I was mounting an alarm sensor onto my shiny new aluminium door frames and it turned out that I chose the wrong size of pilot drill and the worst material to use as a self tapping screw.

I’m left with a 2-2.5mm brass screw sheared off almost flush in the frame – but just convex enough that I can’t drill into it.

Any thoughts? Anyone fancy centre-boring a 3mm drill bit for me ?

Centre pop it first to guide the drill bit

If it really is brass in aluminium, you may be able to get it out by putting a Jewelers type screwdriver on it and tapping it with a hammer.  jewellers screwdrivers usually have pretty sharp ends. Brass should be soft enough that the screwdriver will cut its own slot.  Brass is soft enough that the threads won’t gall – it is sometimes used as bushings.  You may need to buy a new screwdriver though.  Or just sharpen an old one

Or as spennyy says centre punch it – a sharp/sharpened nail is a good substitute for a centre punch.  Don’t use a nailset – those have the wrong shaped end

Can you get enough of a hole in the end to use an easy out (LH thread) that screws into the drilled hole, then it bites and unscrews the remaining screw? I suspect its probably too small to do that though.

Brass self tapper?

Are you sure its brass and a self tapper?

Sharp centre punch. Drill out carefully to a size suitable to tap to a thread size that you possess screws of.

Grind it off flat with a dremel and move the sensor slightly and drill new holes? Assuming it’s the first one you should be able to cover it.