[Tigers] need some advice - non tiger

[Owain Lloyd]

ok guys - i'm consulting the tiger list because i know how much
expertise is here.  sorry if that irritates anyone!

i was changing the timing chains and tensioners on my jaguar XJR v8
when i accidentally sheared a 6mm bolt that holds a water elbow to the
heads.  the bolt is steel - the head aluminum.  that was my first
mistake.   i tried penetrating oil, heat, shock, vice grips, cutting a
slot in it and nothing worked.  so i carefully got a centre punch in
it started drilling it out with a right angle drill attachment.  then
came my second big mistake...  the small drill bit snapped of about
halfway though.   now i've tried a larger bit and a masonry bit but
nothing budges this very thin bit.

my plan now it to get hold of some solid carbide bits and, taking it
slow, try and drill it out with that.  failing that i suppose i can
tap a couple of small threads on each side of it.

any advice before i make it even worse?