I bought a used industrial machine (a huge pipe threader).
It is a super nice machine in all respects and was rebuilt in 2007.
However, the reason why it was sold for nothing is that the cast iron transmission case in it is cracked due to a past accident.
The picture, with the crack highlighted, is here:
You can visualize this as a rectangular casting with one corner broken off. The three highlighted areas are in fact one crack separating only two pieces.
The size of this is about 1x1x2ft.
What I need to do is put it back together. Put in funny terms, I could take these pieces, clean them and "glue" them together, the question is how.
Real glue, obviously, would not work.
Nickel welding would likely not work well either.
It would seem that the pieces could be taken out, really cleaned up, pushed together, heated red hot, and brazed with brass.
Does that make any sense?
What would be the best approach?
If you can get it out and apart, I would try drilling and tapping some holes and bolt it back together so you don't have to worry about thermal stresses, more cracks, heat treat, keeping it square and aligned, etc. In the picture the bottom crack would need bolts perpendicular to the shaft with the gear but each hole would only total about 2" or 2.5" deep. For the upper crack the holes will be parallel to the gear shaft and the non-threaded holes are going to be 3" or more, then the shorter threaded holes, so not trivial but maybe you can find someone who owns a big mill :-) :-). Maybe someone can recommend something better but I'd use bolts that are 1/3 to 1/2 of the plate thickness when you go into an edge, so 3/8 or maybe 1/2" bolts if your casting is 1" thick. Counterbore and use socket head cap screws if you don't have clearance for hex heads on the surface. Grade 5 bolts just to avoid the horrible variable quality of anything less, thread engagement of double the bolt diameter since the bolt material is stronger than the cast iron, and torque with a torque wrench in a couple of steps.