Cast iron brazing questions (with photos)

[jbaccell]

IMHO, drilling the holes is good advice and will prevent the crack from migrating.

 

[pontiac428]

I was told years ago to drill a 1/8" hole ( and do ) at the both ends of the split to avoid the split from continuing. What are your thoughts on that practice ?.

It does work, except the time I tried it on a growing crack on my windshield. Just kidding. It's considered best practice for castings, at least it's in all the old books. Castings are brittle, and heat cycling can force the cracks to grow, but I suspect any kind of weldment will reduce the stress on the crack significantly by supporting the base and holding things in place. So I've always reserved a little bit of snake-oil doubt over the drilling, but it does certainly interrupt the path of the crack on the micro level. It depends on the repair. Big stuff, definitely. Exhaust manifolds and thin stuff, nah, too small and you'll never know where the end of the crack really is. So many ways to approach a cast iron repair, so many work, it's hard to draw a line where one is better without really looking at the specific part. For your part, I would avoid heat since the part is precision sized and you cannot clean up any warping when you are done without losing that precision.

 

[ltlvt]

When the crack is in something like an engine block or a pump casting this is the correct way, If it is not a crack but something like an ear broken off it is not necessary.

 

[ltlvt]

It does work, except the time I tried it on a growing crack on my windshield. Just kidding. It's considered best practice for castings, at least it's in all the old books. Castings are brittle, and heat cycling can force the cracks to grow, but I suspect any kind of weldment will reduce the stress on the crack significantly by supporting the base and holding things in place. So I've always reserved a little bit of snake-oil doubt over the drilling, but it does certainly interrupt the path of the crack on the micro level. It depends on the repair. Big stuff, definitely. Exhaust manifolds and thin stuff, nah, too small and you'll never know where the end of the crack really is. So many ways to approach a cast iron repair, so many work, it's hard to draw a line where one is better without really looking at the specific part. For your part, I would avoid heat since the part is precision sized and you cannot clean up any warping when you are done without losing that precision.

I 100% agree with you. There is just not a cookie cutter that works on every job.

 

[aliva]

I've drilled some castings in the past before welding, seemed to work

 

[murraym]

If you do not have and Carbon Rod to use as a plug, i would try what you are attempting except that i would machine a bush to fit the hole rather than use a solid piece of steel. that way when you are done brazing, you'll have a good bore to indicate from and machine the bushing out when the braze sticks to it.

 

[Charles scozzari]

If you do not have and Carbon Rod to use as a plug, i would try what you are attempting except that i would machine a bush to fit the hole rather than use a solid piece of steel. that way when you are done brazing, you'll have a good bore to indicate from and machine the bushing out when the braze sticks to it.

The machine shop at the shop where I worked had a welder who would braze together broken parts with a piece of steel if the repair was missing the part that was cast iron. I have never seen or heard of any problem arising from his repairs.

 

[murraym]

The machine shop at the shop where I worked had a welder who would braze together broken parts with a piece of steel if the repair was missing the part that was cast iron. I have never seen or heard of any problem arising from his repairs.

i agree that brazing steel and cast would work. However, If the bushing is brazed in the bore, it would need to be remachined to return the bore to the original size if that makes sense. Maybe i didn't make my idea clear?

 

[Charles scozzari]

i agree that brazing steel and cast would work. However, If the bushing is brazed in the bore, it would need to be remachined to return the bore to the original size if that makes sense. Maybe i didn't make my idea clear?

No, you did, but I just mentioned it for those who may not know. In the case of the bushing if that was the way he would go I would use a piece of tubing to make the removal easier. Charlie.