').
My actual application is a wireless camera doorbell, which I want mounted front and centre, between the decorative panes. I mention a door knocker above as it also requires some mechanical integrity.
I was thinking either something that bites into the foam (a coarse screw thread, or some kind of rawlplug + screw), or long bolts (e.g. a 3 or 4mm screw with a sleeve, door handle type) all the way through.
The latter would require knowing if there's anything more solid between the panes, like any metal reinforcement. Door handle screws also don't have much head diameter, as they have an escutcheon both sides, so ideas welcome.
Any real experiences out there??
I will contact the suppliers, but I am guessing they'll just mention warranty, or some other obfuscation.
