Last week I managed to drop my back door key somewhere over the course
of a several-mile dogwalk. Oh well; at least it can't be tracked to my
house, so no security issue; and I have a spare key at home, so no
worries there.

Except, of course, I cannot find the spare. Have searched high and low
to no avail, and it's doing my nut in not being able to open the door,
so it's time to do something about it.

Having read up a bit online I reckon I can get an angle-grinder blade to
the bolt down the door jamb, and cut through it
(http://i.imgur.com/kpA6U9u.jpg) However I'm a bit concerned about the
presence of what looks like reinforcement down the middle of the bolt.
Or, could it be ball-bearings designed to resist attempts at cutting?
As it happens, I have an identical lock on another door - photo of the
bolt is he http://i.imgur.com/NWnHW9k.jpg

I don't want to attack the lock and completely bugger it up - what do we
think my chances of success might be, with this approach?

Thanks
David.