many thanks indeed for all of you who took the time to respond to me
on this issue.
unfortunately there was none of the bolt remaining (after my failed
previous attempts!) to weld a nut onto and the car was sitting outside
the garage making things even more complicated. to cut a long (very
long) story short, i used a dremel with a chainsaw sharpening bit at
30,000rpm for about an hour which cut through the broken drill bit and
the steel bolt. amazingly, it did not damage the aluminum and i was
able to clean the hole with a drill and re tap it to the original 6mm
size. even more amazingly the hole was still aligned and the water
manifold bolted right up.
i also tried a diamond bit and a silicon carbide bit with less success.
the drill bit was a cheapo titanium nitride plated 1/16" bit from
harbour freight. i must admit, for the price, those bits hold up
amazingly well without needing sharpening.
- owain.
On Sat, Nov 15, 2008 at 6:52 PM, Owain Lloyd <owain.lloyd@gmail.com> wrote:
> 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?
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