removing an API thread from small drill stem pipe

It seems I may have finally broken at least 1 contractor from sucking eggs. for years now every time this contractor had broken bolts or fittings their mechanic would try to remove them, and almost always wound up having to bring the offended part to me to repair. Usually with broken easy outs or after welding on them to try and remove the dutchman or broken bolt.
Yesterday their boss showed up at my place and dropped off 5 drill stems for their horizontal drill rig. He said he was sick and tired of having to pay 4 times to get broken bolts out every time his mechanic tried, he would have to take the part to a local welder where they were working only to have to send it the 100 miles to me in the end for me to fix everyone's screw ups.
Let's see what you have this time Dale.
OK if you have an hour or 2 to kill I can have them ready for you or you can stay and watch I'll only charge double for the audience.
It would be worth the extra just to learn your secrets but I'm afraid I would try and explain to my mechanic how you go about it and that might only work for these items then he would screw something up so bad that you would have to make a whole new piece and I'd wind up paying for a new part. I'll see you Monday
A little over an hour later this is what I had.
These are the treads from broken drill bits they are tightened up initially with a hydraulic tong then the boring process makes them tighter and tighter until the torque is too much for the thread
Attachment 43045
I started out clamping the drill stems in my pipe vises
Attachment 43046
Then burned out the center of the dutchmen's
the core is still read
Attachment 43047
Once cooled the #7 extractor had no problem removing them
Attachment 43048
First job I did for this contractor that went as it should, no cuss no fuss.