Some cast iron repair

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A friend has an antique woodworking lathe that the toolpost broke in half and was poorly repaired by someone so it broke again.He wanted to see if I could repair it to keep the original look and build a new one if he wanted to use the lathe.The old repairWas just going clean out the old weld and put a bevel on it but kept hitting bad material/weld so had to grind it back a lot more than I wanted.I will do some more cleaning of the paint and rust in the morning and pre-heat with the propane rosebud before welding. The top side I'm going go fill with 3/32" non machinable nickel rod and the bottom will get a piece of round bar filler and welded.  After it's all finished I'm going to plasma a piece of 1/8" or 3/16" to put on the bottom with some silicon bronze tig rod just to beef it up a little. (That's the plan at least)What would be a good pre heat temp?Has anyone tigged cast iron with silicon bronze before?TOO MANY TOOLS & NO MORE SPACE
Reply:Hi, just as a matter interest, as You don't have the equipment I have for welding cast iron.....I weld cast iron using a Multiplaz 3500 plasma welder, of which much has been talked about, and have welded a number of cast iron objects using mild steel welding rods for the filler.This forms an alloy which is not cast iron or steel, but high carbon steel around the weld zone, and provided the part is pre-heated and allowed to cool slowly it doesn't break.The last job I did 2 weeks ago was for a clamp for a circular saw bench belonging to a friend of mine.....something he wanted to sell on.You could probably get near to something I do with the plasma using a Tig if you do the pre-heat and cooling properly.Ian.
Reply:Originally Posted by Chris T.A friend has an antique woodworking lathe that the toolpost broke in half and was poorly repaired by someone so it broke again.He wanted to see if I could repair it to keep the original look and build a new one if he wanted to use the lathe.The old repairWas just going clean out the old weld and put a bevel on it but kept hitting bad material/weld so had to grind it back a lot more than I wanted.I will do some more cleaning of the paint and rust in the morning and pre-heat with the propane rosebud before welding. The top side I'm going go fill with 3/32" non machinable nickel rod and the bottom will get a piece of round bar filler and welded.  After it's all finished I'm going to plasma a piece of 1/8" or 3/16" to put on the bottom with some silicon bronze tig rod just to beef it up a little. (That's the plan at least)What would be a good pre heat temp?Has anyone tigged cast iron with silicon bronze before?
Reply:Should also add silicon bronze is very expensive. 16.70 per lb at my LWS opposed to 2.10 per lb for steel wire.
Reply:I'd say that repair would be better off with brazing than welding.
Reply:You may wish to try aluminum bronze, I used it to repair a cast storm drain grate. posted the repair in "what I welded today" used AC and it lays down nicely.RegardsGreg
Reply:Originally Posted by swampwelder13I did a cast iron pot not too long ago with si bronze after 308l would not work. It worked for the pot but I dont think it could be used on that piece you have. only suggestion I have is flip your machine to ac and lean more towards the negative side. That was best results for me over that dirty cast.
Reply:Cleaned the remaining paint and weld out with my little 2" angle grinder. Preheated with the propane rosebud to 400deg and tacked the long part to the bench. Used a piece of angle iron to keep the sides straight and tacked the short part to the bench.I had to fill the gap with a piece of 1/8" x 1/2" flat bar and it melted in real nice. After the two parts were one again, I cut it off the bench and started welding.I put in two beads just to build up some thickness and then turned up the power to fill it in alternating top/bottom & left/right sides to spread the heat out. After each pass, I used a needle gun to remove the slag and peen the weld. Every couple of passes I'd light the rosebud and wave it over a couple times to keep the part between 400-500deg.It looks like bird poo on the top because I just put some weld in to build up so it could be ground down to match the profile of the part. After it was finished, I went over with the rosebud a couple times and folded it up in a fire blanket to cool.TOO MANY TOOLS & NO MORE SPACE
Reply:Wasn't going to say anything but I agree with G-son brazing would be my way to go.
Reply:The finished product.TOO MANY TOOLS & NO MORE SPACE
Reply:Nice job Chris.TA Arcmaster 300CM3XMT 304S22P12 suitcase feederX-Treme 12VSOptima pulserTA161SMaxstar 150STLHypertherm PM45OP setupStihl 020AVP, 039, 066 Magnum
Reply:Originally Posted by Drf255Nice job Chris.
Reply:Machined the rest of the pieces this morning and welded it up after lunch.After a lot of grinding to replicate the profile of the original we have a finished product. Went over it with the needle gun to simulate cast iron.I made it so he could use either a 5/8" or 1" tool rest which is common on all woodworking lathes of this size.TOO MANY TOOLS & NO MORE SPACE
Reply:The two different bushings did not post for some reason.TOO MANY TOOLS & NO MORE SPACE
Reply:That looks great!!
Reply:Originally Posted by Murphy's lawThat looks great!!