# Tigging cast iron...



## cathead (Mar 29, 2020)

Today I decided to clean up an old capstan that came from the scrap yard several years ago.  On inspection,
I found out why it was discarded.  One of the teeth on the big gear was missing!  I saw that as an opportunity
to fire up the Everlast TIG welder and at least try to attempt a repair.  I thought of gas welding on a tooth with
some brass but with a new TIG sitting there, I didn't have to cogitate too long to decide what to use. 
The biggest difficulty was seeing what I was doing but I could see well enough to see that the base metal was
melting.  I fed in some pieces of broken piston ring for filler rod in the process.  I did some rough profile work with
my 4.5 inch angle grinder using a thin cut off tool.  The repair looked better than some of the other teeth on the
gear so I think it will work OK.  
	

		
			
		

		
	




Yes, it looks a little rough but probably fine for what I am going to use it for.  
	

		
			
		

		
	



It turns freely past the new tooth!  It would be a handy tool to pound in a sand point well.  It can be powered with a small gas engine and also has provision for
using it on a PTO.  Now I have to wait patiently until the ground thaws around here...


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## RJSakowski (Mar 29, 2020)

I hope that you properly heat treated the repaired area.  Cast iron turns into white cast when cooled quickly and is brittle.  On a piece that small, I would simply heat the whole piece.  Soaking at a temperature 800ºF for an hour or so and then slowly cooling to room temperature swould convert the white cast as well as relieving any thermal stresses from the welding process.


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## cathead (Mar 29, 2020)

I guess I improperly heated the gear...


Time will tell the story.  If the tooth breaks off, I can have another go at it.


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## cathead (Mar 29, 2020)

In the meantime, I did some reading on the subject of TIG welding cast iron.  There is a TIG welding wire
called EZ Weld that one can use for cast iron welding without preheating.  Another possibility that I would
consider trying would be to TIG weld using a nickel rod used for arc welding of cast iron.  Nickel can take on
a lot of carbon before getting hard.  Also noted is the fact that nickel needs to be welded in a well ventilated
area as the fumes are hazardous.  I think I will call the project complete for now.


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## epanzella (Mar 29, 2020)

I always like to see someone pushing the shade tree mechanic envelope! It's where I live!


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## ericc (Mar 30, 2020)

When I have gas welded with cast iron rods, everything gets all pasty, but it seems to wet in.  I do notice that if I let the weld cool without putting a blanket on it, it will get a little hard, but not too hard so that a file will not cut it.  From what I have seen, white cast iron will skate a file.  The deposit is probably harder than it should be, but my repairs have held.  I've yet to try this with a TIG welder, since I fear the heat is much more localized than a gentle torch flame.  It has been a huge pain to cut the cast iron rods out of broken drain covers with a hacksaw, but recently I acquired a bunch of junk piston rings and am eager to try them out.


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## Cooter Brown (Mar 30, 2020)

I never try to TIG braze or weld Cast iron, its to easy to over heat it with TIG...... I have much better luck using low fuming bronze with black flux.....


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## cathead (Mar 30, 2020)

Cast iron piston rings come in really handy and work very well for welding cast iron.   Not all piston rings are cast iron however.  
It is easy to tell because if you pull them apart and they break, they are cast iron and if they just bend, they are made of stainless
steel.  I usually weld several broken pieces to make my own custom made welding rod, been doing this for years.  Extra points given 
for outside the box thinking. 

Like this:


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