# Welding Repair,... Cast Iron?



## Robo_Pi (Mar 28, 2019)

I didn't see a forum section on welding.  But I know a lot of machinists also weld.  I'm wondering if anyone can give me some hints on how to repair an old vice.   I'm guessing this is cast iron?

Here are some photos of the vice and a nasty crack in the casting. 

Top view: (actually I guess this is really the bottom of the vice jaw).

The crack starts at the lower left corner of the rectangular cut out on the round shaft.   And continues all the way around to about the midpoint on the other side (see side view  photo)




Side view:




I have no experience welding cast iron.  But I do have experience welding steel to steel. 

I have 3 methods to weld.

1. Oxy-Acetylene torches and lots of flux-coated brazing rod. 
2. An old AC/DC stick welder
3. A brand new TIG welder. 

I would like to TIG weld it if possible.   But I'm not sure what I need to do that.  

Are their special rods I'll need to get for welding cast iron?

*Two more Question on pre-welding preparation:*

1. I'm thinking I'll need to grind a V-groove all the way down the crack.   But I thought I'd double check here whether that's actually needed?   I didn't want to hack into this thing with a grinder until I get some feedback.  

2. I've always heard that cast iron needs to be preheated before welding lest it might crack while welding it due to extreme temperature changes.   If that's true what does it take to heat it up?  Should I just heat it up with the oxy-acet torch for a while before welding it?  And if so, how hot does it need to be. 

Thanks for reading and for any suggestions or guidance you have to offer..


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## bhigdog (Mar 28, 2019)

Cast iron HATES to be welded. 
That said, yes pre heat by torch to about 500F.
Yes, VEE it out.
Most guys stick weld using a nickel alloy rod.
Some guys like to post weld cover to slow cooling.
Likely lots of different opinions will be expressed.
Pay your money and take your chance.
Expect to be disappointed but what the Hell......................Bob


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## Bob Korves (Mar 28, 2019)

Deep V groove, complete grinding until clean metal showing everywhere.  Lots of the proper flux for brazing, and appropriate brazing rod.  Slowly heat the entire piece, flux, then heat crack area until the brazing rod flows into the V groove and fills it all, add a bit extra to make sure it is filled completely and the braze bonding to all the crack surfaces.  Insulate the work well so it can cool down very slowly.  Fire proof blankets or deep ashes all around the part work well.  Let it sit until it cools completely.

TIG can be used, but as it often done it does not heat the entire piece enough to equalize the stresses in the entire part.  It is more difficult to do without proper training, the biggest problems being cold joints that fail and stress cracks from uneven heating.


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## bill stupak (Mar 28, 2019)

What they said, and you need to find the exact end of the crack and drill a hole to keep it from going any further. 1/8" should suffice


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## Robo_Pi (Mar 28, 2019)

Thanks for the awesome quick advice fellows.  

Based on the feedback thus far I think I'll go with trying to braze it just using the oxy-acet torch.   Come to think of it I'm pretty sure I have repaired cast iron things in the past using brazing.    I know they can be welded nowadays,  But as has been pointed out welding cast iron probably takes far more experience and proper tools than I have available,.   So brass it will be. 

By the way, this vice isn't an expensive item.  I picked it up at a yard sale.   I took it apart to restore it just for myself.   But when I took it apart I saw this nasty crack.  Apparently it was last used as-is with this crack in it.   I mean, it's actually usable as-is.   But clearly it could break at any moment.  I thought I should try to do something with this crack before reassembling it.  

It's not like anyone will need to depend on this to get them to Mars.  

I'd just like to do something with this crack before putting it back together and trying to use it.   It's a pretty nice sized vice that I could put to good use.  I'll try to avoid putting heavy metal pieces in it and beating on them with a sledge.  

So thanks for the feedback.  I just braze it up then.  I think I can handle that.   Nice big deep vee groove with a drilled hole at the end of the crack.

That's what I'll try to do. 

Dag blast it.  I just bought that TIG torch and the darn thing is useless.    Better off with the old-fashioned oxy-acetlyene and some brazing rod. 

Should I get special brazing rod?

I just bought a ton of this General Purpose brazing rod.

I hope I can use this stuff:

I got it at Amazon:

*Blue Demon Gas brazing Rod* 
I actually used this rod last fall to repair my outdoor wood boiler stove.  I was welding on very old rusty corroded steel and this stuff flowed onto it really well.  Of course, I ground it down the best I could, but even grinding it down didn't clean it perfectly.  Yet this brass rod seemed to find a way to flow and stick even over rusty pitted areas.   I was impressed. 

I hope it will work for this vice repair.  Like I say I bought a ton of it, (well, actually only 10 lbs.   ), but that's a ton of brass rod. 

I'll try brazing it with this stuff.  Like I say, I'm not going to Mars with this vice, so if it fails, so be it.   It won't be the end of the world.   At least I'll still be on my home planet.


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## cbellanca (Mar 28, 2019)

I have done both. I depends on how much stress the part sees in service. As thin as the part is stick welding would be at real chore with an AC welder. Getting the heat right presents an undercutting problem. Brazing is much easier.  I would follow the prep, preheat and cool down advice above for ether process.  I don't think a hole at the end of the crack will help in this case.


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## pontiac428 (Mar 28, 2019)

Preheat and TIG with silicon bronze.  Easy and you'll be glad you did.  Let it cool slow.


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## benmychree (Mar 28, 2019)

One added suggestion, after veeing the crack out, feather the edges of the vee at a slight angle so the braze can flow out a bit, maybe just 1/8" or so, then butter up the whole thing with silver solder flux so that torch heat will not blacken the surface to be brazed and make it difficult to get the braze to adhere; this I do always when brazing cast iron.  I usually "tin" the surfaces with braze, then go back and fill to finished level with additional braze metal.  Try to not overheat the iron, just barely red is plenty hot, just hot enough for the braze to flow without boiling it, causing porosity.


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## Robo_Pi (Mar 28, 2019)

pontiac428 said:


> Preheat and TIG with silicon bronze.  Easy and you'll be glad you did.  Let it cool slow.



I didn't even know that you could braze with TIG until I saw Tony do it on a "This Old Tony" video.    That kind of got me interested in trying to use the TIG torch for this repair.   After all I just bought the TIG welder last year and would like to use it.  

But then I'd need to buy the special silicon bronze rod right?

I guess if I just go with the old-fashioned oxy-acetylene I can use the brazing rod I already have.    I'm probably over-thinking this one too much.  It's just an old vice repair.   I only paid $25 for this vice, which would have been a great deal had it not been broken..  I didn't see the crack until I got it home and took it apart.  I'd really like to restore this vice to some level of use.   It doesn't need to be super strong.

I'll probably just go with the oxy-acetylene brazing rod I already have.  Save the TIG torch for other projects.  Lord knows I have enough other projects that I will be able to use the TIG torch on.    So it's really no big deal if I don't use the TIG for this one job.


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## AGCB97 (Mar 28, 2019)

James
Yes there is a welding forum and I have gotten replies there to my questions.

With that new TIG you're itching to use I would braze it with aluminum/bronze (1st choice) or silicon/bronze. Do what others have said with cleaning, Veeing, SLOWLY preheating, and cooling very slowly. You don't want to get it hot enough to melt the base metal. That will make it brittle.  sometimes use an electric frypan with cover for pre and post heating. Bring temp up slowly and after brazing use heat and turn down gradually.

Here is a good video on doing just what you're trying.




__





						welding tips and tricks brazing cast iron - Bing video
					






					www.bing.com
				




Good luck
Aaron


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## royesses (Mar 28, 2019)

I used silicon bronze on the pivot arm on my 4x6 bandsaw. I had leaned over the saw to get a drop off piece and put too much weight on it. That was 3 years ago and it is not going to break. I just tig bronzed it and also the bandsaw vice nut which was broken in 3 places. Both have held up very well. You might need to pre heat that large piece first. Clean and vee it.

Roy


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## pontiac428 (Mar 28, 2019)

Robo_Pi said:


> But then I'd need to buy the special silicon bronze rod right?




Don't worry, it's cheap as far as that stuff goes. It's useful for many repair processes, so you might even find it at your local hardware store.


Edit:
Preheat the part by building a brick "oven" around it to contain the heat.  This will also slow cooling after, so win!


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## westerner (Mar 28, 2019)

Good stuff! I have a very small bit of experience, and alot of time listening to my uncle, he of MUCH experience. Good advice given above! The experience I have is on thicker material, (1/4 to maybe 5/16). Part weighed 8-10 lbs total. I used an AC stick welder with high nickel rod. You will not see penetration like 6011. You will want to hold a longer arc, and sorta spray the molten rod. Lots of preheat (oxy/acet rosebud), stress relief, and a very slow cool. Stress relief consisted of a pneumatic needle scaler, applied IMMEDIATELY after stopping the weld, and don't be gentle. Slow cool was "bury the piece in woodstove ashes for a day", immediately after the welding was done. The parts/jobs/projects were- 2 different transmission/transfer case adapters, for 70's vintage domestic 4wd vehicles. Both jobs resulted in parts that did not crack, did not leak, and are still in service more than a decade later.


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## Robo_Pi (Mar 29, 2019)

This tube I'll be brazing on is 1/2" thick. 

Here's a better view from the back end.

You can see the crack at the bottom of the rectangular slot heading off to the right.   It goes exactly half way around.   So this jaw is being held on by a half-circle of 1/2" thick casting.   That's why it didn't break off entirely I guess.   It's a pretty heavy duty vice.   I think it's still worth trying to rebuild.  But yeah I'll be able to grind a really deep vee-groove in this.   There's a lot of material there to braze to.






pontiac428 said:


> Don't worry, it's cheap as far as that stuff goes. It's useful for many repair processes, so you might even find it at your local hardware store.



I'll look around and see what I can find.  I'll probably need to order some.  I live in a rural area where there aren't too many decent hardware stores around anymore.   There used to be, but they all closed up.  Sadly. 

I would like to try to TIG braze this just for the learning experience.   But we'll see how it goes.  If I get in the mood to braze before I get the proper TIG rods I might just braze it up with gas.



pontiac428 said:


> Preheat the part by building a brick "oven" around it to contain the heat. This will also slow cooling after, so win!



I actually have a blacksmith forge.   I wouldn't heat it up too much.  But I could certainly warm it up in there quick enough.  

I also have a couple old propane cooking grills that I use for heating things up.  I don't use propane on those anymore, I just burn scrap wood in them when I need to heat something up.   They have the nice cast cover that holds the heat in pretty well.   Like others have said, you don't need to get it too hot.  In fact, the idea is not to overheat it.   300 to 500 degrees F should be plenty.   

Not sure when I'll do this welding.   I'll grind the vee-groove first.   I do projects around here a little bit at a time.   That's just how I work.  I'm usually doing 10 things at once.   So I do a little bit on each thing.   So it may take this project a week to get completely welded.


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## cathead (Mar 29, 2019)

I would probably vee it out and braze it or possibly see how the casting welds first. Cast iron piston rings broken in half are generally
of good quality and work well for rod in my experience.  Rings that break in half are cast iron, if they just bend, they are likely chrome
rings.  Several ring halves can be welded together so you don't have to hold on to short pieces.   Sometimes, I just don't like going
to town just for a welding rod or two.  That's my cheapskate tip of the day. 

In any case I would do a preheat and slow cool down..


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## Cooter Brown (Mar 29, 2019)

You can preheat it with a torch but make sure the post heat it and wrap it up in a welding blanket to cool slowly.... I have trouble with Cast Iron TIG brazing, I would use Low fuming bronze with stay-silv black flux and an Oxy Torch, Its way easier to screw up when TIG brazing....

This is a repair I just did to my shaper vise with low fuming bronze...


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## rwm (Mar 29, 2019)

pontiac428 said:


> Preheat and TIG with silicon bronze.  Easy and you'll be glad you did.  Let it cool slow.


Whenever I have tried this, I have had some melting of the base metal creating a brittle joint. I played with the welder settings but I could never get it right so the base metal did not melt to some degree. The joint looked fine but failed too easily when tested. I have had much better success with OA gas braising. This creates a consistent strong bond.
If you do go that route, Welding tips and tricks (Jodi) has some videos on this.
Robert


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## fixit (Mar 29, 2019)

http://www.locknstitch.com/index.ht...QSN_wnHSUIKCksYqv3UlK5PDZ2i3WppIaAki1EALw_wcB 

I worked for many years repairing & servicing Large air compressors ( up to 2000 hp & as old as 1934) this is the way we repaired cracks the cast parts. It's amazing how well this method will hold broken parts together.


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## Robo_Pi (Mar 29, 2019)

I cut the vee groove today. 

I'm not going to weld it today though. 

The vee-groove is only about 1/4" wide at the top.  I didn't go below the crack.  This is 1/2" material.  The vee-groove I made is probably only about 1/4 deep.  I could do deeper.   What do you think?  I didn't want to grind clear through and leave a big gap on the bottom where the brass can fall through while molten.





As I got around to the bottom the crack actually disappeared in the bottom of the vee-groove.  So it must not have been cracked clearly through on that part of it.





My current plan for welding is to preheat the whole thing to about 400 degrees. I even have an oven thermometer that I can use to assure I'm at that temp. 

I've decided to go with the gas torch and the brazing rod I have.   My plan is to go over the entire crack first with just a tinning pass, and then go back and fill it with brass. 

I might try to get to this tomorrow if possible.


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## Robo_Pi (Mar 29, 2019)

I just noticed a second problem with this vice.   I may as well fix that too while I have the thing hot. 

Right behind a vice jaw screw the vice is broken:







I figure I can just gouge this out with the grinder and fill it full of brass.  Then redrill and tap the hole.   All it does is hold the vice jaw in place so it won't have any stress on it. 

May as well fix that too while it's hot.


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## pontiac428 (Mar 29, 2019)

I'd be more inclined to do it in a single pass.  The second pass you will lose heat control trying to make the electrode flow like the previously deposited pass, plus you will have used flux (and the impurities it caught the first time) everywhere.  Cast iron may be a PITA, but brazing is easy.  Work a complete weld from one side to the other in one pass if you can.


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## Cooter Brown (Mar 29, 2019)

If you can see the end of the crack, drill a 1/4" hole right at the very end to stop the crack from starting again...


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## Robo_Pi (Mar 29, 2019)

pontiac428 said:


> I'd be more inclined to do it in a single pass.  The second pass you will lose heat control trying to make the electrode flow like the previously deposited pass, plus you will have used flux (and the impurities it caught the first time) everywhere.  Cast iron may be a PITA, but brazing is easy.  Work a complete weld from one side to the other in one pass if you can.



There won't be any electrodes involved.   I've decided to braze it with oxy-acetylene torch.   I think a double pass will be fine.   Although it may not be needed it all depends on how well it flows.  Often times when I'm brazing with gas I find that it's useful to do a tinning pas first and then come back and do any structural filling on that tinned surface.



Cooter Brown said:


> If you can see the end of the crack, drill a 1/4" hole right at the very end to stop the crack from starting again...



It's not clear precisely where the crack ends.    Besides I really don't think that will be necessary in this particular case due to the geometry of the overall part and the type of stresses involved.    Once I have this brazed up I don't think that crack is going to start back up again.


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## Cooter Brown (Mar 29, 2019)

Over fill it you can always grind it off, and its better than heating it back up again...


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## Tim9 (Mar 29, 2019)

I’ve used nickel rods a couple of times on cast but tend to prefer the O/A brazing for cast iron. No matter what you use I’m guessing you’re going to have to clean it up in the lathe when finished since it appears that the round tube must fit into the other half of the vise?


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## rwm (Mar 30, 2019)

I like your plan. Do you have access to a sandblaster? That might help get the entire crack chemically clean. 
Robert


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## Robo_Pi (Mar 30, 2019)

Tim9 said:


> I’ve used nickel rods a couple of times on cast but tend to prefer the O/A brazing for cast iron. No matter what you use I’m guessing you’re going to have to clean it up in the lathe when finished since it appears that the round tube must fit into the other half of the vise?



I am thinking of cleaning this up in the lathe.  If I can hold it.  My lathe has a 17" swing so the swing is large enough.  This jaw is only 10" across the largest diagonal.  So it will fit in the lathe.  I have a 6" 4-jaw chuck I think will hold it.   I'm even thinking that I could make a temporary cap for the open end with a lip on it to slip in the open end and use a live center to hold that end.   Then I'd be able to turn the whole thing down perfectly. 

I'll probably do that.  The other alternative would  be to try to hand grind it with an angle grinder till I get it to just clear.  That would certainly work, but wouldn't be as nice as actually turning it to true dimension.




rwm said:


> I like your plan. Do you have access to a sandblaster? That might help get the entire crack chemically clean.
> Robert



Yes, I have a small sand blaster that I can use to sandblast the crack before I braze it.  Good idea.   I'll do that.     I don't think I'll be welding it today.


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## westerner (Mar 30, 2019)

As a community service announcement, I gotta say this-
Nickel rod, aka "cast iron rod", comes in several flavors. One flavor is "machinable", and another is "non-machinable".
Believe me when I say that they mean it when they say "non-machinable". Dont ask me how I know


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## Robo_Pi (Mar 30, 2019)

Thanks for the tip.  If I ever mess with nickel rods I'll remember to ask which kind they are.   I'd definately like to turn this down when finished.  But that's clearly not going to be a problem at all using the brass rods I have.


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## Robo_Pi (Apr 7, 2019)

Boy the welding and casting forum is slow.  This thread is still at the top of the stack. 

It's been 10 days since I posted this thread and I finally got around to brazing the vice.

I'm happy with the results, but they could have been better.   To begin with I couldn't find my large welding tip.  I could only find the small one.   So I tried using the small one on the screw repair behind the vice jaw.   First I heated the whole thing up over a wood fire.   I don't know how hot it was but it was so hot I couldn't even hang onto it very long with brand new welding gloves on.    I did manage to braze up the broken jaw screw hole.  But it was going way to slow with that small tip, and I didn't like the way it was flowing.   So when I moved on to welding up the crack I used my 4-burner cutting torch to braze with.  

That worked way better.   In fact it worked absolutely beautiful for the first half of the crack.  The braze rod was getting sucked into the crack like a vacuum cleaner.  Very good deep brazing.  And the top of the brass was nice and flat, almost perfectly flush with the top surface. and not even sunken in.   But then I had to stop and turn the piece in the vice to braze up the second half of the crack.   I didn't stop for long only long enough to readjust the workpiece in the vice.   But then I couldn't seem to get it hot enough to really suck in the brass after that.   I tried to be patient and waiting for it to get as hot as I could get it, but despite my  best attempts the whole rest of the brazing job was a real fight with trying to get the brass to flow nice.  It tended to ball up and not want to wet out.   I was having so much trouble I even stopped and hit the thing with a wire brush.   But that didn't help.  

I did manage to lay down some brass on the second half of the crack, and some places wetted-out better than others.    Overall I'm ok with the finished brazing.   The worst part of the crack took the brass really well.   So that was the more important part I think.    In any case, I'm going to let it be and move on to just cleaning it up and putting it back together. 

This is the good side of the brazing job.   Not sure what it looks like in the photo, but it looks really good in person. 




This is the bad side of the brazing job.   Can't see it very well with the sun shining on it.  But it definitely looks amateur with a few balls above the surface.  I just couldn't get those balls to wet in.   It's not all bad, there were places where it flowed better than others.   I'm thinking that it was because I was getting close to the massive vice head and that was sucking up all the heat?  I think I could have done better if I could  have found my bigger torch.   Even my four burner cutting torch isn't all that hot, but it did work.




So now I'm ready for the clean up stage and the reassembly of the vice. 

If I had done this for a customer I'd be ashamed to ask money for it.  

Like I say, the first half was beautiful.  Looked and felt professional.   But the second half petered out and made me look like an idiot.   I think it will hold though and that's good enough for me.   I just blame it on the missing large torch.


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## rwm (Apr 7, 2019)

Looks like a winner to me!
Robert


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## john.k (Apr 7, 2019)

Ive found brazing with a cast iron scaling powder cures a lot of ills with proper wetting.............but for a heavy item like the vise,preheating to near red heat is essential..........otherwise the filler will never "wet" the cast iron,as the brass melting temperature isnt reached in the iron,only on the surface..............as to nickle arc welding rods..........maybe Bill Gates can afford them.....I cant.


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## john.k (Apr 7, 2019)

Another point,even the messiest braze is easily fixed by pre heating to red heat,coating with flux,and remelting the brass filler,when it will flash over the iron in a perfect braze as soon as brass melting temp is reached.......in fact ,with preheat ,its often a challenge to stop brass from flashing everywhere,because its hard to remove  from unwanted areas.


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## Robo_Pi (Apr 7, 2019)

john.k said:


> .............but for a heavy item like the vise,preheating to near red heat is essential.........



That was most likely the problem.   At the beginning of the crack the crack was wide and you could see right through it easily.  The cast iron did start to glow red at the end.   But when I got to the middle of the crack the crack was much tighter and didn't go through the cast iron all the way.   And I couldn't get the cast iron to glow red.  Even the four burner cutting torch couldn't heat it up enough.  Plus I the closer I got to the meat of the vice jaw it became harder and harder to heat.  No doubt the mass of the vice jaw was acting like a heat sink sucking all the heat away.

A bigger torch would have definitely helped.   Let's blame it on the torch.  

I feel good that the worst part of the crack took a good deep brazing.   The brass really got sucked into that part of the crack really well.  This will probably be strong enough for my intended use for this vice.  

In the meantime I need to by a bigger torch.  Or find my larger tip.  I know I have one.   It's not in the toolbox where it belongs and it's anyone's guess where it might be living now.   I can't even remember the last time I used the large torch tip.  I'm typically brazing sheet metal with the small tip.   The large tip is here somewhere.  Someday it will show up.


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## westerner (Apr 24, 2019)

Cast Iron is just not straightforward. SO many variables with content, impurities, surface condition, age, blah,blah blah. I think ya done good, and the comments by John.K are just what my Uncle said. If you are gonna braze cast iron, find the grizzled veteran and ask HIM what flux HE uses!


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## horty (Jun 16, 2019)

Hi Guys, I dont want everyone to think Im a no-it-all, but have done alot of brazing, about 16 years worth, almost every day,, so I'll post a few pics and also say that the flux is most important, I used a general 1/8"  or 3/16" bronze rod, with a #1, 2, 3 peterson flux, The #1 is blue can not shown, they sell small cans...
Dont use coated rods, you want to use a little of each flux as your brazing, and your surface needs to be tinned or else it will just be a glob mess and will never hold any strength, a good brazing job will be stronger than the cast iron, the part should be heated to a dull red, then only will the brazing begin..I've done hundreds of brazing jobs and never had a return for any reason,,,
anyway, if you need any help just let me know, Brazing will be an lost art soon and it would be nice to teach others to keep it going, and there 
is some money to be made for a good man that can braze.

Notice that I ground the brazed weld, but is not necessary, its just for looks.


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## RJSakowski (Jun 16, 2019)

Not an expert on cast iron repair but here are a few points.  Brazing, like soldering, is best done by letting the work melt the filler.  This ensures that the work is hot enough to flow the filler into the joint.  

Also, when cast iron cools quickly after welding, it forms white cast iron adjacent to the weld which is extremely brittle.  IMO, a primary reason for preheating is to ensure that the weld area cools slowly, converting the white cast to grey cast which is malleable.  

A similar effect occurs when welding high carbon steel.  For that reason, I will preheat and/or post heat any welds to ensure the slow cooling and subsequent annealing of the weld area.


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## horty (Jun 16, 2019)

Good points RJSakowski
I always post heated the weld after, and made sure it cooled slowly.
Back in the day when we used asbestos sheets, a few bricks and a sheet of asbestos made a good tent.
Yes, there is more than just heating and slopping bronze on.


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## benmychree (Jun 16, 2019)

I have had very good luck brazing cast iron, I use bare bronze rod, prep by grinding and feather back the edges of the prep, and goop it up with silver solder flux to protect the prepared area from oxidation while preheating and brazing, and us Anti Borax EZ#3 flux during the brazing process, the bronze will wet out like solder without beading up anywhere, if I have a "secret" the silver solder flux is it, and the Anti Borax flux is the best that I have ever used, it is colored black.


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## horty (Jun 17, 2019)

benmychree said:


> Anti Borax EZ#3 flux during the brazing process, the bronze will wet out like solder without beading up anywhere, if I have a "secret" the silver solder flux is it, and the Anti Borax flux is the best that I have ever used, it is colored black.



Have never heard of those fluxes, I'm so use to using Peterson brand fluxes, and the price is right, I also use it to de-gas and remove dross just before an aluminum pour.
I'm sure yours works better, as Peterson fluxes haven't changed for 100 years..by getting a good tinning and flow it should be a sound weld.


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## benmychree (Jun 17, 2019)

The Anti Borax fluxes are a very old brand, one of their many products is forge welding flux, still available through blacksmith suppliers.
https://superiorflux.com/anti-borax-fluxes/


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## horty (Jun 17, 2019)

benmychree said:


> The Anti Borax fluxes are a very old brand, one of their many products is forge welding flux, still available through blacksmith suppliers.
> https://superiorflux.com/anti-borax-fluxes/


I have a casting to work on in a week or two, Its hard to make a change since I have enough peterson flux to choke a horse, I think I might just try it,


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## RobertHaas (Jun 18, 2019)

The OP said he had a smithy forge. If it were me, I would tin some more brass onto the area he has already brazed to get it high and proud above the crack. Then fire up the forge with the piece inside it as it comes up to temperature and "sweat" in the eisiting brazing to insure a proper bond was achieved, then turn the forge off and let the piece anneal back to room temperature over the next 3 to 4 hours.


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## horty (Jun 18, 2019)

*Thats a very good way*,,, 
Not saying anything bad about Robo Pi, but the integrity of that weld just might no hold up...most of the brass is just sitting on top.

Practice, got to make sure its a dull red preheating, and because its a small crack does not mean to use a small tip, you will loose heat to fast, need a bigger tip to keep it hot and kinda wipe and smear the fluxed rod until it flows, (tinning) then you will have it..
I have a habit of brazing the part in a angled vertical position or from the bottom up, that way your brass will roll out untill you have it tinned then it will flow, reduce your heat a bit by moving tip away and get a shelf of brass formed, then just keep building on top of that, you will then have a good sound weld. 
Its hard to really explain how to do it,, I bet if you watched it being done at a welding shop, looking over the welders shoulder, you would say "I Think I Got It" Then a little practice and you'll have it..
Everyone has a different way of brazing.


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## Robo_Pi (Jun 18, 2019)

horty said:


> Not saying anything bad about Robo Pi, but the integrity of that weld just might no hold up...most of the brass is just sitting on top.



Actually that's not the case.  The first half of the crack brazed up very well with very deep penetration.  I was very pleased with the first couple inches.   Unfortunately I had to stop at that point to reposition the workpiece in the vice.  And during that process  it cooled down a bit and I wasn't able to get it  back up to a reddish glow at that point.  So yes, the latter part of the job did not achieve good penetration.   In some places it did, but in other places all it would do is ball up on the surface.    So clearly those spots were not good.  But I'm very happy with the repair overall.   The first couple inches that went very well was probably good enough for this repair even if I had stopped there.

I don't believe that I had a flux problem.   I used coated rods, but I also dip them into additional flux.   The main problem I had at the end was not being able to get it hot enough.   I think part of the problem at that point was that the crack was getting closer to the mass of the vice jaw and that was acting like a heat sink.   I think I would have been just fine with a hotter torch.   Lack of heat at the end of the job was the most likely culprit.  It just refused to glow red at that point.   And I know that's not going to work, but I didn't have a bigger torch.   So I just let it go at that point.   Like I say, the first couple inches went really well.   So well, that that alone was probably a sufficient repair anyway.   I feel pretty good about it.  It's not a perfect repair, but I think it will do the job.   A hotter torch is what I needed.   I have a bigger torch around here somewhere but I haven't found it yet.  It's not where it belongs so where it might be is anyone's guess. 

I have a cast iron tractor pulley that needs to be brazed up next   I'm going to either find my larger torch or pick one up somewhere.   In fact, I have an old set of oxy-act torches that have larger tips.  I think the torch body needs new O-rings.  I'll have to look into refurbishing that old torch.


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## horty (Jun 18, 2019)

Robo_Pi said:


> Actually that's not the case.


Sorry, didnt mean anything Bad, at my age somethings aren't as they appear, 
Thanks for setting me straight.
Tim


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## Robo_Pi (Jun 18, 2019)

No problem.  I just wanted to clarify that it wasn't as bad at it might have sounded.  I'm happy with the repair.  It's just not perfect.   And I do like for things to be perfect.  But let's face it, they seldom are.


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## brino (Jun 18, 2019)

horty said:


> the flux is most important, I used a general 1/8" or 3/16" bronze rod, with a #1, 2, 3 peterson flux, The #1 is blue can not shown, they sell small cans.......................Dont use coated rods, you want to use a little of each flux as your brazing, and your surface needs to be tinned or else it will just be a glob mess and will never hold any strength,



@horty 
Hey Tim, how do YOU use the three different fluxes?
1) Is it a fixed ratio mix used thru-out the braze process?, if so what's your recipe?
2) Do you use one type for "tinning" and then another during filling?
3) is ther some visual trigger that makes you switch between them?

Thanks for any additional pointers.

-brino


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## Silverbullet (Jun 18, 2019)

cbellanca said:


> I have done both. I depends on how much stress the part sees in service. As thin as the part is stick welding would be at real chore with an AC welder. Getting the heat right presents an undercutting problem. Brazing is much easier.  I would follow the prep, preheat and cool down advice above for ether process.  I don't think a hole at the end of the crack will help in this case.


The main reason for the hole is on cast iron parts when there in temperature changes like a car exhaust or cylinder head. The thought on that is the expansion and contraction of the two metals , from my understanding.


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## horty (Jun 19, 2019)

brino said:


> @horty
> Hey Tim, how do YOU use the three different fluxes?
> 1) Is it a fixed ratio mix used thru-out the braze process?, if so what's your recipe?    *NONE*
> 2) Do you use one type for "tinning" and then another during filling?   *YES & NO, Us #1 Blue Most Of The Time.*
> ...


I'll do the best I can, haven't felt well for a few day, old ticker problems..

No special recipe.

During tinning, I will use a little of each, just a touch on the rod, sometimes the impurities in the cast will cause problems tinning, so to be sure the tinning takes place, It's a habit for me to use a little of all three.
You can tin the area to be welding all at one time if you want, or just go ahead a little bit, I usually go ahead a little bit and then do some filling, then some of that process is done, then you can concentrate on filling that area, if at any time you see that the brass is not flowing smoothly, a touch of all should take care of the problem.

If you see the part is cooling down to fast, heat it back up, I always use a big tip, bigger than you would think for some parts, that way the heat is always there, and by manipulating the temp at the tip, (which is done constantly, for me, by and moving the flame quickly in and out of the area also controls the heat/temp. What ever you need to do to keep a nice red heat or close to red heat and to keep the brass flowing nicely, dont try to fill a spot that wont tin, its possible to cover that area up to not be seen with brass but there will be no tinning underneath, I just concentrate on the area I'm filling.

Use to weld 4 ft cracks, 3" wide after ground out, in giant earth moving equipment transfer cases, what a very hot job, sometimes face shield would melt and face would blister, that was in the early 70's,  but then It was hard to find anyone to do that type of work, so $4-5 thousand dollars was nothing to an oil field company for 2 days work, when the new part was 15-25 thousand dollars and 2 months to get it from overseas.

That's about it, and don't breath in the fumes to much, could cause some health problem, for me it made me drink alot of cold beer after a days work, or if I had sore arms and shoulders I would rub alcohol on them from the inside out.

If somethings don't make sense to you I apologize, this is the best I can do considering how I feel.

If you trust me and want to send me your private email, I might have some stuff to send you...

Hope this helps you
Have a good day,
Tim


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## cbellanca (Jun 19, 2019)

Silverbullet said:


> The main reason for the hole is on cast iron parts when there in temperature changes like a car exhaust or cylinder head. The thought on that is the expansion and contraction of the two metals , from my understanding.


The reason to place a hole at the end of a crack is to reduce the stress concentration to reduce the possibility of the crack continue to grow.  Once a crack is properly repaired by welding or brazing there is no need for a hole. I have weld repaired cracks in steel castings and forgings some up to 8" thick and have never used a hole at the end of a crack once  it was properly repaired.


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## john.k (Jun 19, 2019)

The best way to do pulleys is to use a single burner gas stove for preheat........turn it up ,and have a tin shield around the stove.....a 5 gallon drum is good.........generally quite big pulleys braze easy with this much extra heat.......then you dont need a giant oxy torch,just a big one...................and remember.....grinding can smear the graphite.


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## Robo_Pi (Jun 20, 2019)

Here's the brand new cast iron brazing job.   It's a front motor pulley on an antique Case SC tractor.    This pulley has been loose and wobbling for years.   It has a bolt that goes through the pulley and the crankshaft.  I have no clue if that is factory design or if someone bolted this on and some point.   In any case, you have to take the whole front end of the tractor off to repair it.  So that's why I let it go for so long.   But now it needs to be fixed.    The pulley wobbles terribly and is an extremely loose fit.

The following photo shows the pulley on the crankshaft.   The bolt that used to hold it on broke off and is missing entirely.





This next photo shows the crankshaft with the pulley removed.   I'm absolutely astonished that the crankshaft doesn't appear to be damaged at all.  I was expecting to find a totally out-of-round chewed up nub.   But the shaft actually looks pretty doggone nice.  So no problem there.




Here's the removed pulley.    Notice the chewed up shim that was in it.   Apparently that's what saved the crankshaft from being damnaged. This shim appears to have taken the brunt of being chewed up.





Here I have removed the shim from the pulley.   The pulley itself is pretty chewed up inside.  Not nearly as bad as I was expecting.  But I'll definitely bore this pulley out to clean it up a bit.





The following shot shows how the bolt elongated the holes.  Originally this was just a hole,  not a slot. 

You can also see where the bolt has basically eaten away and most of the pulley flange.





The other side didn't get chewed off quite as bad.






I found an old piece of gas pipe that fits pretty well.  I think I'll use t his for the new shim. 

I know the pipe looks pretty bad, but I think I have a cleaner piece around that I'll actually use.




Here's my current plan of attack. 

1. Bore out the pulley to just fit the gas pipe. 
2. Grind down the elongated bolt holes.
3. Insert the gas pipe into the pulley and have a brazing bonanza.
Fill up all the elongated bolt holes while allowing the gas pipe to also be brazed into the pulley.
4. Face off the finished assembly.
5. Put it back in the lathe and bore out the inside of the gas pipe to the correct diameter to fit back on the crankshaft. 
6.  Re-drill a new bolt hole.
7. Bolt the pulley back on the tractor.

And if anyone asks I'll just pretend that I don't know who the idiot was that fixed it.

How's that sound?


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## brino (Jun 20, 2019)

==============Off-Topic Warning!===============



Silverbullet said:


> The main reason for the hole is on cast iron parts when there in temperature changes like a car exhaust or cylinder head. The thought on that is the expansion and contraction of the two metals , from my understanding.



@Silverbullet,
We haven't seen you for a while.
Glad to see you posting again!

-brino


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## brino (Jun 20, 2019)

Robo_Pi said:


> How's that sound?



It sounds to me like you have a solid plan!
-brino


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## brino (Jun 20, 2019)

horty said:


> Hope this helps you
> Have a good day,
> Tim



Thanks for the extra info Tim!
-brino


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