In case anyone was wondering how this project turned out, we did win.
The broken ream did not respond well to the carbide faced masonry bit. It did chew chips off the ream when put on light hammer. Cobalt had no effect and was not worth the purchase. The chipping away action made the ream fracture at a fairly steep angle, so I made up a drill guide plug with a steep angle on it to approach matching the broken ream. Inserted the drill and guide plug, hammered and turned for a bit. Pulled it out to check progress and determine if centered. Grabbed custom air tip with
16" tip, stuck it down the bore blowing out chips, dust, coolant, etc and there was a loud thunk on the concrete floor as the tip of the ream fell out!!! Only thing I can figure is the angled faced guide forced the ream to turn and loosen.Now all we had to do was remove the old heater shell. Sounds simple. I had two plans, neither of which worked. Plan one - drill a hole in the bottom end cap of the heater tube to be able to pump grease and force out the shell. I had even made up a piston or sorts to maximize a hammer blow on a rod to pressure the grease (reserved execution for later). Plan 2 - I had experimented in the shop with another damaged heater and found that a 5/8-11 tap would start and cut threads in the stainless shell without just tearing it to bits or swelling it larger than the bore (prime idea). Tapped about 3/4" of threads in the end of the shell and was able to remove extension and tap. Screwed in a
3' section of all thread and had rigged a piece of pipe to function as a slide hammer. We made several attempts at this and even used an 18" pipe wrench to wind the all- thread into the shell. We succeeded in stripping the threads off the all thread, but the stainless shell was still very happy to live in the guts of the chiller.Tried the grease idea - boy, was that a mess! But now I figured maybe it was loosened and it certainly was lubed! Tried the all thread again, no progress. Getting mad now.....
Went out to the truck rummaging and came up with a 24" long SDS drive 5/8 masonry bit. It wasn't very fresh or sharp, but what the hey. Figured if nothing else it would make the shell spin in the hole. No it wouldn't. But by turning it on hammer and drill we actually dug into the shell. It did not drill as such, it just turned to grit. It was the first progress we had made. Drilled a bit deeper, enough to see another shell from another heater in the top of the bore. Apparently it had been drilled out before and they had not gotten all the old one out. Continued on for over an hour hammering the stainless shell to dust, never did get the shell to spin or get the old old shell to let go.
Ended up with a clean enough, deep enough bore to allow the new heater to slide in, wired it up, and walked away. I should be retired before this heater dies again.
Thanks for all the suggestions and advice. Gunner, my next step was to try to weld onto that piece of ream; but turned out not necessary to try.