How would you fix this old cast iron?

[Doc Nickel]

I'm just starting to fix up an old Rockford 'camelback' style drill, and I need to patch up one spot. Apparently sometime in it's long history, someone smacked the upper table-raising screw support, and it broke a section out of the casting.

http://www.docsmachine.com/machineshop/rockford10.jpg

Or the old bolts rusted in place and somebody decided to whack 'em out with a chisel, or whatever. Regardless of how it happened, there's a bloody great hole in the side of my column, and in the interests of aesthetics, strength and a place to bolt the screw mount, I want to fix it.

http://www.docsmachine.com/machineshop/rockford11.jpg

It's roughly 3/4" high and about 3" long, and the casting is better than 3/8" thick.

The question is, weld or braze? A stick weld with a high-nickel rod would be easier, but the braze, I think, might be safer- I do not want to crack this thing any worse than it is. There's a lotta force on the column as the drill pushes through a big piece with the power feed, so I want it to be as strong as possible.

Second question: I have some old cast sewer pipe of roughly the same diameter (though now that I think about it, I'm not sure it's the same thickness.) Would it be better to make the patch out of that, or from a section of mild steel pipe?

The casting is pretty good sized, and pretty awkwardly shaped. How hot should I preheat it, either for welding or brazing, and what would be a good heat-resistant insulator to put over it- the weld and the rest of the casting- after welding?

[edit] Third question: What do you think about the idea of making a diamond-shaped patch, larger than the hole, and brazing it to the inside, over the hole? It'd be a tricky issue trying to clean and smooth the inside of the casting, but apart from that, if the patch were pre "tinned" with braze and flux prior to placing it over the hole, it might work, and add a measure of additional strength to the repair.

Doc.

[Carm]

Hard to tell from a pic whether it actually is weldable, but chances are, yes.
Clean it up, shiny, light grind. If you can't get a bit of shine(looks dirty, or keeps "smearing") you're in for trouble.
Fill it with dry sand and use some f/g or more dry sand on the outside. If you preheat to 300-400F , good to go with stick or TIG. I would use the nickle and peen every pass, to stretch and not allow shrinkage stress. The intent is avoiding carbon pickup, that's why brazing is safer, but then you have low yield. Could also silicon bronze TIG, same low yield.
If you don't have the missing piece, I'd just puddle 'er full, probably switch to steel after you butter everything up. Take a break once in a while so it doesn't get too hot. I like Tempilstiks if I'm doing something tricky.

[centervolume]

Doc,

it's going to be a lot easier to get a clear picture of the work to do on this job once you have cleared your docket of previous unfulfilled orders. You know, like those aluminum replica guitar nobs.

[macona]

I would make a pattern and make a new part for the support.

The rest I would tig braze in filler with silicon bronze rod. It works great to fill up sections of cast. And it puts in a whole lot less heat than welding.