I guess its good to show some failures too. Here the 3/4" drill pipe stripped out. In a few different attempts to get it out, the lip was bent over as shown. As a last resort, a cheap bore camera was sent down to see what was going on. A chisel was welded to more pipe and sent down with the camera for alignment. After being hammered in, it was un-threaded from whatever joint wanted to give up first, and pulled out. Good drill pipe was then sent down and re-threaded and the whole thing removed. The failure was about 15-20 feet down with another 20-25 feet of pipe plus the drill bit below it. Went up to 1" drill pipe at that point. If I had to buy it all again, I would probably have went with 1-1/4" or 1-1/2" pipe. Its all gets so heavy though.
Here is a small video of the bore and the broken pipe.
This was a previous project for testing a percussion drill. The tower was not built as I like to test for failure in stages. What I didnt know at the time was that a pounder required 600lbs per inch of bit. Two inches means 1200lbs and this contraption wasn't designed for that. With only 35lbs on the bit, this run for 6 hours and went absolutely nowhere through solid limestone. I later core drilled this out to see if it done anything and it didnt even chip the rock in the slightest.