Basic Homemade Foundry Furnace Plans

Don't let the image scare you. Having a melting furnace is basic actually. There are plenty of homemade foundry furnace plans that you can use to build your very own DIY steel foundry.

Depending on if you want to use propane or coal, you may have to adjust how you build your furnace, but the steps below should get you well on your way to learning how to make a mini metal foundry!

These homemade foundry furnace plans will teach you how to fabricate the furnace, a lid, the crucible, and a table or stand that is needed to lift it all up off the ground. Feel free to adjust the sizes to your specific needs or follow exactly to be sure of success.

Tools

There is a simple list of tools you will need to complete any of the homemade foundry furnace plans you may come across. This design requires:

2.5 Qt plastic bucket
10 Qt Steel Container or Bucket with an open top
5 qt big mouth plastic bucket
Large plaster mixing bucket
Air supply
Steel pliers
1 cup measuring cup
1” drill bit
3” drill bit
Handheld power drill
Hand saw

Materials

You will also need these materials to insulate the furnace that you are planning to make and providing the air flow that you need into the foundry.

Plaster of Paris
Play Sand
Water
A depressurized fire extinguisher or other 3" wide steel container
1” steel air flow pipe
1” PBC pipe
1” PBC coupling
2 metal handles or U-Bolts large enough to be set in plaster and used as handles for the lid
Tripod with a flat top or 3 welded on legs to lift it off the ground

Furnace

The first step in your homemade foundry furnace plans will be to measure and mix the plaster of Paris and sand you are going to use to build the insulating layer between your crucible and the steel container.

1
Use the 2.5 Qt bucket to measure out 1 ¾ buckets of plaster, 1 ¾ buckets of sand, and 1 ¼ buckets of water into the mixing bucket.
2
Mix well by hand, making sure all the plaster and sand is wet, and there are no lumps in your mixture. This stuff sets up fast, so be sure to work quickly.
3
Carefully pour the smooth liquid into your steel container.
4
Gently submerge the 2.5 qt bucket in the still liquid plaster mix to create a deep well large enough to hold the crucible. The plaster should rise as the bucket is inserted but should not overflow. You will want this well to be centered within your furnace, so shift the inserted bucket around until it is even on all sides and flush with the top of the plaster.
5
Hold the bucket in place until the plaster has set enough to hold the bucket in place. This step will take about 15 minutes.
6
Use water and a rag to clean up the container from any loose plaster, and to clean up the exposed edge of plaster for a cleaner finish.
7
After about an hour, use the pliers to remove the bucket, and you should be left with a deep smooth well perfect for the crucible.
8
Drill a 1” diameter hole high up on the bucket for your air flow pipe. Continue to drill through the plaster at a 30-degree downward angle, to allow the pipe to sit at a slant going down into the furnace. This will prevent any metal from leaking out of the pipe if your crucible does not hold up.
9
Insert steel Pipe, attach it to the air flow pipe, adding the PBC coupling and pipe for enough length to reach your air supply.

Lid

Homemade foundry furnace plans often require a lid, as this will help the furnace get hotter faster, and will help it retain heat longer.

1
Measure 10 cups plaster, 10 cups sand, and 7 cups water into the plaster mixing bucket. Mix until smooth and even.
2
Pour carefully into 5 qt wide bucket.
3
Immediately set in U-Bolts or handles deep into the setting plaster, far enough apart to leave room for 3” hole in the lid.
4
Once the plaster is set, about 1 hour, remove the lid from the bucket.
5
Drill a 3” hole in the center of the lid, which will be the same size as your crucible.

Crucible

A crucial part of your furnace plan is the crucible you will use to melt the metal. It should be made of steel, and comfortably fit inside your furnace surrounded by coal.

1
Saw the top off a steel fire extinguisher or other 3” round steel container. 6” or taller will be a good size, you just want to make sure it is not as deep as the well you made in the furnace, but big enough to hold the amount of molten metal you want to melt.
2
Clean up any sharp edges with a metal file and it is ready to use!

Table or Stand

Any stable table or stand will work to lift the furnace off the ground, but you want to get something that is a tripod. Three legs are much more stable than four, so you can rest assured your new homemade furnace won’t wobble while you are melting metal.

If you know how to weld, you can attach legs of your own design to the bottom of your furnace. This might be a great time to learn a new skill!

Plaster of Paris takes about 24 hours to completely harden, and you don’t want to use your new furnace until you are sure it is completely dry. Once its ready, put your furnace on the stand, place the crucible in the center of the furnace. Start your fire with kindling and add the coal around the crucible. Turn on the air supply and put the lid on. Once its warm enough, add your metal to the crucible, and you have yourself a successful homemade foundry furnace!

That is about everything. I hope you enjoyed the article, and if you having any questions about using your tools and equipment, please visit that section.