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My appologies also, I had not noticed the misspelling (and being a poor speller myself, repeated it) but was only commenting on the (somewhat confusing) use of the word shear (sheer) to indicate a very smooth fracture. snip
Repair of cast is an inexact science because of the difficulty of determining exactly what kind of cast we are working with and there are many ranges of quality. Real cast iron was often used for making machine tools due to its rigidity and ease of machining and it was usually the cheapest, especially for limited production quantities. Modern high quality heavy machinery is far more likely to be cast steel, but smaller (especially offshore China, India, Malaysia) and especially cheaper stuff is a real guessing game. One good indicator is that it is usually the poor quality stuff that needs repair (YMMV). IMHO, The OA cutability test is your best friend. Some people like the spark test but I have not learned to do this reliably.
I have learned not to be too hasty to jump to brazing to repair cast metal (iron or steel) because once you add brass to the area it is hard to go back to steel. I have often repaired cast steel using xx18 and have had very good results from steel electrodes (trade name ferroweld?)designed for (nonmachinable) repair of cast iron. (Small welds, controlled heat input and piening are big factors in success.) I am not a big fan of any of the Ni rod family as they are very expensive, hard to weld and I have had mostly poor results with them. I will use them if I need to drill or tap the weld metal but in these cases I generally prefer brass.
Anytime I see broken cast I like to ask myself if it is possible to replace the broken cast with fabricated steel even if it means welding a small piece of steel onto a larger cast housing. (A good example of this is welding a (domed, there is a trick to this) piece of thin plate into a large engine block holed by a thrown rod.) Nonmachinable steel stick electrodes work quite well for joining steel to cast and are stronger than brass.
I generally prefer brazing (IIRC brass has a higher tensile strength than cast iron) for repair of smaller cast pieces and have had good luck with this when I was able to take the time to do careful and complete prep work and to control the pre and post heat and welding temperatures carefully. Use an old BBQ or make a small custom oven with firebrick and old fibreglass insulation if you can. Some use a barrel of vermiculite and bury the repair for slow cooldown but IMHO this creates its own health concerns.
I think you are doing the right thing by doing lots of research and thinking before rushing into this repair. It looks like a quality tool that deserves careful work.
Good luck, YMMV