Welding Tips and Tricks

Hello, I have a cast iron repair I need some advice on. I have been a woodworker for a number of years, and a buddy of mine gave me his old jointer, which has a cracked table. A new one is about $450, so I need to fix this one. It's made of cast iron, and not steel, unfortunately, and to add to the problem, it is a precision part; I do not want to preheat it. Also, I'm trying to decide what process to use, arc or TIG welding. I am just starting to get my certification in mig, so I'm relatively new to welding. I can stick weld pretty well also, but if that is the process I choose, then there will be spatter on the precision ground surfaces, and there will be a lot of restarts from stitching the weld together about a half inch at a time to lower heat imput. Then again, other option is to chip the flux off of the arc rods and use them for tig welding. TIG would be cleaner, and give me better restarts, but I'm not as good at TIG.
The top is surface ground, and the side is just machined, but either way they need to be flat and smooth when I'm done. Even though the side isn't cracked from this picture, it is broken on the back side. Should I break the piece completely off, or try and grind the bevel and weld it while the chunk is still hanging on by a thread, or leave it where it is? And then what process should I use?
I couldn't figure out how to add more than one picture, so I hope this is enough.

Sil-Braze

I have had very good luck with cleaning the flux coating from Ni-Rod and TIG welding in short stitches.

I got some time to do tests welding the cast today. I used an old pot from the kitchen for a test, instead of breaking the important part. Tried some oddball alloy rods that were laying around and they didn't work at all, to much heat and to big a diameter. Tried some 308 stainless arc rods and they were better, pretty colors what with the stainless and all, but they were still real hot. The lat thing I tried were the most likely to succeed, the Ni-rods. The only ones there were about fifteen years old, and they didn't work for $h!t, but they ran cooler (set em at 60 amps for a 3/32, and I'd like to go hotter) and cleaner than the others, and didn't try and crack at all. I gonna get some new ones, Hobart, I think, and just arc weld it with them. To much trouble to frig around setting up the tig welder, since it never gets used.

I had some success once welding a cast iron water valve cap for an elementary school with a tig, it didn't crack when I was done, never done it before or since, think it was beginners lock, but I didn't preheat it to the point it was really hot just too hot to touch

Man, I wish you hadn't posted that skillet. I had an old lady hit me with a skillet one time; many years ago. I still feel that one.


Anyway, since the part looks like it is just cracked, have you considered brazing it? I have heard that grinding cast iron can 'smear' the structure of the metal. I have used grinders before brazing, to clean out a joint, and I didn't have any joint failure.

Brazing is more structurally solid than you might think. Wire brush the joint, maybe run a thin cut off wheel into the crack just to open it up a bit - or not, based on my earlier comment.
Gary

Hi I do a lot of cast iron repairs turbo chargers etc. and where possible I always use the TIG with silicon Bronze filler.
For the job you are describing the important thing to note is that the weld must be completely flat when finished.
To arc weld this a Nickel rod would be the norm but the problem with this is, it leaves a very hard weld and is difficult to machine afterwards I know this because am also a machinist.
Much easier to machine is silicone bronze and gives a lovely finish.
Just grind out your part slightly you don't need to worry too much about penetration on cast Iron the silicon bronze flows nicely and gives a strong weld about 70% of the strength of a weld but with 30% more elongation,
so this makes it unlikely to crack.
Do preheat the part just heat it up to 150 degrees celsius ( 300f) , you can use the oven in your kitchen if you want. When you are finished welding just put a hand held torch on it for a few mins and spread the heat around and then let it cool slowly. I do this by putting in a bucket of sand or in my case my sand blasting cabinet. The result should be a nice weld easily machined or even filed and sanded. Hope this helps Bert