Like I said...Best left to the Experts !!! :)
JC...

In a message dated 9/18/2004 10:03:56 AM Pacific Daylight Time,
donalds1@VERIZON.NET writes:
JB and fellow knuckle busters
there are 2 approaches to this one would be to just drill the head off the
bolt and remove the link and then try to turn the remainder of the bolt with
the help of the blue wrench (torch) and a good vise grips or core the entire
bolt and hope to remove the remains with a chisel. Easy outs might work on
new parts but in the real work of rust that trick never works
To drill out a broken bolt I grind the end flat and start with a 1/8 th inch
drill bit after marking the center of the bolt with a punch. Snap on tools
sells a great little double ended 1/8 th inch bit that has saved me many
hours of grief and go up in drill size as needed . The hard part of coring
out a bolt is to get the remains out of the hole without taking out the good
threads. To prevent damage to the threads I have found that the center punch
to mark the starting point of the drilling is the first thing to get right
and staying on center is next. I use a slow drill speed or the off and on
the trigger method to keep the bit speed down so as not to overheat the
drill bit end. The next important tool is a good quality punch I use a Snap
On 7/32 part # PPC107 LA straight shank 3.5 inch shank length punch. This
comes with a flat contact surface that I have ground to a 70 or so degree
angle without overheating and weaking the punch.  Once the bolt is cored and
the thin wall and threads are all that remain I use the punch to collapse
the wall and threads in on themselves this can be much harder to do if the
hole is blind. This can take out a little bit of thread so you want to use
caution and focus on the collapsed part of the bolt. If you decide then the
cored bolt is out that not enough thread remains ( That's NEVER happened to
me ) then I like Heli Coils brand thread repair rather than other types of
inserts except for drain plug repairs but that's another story

PS I own more Heli coil kits than the tool salesman

Going faster miles an hour with my new radio on
I remain
Boston Bob