Cast Iron Repair | GTAMotorcycle.com

Cast Iron Repair

bakaboy

bakaboy

Old, Slow and Grumpy
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Some of you know that I enjoy my late winter maple syrup boil.

Historically we boiled with cast iron cauldrons. My old one gave up the ghost years ago due to cracking.

For recent years I boiled in an open steel pan.

I found 2 good shape cast iron kettles last year. I used 1 of them and also my pan.

The kettles are faster.

So I want to use my 2nd kettle this year.

But someone drilled a hole in the upper edge about 3 inches from the top.

It wont be in immersion or indirect contact with the flames. But syrup will likely well up to the spot and will spill out.

The hole is about 0.25 in diameter.

I thought about trying to find someone to puddle weld it with brass but was wondering about a polymer plug.

Anyone with any knowledge?
 
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I would braze it shut. Alternatively, tap it and run a bolt in to plug it. I have no idea about polymer plugs. Presumably you could drive one in but depending on your heat source, the exposed end could get quite toasty. Nobody wants melted plastic in their syrup.
 
If you want to try a polymer solution, cut a chunk out of a silicone spatula and jam it in the hole. You won't easily get a better polymer solution as it's flexible and reasonably heat tolerant (400+F).
 
JB will fix cast iron.

If you don't want to tap the hole, use an undersized carriage bolt & nut with a copper or silicone washer.
 
Mad Mike said:
JB will fix cast iron.

If you don't want to tap the hole, use an undersized carriage bolt & nut with a copper or silicone washer.
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How small do carriage bolts come? His hole is only 1/4". Any carriage bolt I have seen will have far too large a square and I'd worry about cracking the pot.
 
Maybe a pic would help people visualize the issue better @bakaboy. My simplest solution / mitigation would be to see if it can be filled with less syrup so it doesn't even well up to that spot (but I know nothing about maple syrup).
 
GreyGhost said:
How small do carriage bolts come? His hole is only 1/4". Any carriage bolt I have seen will have far too large a square and I'd worry about cracking the pot.
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You can get 3/16 bolts, it only takes a minute to file off the square under the head.

Another option is to drop into an electrical wholesaler and pick up a 1/4" copper rivet. These are soft and can be peened with a small hammer.

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mimico_polak said:
Maybe a pic would help people visualize the issue better @bakaboy. My simplest solution / mitigation would be to see if it can be filled with less syrup so it doesn't even well up to that spot (but I know nothing about maple syrup).
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I will snap a picture when I am at the shop next. I brought it south to be warm for whatever repair method I decide to use. Didnt want to be trying to fix cast iron sitting at -10C.

It is a deep kettle so my default can be to just have less depth and hang the pork fat lower.

And since questions will come from that....the syrup boil will cycle in boil height and it will well up. So by hanging the fat the syrup will rise till it touches the fat and immediately cascade back down.

I do not know the physics of why.

I learned the step from my grandfather.
 
As above, brazing will work.

I also just welded up a crack in a cast iron manifold on my truck. My Uncle was a welder at Bombardier for 35 years and advised me to..

- preheat the part with lots of heat. Heat the whole casting (if possible) to between 500-800 degrees F. I used the oven while the wife was out
- use a nickel-type electrode
- use a fairly low current
- stitch weld if the bead stretches over a long area
- Let cool slowly (I also used the oven and slowly reduced temperature although I guess you could bury it in sand or lime)

My crack was about 3 inches so i used 1/2 stitched. Came out looking fine. We'll see how it holds up over time
 
bakaboy said:
I will snap a picture when I am at the shop next. I brought it south to be warm for whatever repair method I decide to use. Didnt want to be trying to fix cast iron sitting at -10C.

It is a deep kettle so my default can be to just have less depth and hang the pork fat lower.

And since questions will come from that....the syrup boil will cycle in boil height and it will well up. So by hanging the fat the syrup will rise till it touches the fat and immediately cascade back down.

I do not know the physics of why.

I learned the step from my grandfather.
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The fat breaks the surface tension of the bubbles.
 
not food safe , just non toxic. My concern with putting a different type metal bolt in the hole , could it expand faster than the cast iron and turn a hole into a crack? I think I would take it to a welding shop and have it puddled if you dont have that gear.
 
crankcall said:
not food safe , just non toxic. My concern with putting a different type metal bolt in the hole , could it expand faster than the cast iron and turn a hole into a crack? I think I would take it to a welding shop and have it puddled if you dont have that gear.
Click to expand...

That’s a distinct possibility. What about a silicone cork?
 
crankcall said:
not food safe , just non toxic. My concern with putting a different type metal bolt in the hole , could it expand faster than the cast iron and turn a hole into a crack? I think I would take it to a welding shop and have it puddled if you dont have that gear.
Click to expand...

The last puddle weld try on my original cast iron snow balled as the puddling process deteriorated the surrounding 100 year old cast iron graphite.

I am thinking maybe the idea of the copper bolt that is smaller diameter than the hole itself and peened off to surface.

If it isnt 100% sealed the weeping sap might charcoal and finish stopping the leak.

While the copper plug and cast iron should have similar expansion/contraction while the copper shaft is not 100% the same diameter of the cast iron hole (thus less chance of crack)

I have yet to test this kettle under stress. It shows well but they can split if there is unseen graphitic corrosion and it sees some heat.
 
Copper bothers me due to oxides and dissimilar metal corrosion. I'd go with with an unplated 1/4" steel bolt with silicone washers. Are we taking bets or is this a poll?
 
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