What will drill out self tapper ?

[CompoSimmonite]

I need to remove, without damage, an alloy top off a steel frame. The top is attached with small counstersunk screws that have rusted solid to the steel frame and chewed up slots. Only option now is to drill out the screw head. Sound simple however brand new drill bits don't touch the screw as it's such hard material.
Any suggestions on what will drill them out ?

Thanks.

Paul H

 

[tigler]

Cobalt or tungsten carbide drill bits.

 

[brightspark]

loose the heads with a die grinder . quick and more controll

 

[breezer]

Cut slots into them with a dremel / grinder and then use an impact screwdriver

 

[breezer]

Sorry just re read COUNTERSUNK.

impact driver might still work on its own.

 

[ChrisJohnsSculpture]

A tile drill might do the trick, certainly cheaper than a carbide twist drill. If you were really sneaky you could re-grind it so it cuts in reverse so the torque is acting to loosen the screws.

 

[tab]

Are they chewed up as in rounded or is it possible to get a larger screwdriver to grip it a bit? The reason i ask if you have a screwdriver with a t bar (gets more pressure on it) heat the area up around the screw part is sat and not the head, bear all you weight on to it and try and tighten a little more, this might free it from the rust so you can then unscrew it. If that doesnt work try spraying the area in plus gas, leave over night and repeat the above.
I've had to do this many times at work when we have to save the screw as well but if you dont then my vote would be a cobalt bit as well

 

[CRB]

X2 tab,

If possible tighten first, usually works for me.