Long Screws into Aluminium

[Andrew]

I am fitting a pocket door and the frame is an aluminium box section. The instructions assume that the stud wall will be a metal construction and advises screwing through the metal upright into the aluminium frame using a self-taping screw.

But my framing is timber so I will need something like a four inch self-taping screw to fix in the same way. I could get away with something a bit shorter if I counter-bored the timber first.

The frame is already installed so any holes in the aluminium will have to be drilled through the timber.

Any suggestions?

[alan_m]

Often a self drilling and self tapping screw which are designed to pull the two sections of metal tightly together, with the two sections of metal temporarily clamped before drilling/screwing.

Or drill a hole the size of the screw head on one side of the box section ali to gain access to the inside of the box in order to screw into the opposite side of the box section with a shorter screw into the wood. Find rubber/plastic bungs to fill the hole(s)

[The Natural Philosopher]

Or drill and tap for a suitable bolt like M5

[John Rumm]

In which case you could probably get away with a normal twinthread wood screw (the end profile is not that different from a self tapper). Predrill the ali with a drill the same size as the core of the screw, and you will probably need an impact driver the drive the screw,

Another less aesthetic option would be to drill and countersink the frame and screw from that direction into the timber.