Metal casting furnace

Friday 15th May 2015

My aim this year is to cast my own bronze sword, and to do that I need to melt the bronze. I just made a bucket furnace that's good enough to melt copper and tin, the metals in bronze alloy. My furnace is based on the Mini Metal Foundry on Youtube.

Ingredients

Here are ingredients to make it.

  • 10 litre metal bucket - the body of the furnace
  • 5 litre plastic bucket - to make a void in the centre of the furnace
  • 15 litre plastic bucket - to make a lid for the furnace
  • Tin can - to  make a void in the centre of the lid, to release pressure
  • Two metal hoops - these will become handles for the lid
  • 1 inch steel pipe - this is the air intake for the furnace
  • 25kg dense castable from Castree Kilns
  • dog - serves no useful purpose

 

Making the lid

First of all I made the lid, with 10kg of the dense castable and 1.3 litres of water, mixed thoroughly.

I set the tin can in the centre of the mix and sunk the handles into it. Then I let it cure for 48 hours. The dense castable material is strange stuff, it's very dry and at first I didn't think it was going to cure. But 48 hours later it's hard as rock.

 

Making the body

I needed to make a hollow body for the furnace, so I used a small bucket filled with water in the centre to make the void.

I used 15kg of dense castable with 1.95 litres of water, which pretty much filled the bucket. I let this cure for 48 hours as well, and spent several hours cleaning all the gack off the kitchen table, floor and ceiling.

The mistake I made here was spilling some of the dense castable into the white bucket in the middle. When I poured the water out, there was a 2cm layer of rock hard material in the bottom - turns out it sets underwater just fine! I hacked it into little pieces and pulled it out with no problems.

Once it had set, I used a hole saw to cut a piece out of the side, and fitted a steel pipe to force air into the furnace. This is hooked up to Kat's hair dryer - shh, don't tell her!

Here's the finished furnace, the next step is to fire it up!

Here are some pics of the first time I lit it up, to melt some aluminium as a test. Aluminium melts at a much lower temperature than bronze, so it's easier to work with and cheaper.

The crucible is made of ceramic bonded clay graphite, it's a Salamander A2 from Castree Kilns. It's rated to 1600°C. The original instructions I followed used an old fire extinguisher, but I've been told that these are quite unreliable and prone to sudden failure.

Finally here's a quick video of the furnace in action:

The next step is to make a sword template out of wood and then cast it.

I've no idea how that works but it's going to be fun finding out!

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