Quick cast iron question

Dimner

Named Man
A couple weekends ago I bought a couple cast iron pots at the flea market. One that holds 40 or so lbs of lead and another that holds probably over 70.

Problem is, that when I bought them they were nested together, so I didn't notice the perfectly drilled hole in the bottom of the bigger pot. It's probably a 1/4".

So, short of welding (which i do not have the skill or equipment to do), anyone have any ideas on the best way to plug this hole so it can be used to smelt lead?

If welding is the only option, is there a specific type of welding that would work best?
 

Rick

Moderator
Staff member
Nickel rods will weld cast iron. Were it me and they would only be used for smelting I would probably just put a bolt and nut in the hole.
 

Joshua

Taco Aficionado/Salish Sea Pirate/Part-Time Dragon
If you put a light counter sink on the bottom, a carefully peened rivet could be made flush to the bottom of the pan.

You would need to be mighty careful with the hammer and have the rivet backed up by something solid.

When I was a teenager I tried to straighten a warped cast iron pan with a hammer. Well cast iron will crack rather than bend when hit. I destroyed a that pan.
 

Tomme boy

Well-Known Member
Put a bolt in it if you can. Add a flat washer to each side to help seal it. I had a pot that was cracked from the top ring to almost the middle of the bottom. I drilled a hole to stop it from cracking any farther. Then put a machine screw in the hole. Even though it was cracked it never leaked any lead out. So you should be good.
 

Bret4207

At the casting bench in the sky. RIP Bret.
If you know someone who can braze, that is an option. A copper rivet would be a perfect answer if you can source a hunka copper 1/4" in diameter. A steel rivet will likely work too, but it's going to rust and expand/contract at a different rate than the cast. Probably not a big issue, but copper would be my choice.
 

Ian

Notorious member
I'd be afraid that swelling something in the hole would stress the bottom and cause radial cracks. Copper and brass have a much higher coefficient of expansion than cast iron.
 

Dimner

Named Man
Thanks everyone.

Going to the hardware store this afternoon. I'll see what they have on hand that might be able to fix it. Hopefully a brass bolt, but I'm probably not that lucky given the diameter of the hole. Worst case, I will drive around town with my sad rusty cauldron and hit of some metal fab/welding places. With some cash in my pocket and a 12 pack of beer in the jeep.

If I do end up using a stainless bolt, I will make sure it's not a tight fit.
 
Last edited:

Rick H

Well-Known Member
My understanding is that cast iron can be welded, but that it takes an oven (kiln) to preheat it and then cool it down in steps afterward or the stresses will destroy it. I think the stainless bolt with washers makes a lot of sense.
 
  • Like
Reactions: Ian

Bret4207

At the casting bench in the sky. RIP Bret.
I'd be afraid that swelling something in the hole would stress the bottom and cause radial cracks. Copper and brass have a much higher coefficient of expansion than cast iron.
Lotsa hog kettles and dutch ovens up here repaired just as I outlined. Maybe at lead alloy temps you could be right, but the copper being so much softer I don't think it's an issue. Only one way to find out...
 

Bret4207

At the casting bench in the sky. RIP Bret.
My understanding is that cast iron can be welded, but that it takes an oven (kiln) to preheat it and then cool it down in steps afterward or the stresses will destroy it. I think the stainless bolt with washers makes a lot of sense.
No, oven's not needed. I preheat a large cast 3 pt lifting attachment for one of my cralwers by positioning a propane cook stove under the item. It weighs about 250lbs. Just had to leave the stove going for a couple hours to get it hot. I've also used a large propane weed burner to preheat cast. Just have to let it cool nice and slow.
 

KeithB

Resident Half Fast Machinist
I've welded cast iron with a high Nickel content rod using a basic AC stick welder. (A Lincoln 225 buzzbox.) The rod was called Nirod, don't know the manufacturer. Didn't seem that hard. Preheat, weld, post heat and slow cool. The rod contains an element (don't remember which one) that prevents hardening at the base metal/weld zone. The rod was so expensive they sold it by the rod, not the pound!

Here is the dilemma: (a) Weld it up and risk having it crack again from a poor weld job, or (b) plug the hole with something and risk having stress cracks form at the hole. Remember lead is what 13.6 times heavier than water? and that melting it occurs at temperatures much higher than boiling water. Your hog scalding pot cracks and it puts out your fire, Your smelting pot cracks and I'll let you imagine the consequences of 70 pounds of 650 degree liquid flowing unrestrained around you...

I'd give it to my wife as a planter and get something a lot safer to use. But I'm old and cautious.
 

Dimner

Named Man
I'd give it to my wife as a planter and get something a lot safer to use. But I'm old and cautious.

I'm thinking that might have been what this pot was used for. Pitted something awful on the inside. I may end up giving it to her if my tests do not go well. I found that an m6 stainless screw fits it perfectly without being too tight. I'll do some test heating and cooling to see how it reacts.

But if it fails, where and what do I look for that can hold 60+lbs of lead for alloy blending?
 

Bret4207

At the casting bench in the sky. RIP Bret.
Keith makes a good point.

You can get a no name 5 qt cast iron "dutch oven" (incorrect ID) off Ebay for about $25.00. Larger ones are available too. Or try this place-https://www.agrisupply.com/cast-iron-cooking-supplies-utensils-kitchen-accessories/c/6200000/pgnum/2/
 

Dimner

Named Man
The smaller pot I'm using is a 6 quart Dutch oven. Looking for something about double that size. If you guys know of any places, I'd appreciate the help.
 

blackthorn

Active Member
I'm thinking that might have been what this pot was used for. Pitted something awful on the inside. I may end up giving it to her if my tests do not go well. I found that an m6 stainless screw fits it perfectly without being too tight. I'll do some test heating and cooling to see how it reacts.

But if it fails, where and what do I look for that can hold 60+lbs of lead for alloy blending?

Cut the top off a 20 pound propane tank. Just screw out the filler valve, fill the tank with water, use a zip-cut to cut a bigger hole around where the valve was, dump the water, lay the tank on its side choose the depth you want and use the zip-cut to shorten the tank. You can even make a spout in the top of the rim and attach a large washer on each side with a fabricated lid like I did. The washer I have use a i+ inch hole and I can run a one inch steel bar through them to allow the rod to sit on automotive stands. This relieves the force of the weight of many pounds of molten lead on my heating unit.
 

Tomme boy

Well-Known Member
Don't need water to flush a propane tank. Take valve off and turn the tank upside down. Propane is heavier than air so it will fall right out of the tank. If you want to make sure flush with water after letting the tank sit for a day upside down. I use them for is for making little wood stoves. Cut up over 10 so far with no problems. Only ever flushed the first one.
 

Bret4207

At the casting bench in the sky. RIP Bret.
The smaller pot I'm using is a 6 quart Dutch oven. Looking for something about double that size. If you guys know of any places, I'd appreciate the help.