basic screw question

20 Feb 2013
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United Kingdom

I will be installing some internal bifold doors which has a bottom rail and runners in the top. The head needs to be screwed to above support which is a catnic lintel with a steel RSJ sat on the catnic (there is a reason for this). Having looked in the screwfix catalogue I can see the self tapping Timco type screws but there are loads of different variations and I have no idea when it comes to metal screws. The instruction manual for the doors say use 5mm Tech screws for securing to an RSJ but could someone recommend a type? Pan head/countersunk/hex head? I take I need to pilot drill?
Any help would be much appreciated
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You definitely need to pilot drill, that is for the screw head, that can depend if you need clearance where a countersunk head could be needed.
Personally I'd go for a head that could be reliably tightened, such as allen or torx ......much less chance of mashing up the screw head!
John :)
"Tech" or "Tek" screws are nominally self drilling and self tapping - though to be honest I'd be sceptical of them being able to drill or tap the web of an RSJ which tends to be a bit harder than "mild" steel. They do work well on thin sheet - I've used them on up to about 3mm mild steel.

Hex heads are best used with the correct driver bit. I've seen them done by putting a socket in the drill chuck, but it's hard to get it tight enough not to slip. But the magnet in the proper bits certainly helps with screw placement.

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