Self tapping screws

[ibexman]

Whats best fat or thin thread or may be self drilling????

[timmymac]

I would imagine a fine thread and probably not self drilling so you can use a smaller drill to keep it really tight,could be wrong but at a guess its what i would do or use rivets.

[FridgeFreezer]

My sheet tin shed uses self-drilling fairly coarse thread screws (hundreds of the b*ggers), wlthough it may help to describe what you're trying to do - horses for courses and all that.

[Ally V8]

If you sharpen a thin punch then use it to create a hole,the inward curved edge can create extra area for the threads of the screw to dig into - if that makes sense.

[Night Train]

A deep, coarse thread could turn the thickness of the sheet into one turn of thread. That may, in some cases, be better then a couple of turns of finer thread.

I prefer inserts and rivnuts on thin sheet.

[heath robinson]

If you want to achieve the same effect as the screws fixing my factory galvy light-guards to my bodywork, then it's all about the quick, coarse screw

In all seriousness, those things have one fights with stonework, foliage, and farm machinery. I undid them (For what is i suspect one of the very few times since '84, and certainly the only time in the last ten years) a while ago, and they did back up as tightly as ever.

[LandyManLuke]

I'd definitely say a thicker, coarser thread, so that the thin sheet becomes one thread of a 'nut', as mentioned above.