Brazing cast...??? (follow-up thread)

BigTone

Member
How difficult is it to braze cast iron? Do you need to be experienced or is it something a newbie can do? The crack is underneath the tractor, do you have to braze from the top down or can you climb underneath and braze it from laying on the ground? Thanks folks, just trying to educate myself before I begin any serious teardown...~Anthony
 
Tone it can be done we did it restoring an H. Found the housing
was cracked under a bull gear in the tranny. Had to drain the oil
split the tractor then invert the housing. Got a gurru local metal
worker who used a small grinder to open the crack then braze it.
with the heat it would run so chased it with the grinder and braze
until it stopped. This has held up with no problems. It was a big
job but easier than changing the housing.
 
There is a special powder flux for brazing cast. It is red/rust colored. Normal brazing flux is white. A welding supply company should have it.
 
Upside down brazing is neither fun nor reasonable for a good welder. There are really good cast iron welding rods available from a welding supply store (not the normal ni-rod, which does work in some cases, but this material is much better) It is also not an amature welder rod. Your issue is going to be getting the oil out completely. Welding, brazing, or JB weld, do not work when oilyconditions are present.
Were it mine, I would use metal stitching. It is a process that uses overlapping metal plugs to seal the crack. In your case (no pun intended) the crack is not structural, so the integrity of the housing will not be affected. I would purchase black iron 1/8" pipe plugs (for natural gas service) from a hardware store and (with care to start at the very beginning of the crack) I would drill and tap a series of plugs into the housing. Each plug must be tightened in with locktite to prevent leaks and turning. The square head on the plug is then ground off and made flush with the housing. The next plug is then driled and installed overlapping the first, and aligned with the crack. continue in this along the crack until the end has been reached. grind off the last plug to match the housing and smooth with a flap wheel or body file. Stippling the smoothed area with a dull center punch can immitate the sand pattern of the casting. Paint and fill. Jim
 
That sounds like something I could do but I'd be afraid of doing more damage, to the point where a braze/weld wouldn't fix my screw up if I drilled crooked, wrong, didn't overlap correctly in some way. I just don't know which way to go, if the bearing that fell out requires transmission work then I might as well break it all down, clean the heck out of it and braze/weld. If I can get the ball out, replace the bearing, and there are no broken rear end gears than the stitching might be the way to go. should I just pull the trans cover and see what I'm working with before i go further? Will I see what I need to see? thanks Jim, ~Anthony
 
(quoted from post at 10:06:55 07/15/14) That sounds like something I could do but I'd be afraid of doing more damage, to the point where a braze/weld wouldn't fix my screw up if I drilled crooked, wrong, didn't overlap correctly in some way. I just don't know which way to go, if the bearing that fell out requires transmission work then I might as well break it all down, clean the heck out of it and braze/weld. If I can get the ball out, replace the bearing, and there are no broken rear end gears than the stitching might be the way to go. should I just pull the trans cover and see what I'm working with before i go further? Will I see what I need to see? thanks Jim, ~Anthony

If you have not corrected the transmission issue then you need to stop and pull it apart before you cause more damage.
 
I have done more than one by overhead brazing, but it is not a job that most can do. You will need many hours of brazing different positions before you try overhead. At my age (71) I would not try it again.
 
Many moons ago i bought an old M to put under my
cornpicker. It had a lead patch over a hole on the
rear end housing. It had a whole lot of holes
drilled and threaded for 1/4 inch bolts. It took
to leaking so had a friend (excellent cast welder)
weld it up for me. I drained the grease and and
kept the cast warm with a trouble light for a
week to 10 days before Doug did his magic. Too my
knowledge its still going with no leaks. He used
some kind of speciality rod not the normal cast
rod. This was 25- 30 years ago.
 
I know brazing cast will work and hold really well, but you will need to take the part off and do it upright. We had the lower sprocket of a gathering chain on an IH chopper row head that kept breaking. IH dealer was many miles away and we finally took the pieces, ground a bevel in them, heated the whole gear up with the big budd torch tip and brazed it back together. that gear lasted the rest of the season and don't know how much longer... lasted longer than any of the new parts. Had 50 acres of corn, broke 2 or 3 in less than half and the repaired part lasted the last 25 or 30 acres.
 
Brazing works basically like soldering, if you've ever soldered electrical stuff. You use an oxy/acetylene torch and a carburizing flame. You'll be heating the iron to a low red heat and using a brass alloy filler rod. You're working a molten puddle of the alloy along the crack, kind of like arc welding only much slower. Unlike the arc welding though you are not melting the parent material. The flux does the final cleaning so the filler material can bond to the parent material.

Obviously it will be necessary to have the case upside down to do a good job. If the tractor is still broken at present time, then go ahead and tear down the whole thing and clean it out. I would pull axle housings and everything.

You'll need to clean the area of paint and grease for at least 3 inches either side of the crack. I would take an angle grinder and "dust off" the casting slightly. Once you can see how far the crack goes, drill out the ends with a 1/4" bit to help stop the crack from propagating. You'll fill the hole when you braze. Then "V" out the crack a little bit to maximize the contact area of the parent material around the crack. Use brake cleaner and clean the heck out of the area on both sides. Cast iron is porous and you'll want it as oil free as possible.

I would round up some kind of burner, like from a turkey fryer or old bathroom stove or something and get it going under the case when ready to braze. This is just to take the chill out of the whole casting. About like touching a car on a hot summer day. Then I would do the actual brazing.

There's bound to be some you-tube videos of people brazing. Watch some of those and do some google searching. Older welding and farm maintenance type books usually had sections on brazing. Hit the local library and see what you can find.
 
Repairing the bearing will require removing many of the components that need to be removed to braze it. It could be brazed from inside, thus further reducing the visual impact of the break.
You will be removing one bull gear and axle to replace the bearing. Removing the other bull gear is pretty easy at that point. I would braze it from the inside during the repair.
Stitching is still an option. there is no real difficulty in doing it, and you can do it your self. Practice on a junk block from the scrap yard to get the feel for stitching. Jim
 

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