I am planning to install lighting on the machine hall, which is made of sandwich panels at the top. I was thinking of installing classic 'yard lights'. That is, a fixture on a 30-50 cm long 'arm' where the 'arm' has a mounting plate with usually 4 holes intended for a type of French bolt (8-10mm) to screw into a barn wall of wood.
I have been to some hardware stores and tried to ask if it's just a matter of using regular sheet metal screws but get very vague answers. The sheet metal screws are also very small compared to the holes in the mounting plate.
The sandwich is 120mm thick and consists of metal-foam-metal and I am myself very doubtful about attaching something so heavy to only the outer metal sheet. Do I need through bolts? Or is there some sort of 'special screw'?
I have been to some hardware stores and tried to ask if it's just a matter of using regular sheet metal screws but get very vague answers. The sheet metal screws are also very small compared to the holes in the mounting plate.
The sandwich is 120mm thick and consists of metal-foam-metal and I am myself very doubtful about attaching something so heavy to only the outer metal sheet. Do I need through bolts? Or is there some sort of 'special screw'?
I would recommend using a through bolt with a nut and a square washer on the inside. The sheet metal is so thin that it is difficult to get something heavy to stay in place, especially on an arm as in your case.
https://www.ahlsell.se/10/infastning/skivinfastning-a2bc2c14/metallexpander/301792/
I personally use these to hang tool boards, hose reels, etc. in my workshop where there are sandwich panels.
Perfect
I personally use these to hang tool boards, hose reels, etc. in my workshop where there are sandwich panels.
Perfect
I felt stuck but now I have very good tips on how I can feel confident that the stuff won't fall down in the next storm...