Looking for an easy build home metal foundry?
Need it affordable, capable of high temperatures and sturdy enough not to fall apart with every
use? I’m going to show you how.
Hi YouTube, I’m Geoff the VegOilGuy. Today I’m going to be building this stable,
high temperature home metal foundry to work alongside my waste oil burner, for melting
and recycling various metals for other projects. Like so many others out there, I started off
using Grant Thompson’s Mini Metal Foundry recipe and whilst I still think it’s a masterpiece,
brilliant for short term use, anyone wanting something a little more substantial should
think more carefully. You can see mine here, made with Grant’s 50/50 sand and Plaster
of Paris mix specification. The problem is this mix is just too weak. It crumbles and
disintegrates too easily and frankly I’ve got fed up of repairing mine.
Taking inspiration from Myfordboy, I’m going to be using dedicated dense, castable Refractory
mix that’s capable of withstanding temperatures up to 1700 degrees Celsius (3092 Fahrenheit).
This should be much more solid and stable. If you want to build along with me, you’ll
need a couple of bags of this. Thankfully if you shop around, it is affordable.
For the structure of the foundry, you could use Grant’s two-bucket approach or even
Myfordboy’s plastic mould approach, but I’m going to be recycle my old Foundry. It
was originally a second hand vegetable oil container and these tins are an excellent
basis for this purpose. I’ve got a spare on hand and will be using both to strengthen
this home foundry. Originally I took one of these veg oil containers
but it was much too tall. So cut out a slim centre section and used both top and bottom
to great success. Obviously it’s important to check that the
container you choose is going to be big enough to handle your crucibles. Again I’m afraid
Grant’s crucible recipe didn’t work for me, so I purchased a couple of crucibles cheaply
on eBay. Here I’m using the larger of the two to make sure I’ve got clearance. You’ll
need a good couple of inches of refractory in the bottom of your foundry, so take this
into account when measuring up. Once you cut either end from these containers,
they lose a lot of strength and don’t keep their shape. It occurred to me an ideal solution
was to reattach the thick rim I’d previously cut away. Here is an older now discarded lid,
but I’m interested in the rim which is much thicker and more structural. The angle grinder
made quick work of removing the thin top material, leaving the rim and sides intact. It was then
just a matter of sliding this down over the bottom section. To do this I needed to cut
a thin slot, again using the angle grinder. It was a tight fit, but the old lid slid over
the bottom section and could then easily tapped down to an ideal height. The metal began to
bulge where I’d cut the slot, but this could be tapped out later.
A scrap of wood helped me gauge the ideal height all around.
I then drilled and riveted the rim section in four places. Self-tapping screws or small
bolts could also be used instead. Once fixed, the whole section regained considerable
strength and I was able to tap out the slight bulge with several light hammer blows. I only
cut one slot be in hindsight three or four may have prevented this bulge.
As nothing sticks well to loose rust, I used a wire brush in my drill to roughly clean
everything. Looking around for something roughly two inches
tall, I used a hole-saw as a guide to mark a two inch high line around the inside of
the container. This is the height of refractory filling.
As the foundry will be heavy, I decided to later add some castors for easy movement,
so I bolted a simple plywood base to the container. Using the bolt means I can always detach it
if I need to. Now I’ve already cut a hole in my base. This
is the inlet for the waste oil burner, the air supply or in my case both. Grant’s tutorial
recommends using barbecue charcoal to fuel your foundry and for your first few attempts
at metal melting, that’s a good idea. But charcoal is hard to control. I found as soon
as the foundry was hot enough, the charcoal was all but burned out.
A gas or oil burner is a better way to go. The heat source is more controllable and dependable.
If you haven’t already built your burner, you should really do that first so you know
what size hole you need to cut. If you’re looking to burn waste vegetable or motor oil,
check out my waste oil burner design. This is a simple, low tech, easy build design that
generates plenty of heat using recycled waste fuels.
There are three important considerations you need to make when cutting your hole.
Firstly, as I’ve already said, make sure your hole matches the diameter of your burner.
Secondly, position the hole so that its bottom edge is at around 3 inches above the bottom
of the container. This will allow for 2 inches of refractory and an inch clearance for the
burner. Finally, don’t cut straight on to base.
Ideally you want your burner to enter at an angle to encourage the heat to flow around
the edges of your foundry, evenly heating your crucible. Reflect this angle when you
cut your hole. These containers aren’t very thick so a drill and hole-saw make easy work
of this. A few weeks back I made a new lid, but that
used a mix of my own creation. Whilst this was holding up quite well, it was still cracking
and so I decided to empty out the content and fill it with proper high temperature refractory.
It also struck me as a good idea to add a lower rim to the lid as well. The increased
strength makes the extra effort really worthwhile. And I’ve got the remains of the second container
to hand. So the former lid was cleaned up and the base
of the other container was sliced away with my angle grinder.
Grant’s crucible suggestion of an old fire extinguisher didn’t work for me, but it did
leave me with a nice steel tube to line the hole in the lid. An old food tin would do
just as well. Taking the freshly cut container bottom, I
found the centre, marked it and drilled a pilot hole.
I was then able to use the same hole-saw to cut a large feed-hole in the future lid.
A little work with a file took care of any nasty edges and the tube slid in a treat.
I cut away the flat top of the former lid as I did before and this will become the underside
of the new lid. Now the two sections of the lid need to come together.
This time I cut several slots to make fitting simpler.
Same procedure again. Tapped into place and this time I made sure that I had sufficient
height to allow for a good couple of inches of refractory. I then riveted the two sections
together – just four rivets did the job. At this point I realised the tube wouldn’t
be tall enough – typical – but thankfully an ordinary food can was an almost perfect
fit. I cut a few slots and sure enough it all went together.
I made sure there was plenty of room for a soda can… I do like to melt and recycle
these… The lid needs a couple of handles. You can
use what you like. I had some copper pipe to hand. It might not be the strongest metal
but it won’t rust and it can easily handle this job.
The pipe is flattened then bent over in my vice. It doesn’t need to be pretty, just practical.
Four rivets held edge handle in place and that completed this stage of the lid construction.
Now we come to the refractory. This stuff isn’t cheap though I was able to find a reputable
UK supplier with just a little internet browsing. So shop around folks!
Even so, to avoid waste, I filled the base with a dry mix up to the marked two inch line.
I checked the depth then poured the refractory into a bucket for mixing.
Add water very sparingly. You do NOT want a wet mix. Stir it well, a trowel works best,
and ensure there’s no dry spots. The finished mix should compact well but not be sodden.
The mixed content was poured back into the base and pounded down well. Cocoa my Labrador
took the opportunity to supervise my efforts… Pound it flat and level making sure there’s
no air gaps. Then wait ideally 24 hours. The next morning the base was nice and hard.
An old plastic paint can makes an ideal temporary mould liner. It leaves a good inch and a half
to two inch gap all around, which is ideal. The problem is the paint can wobbles slightly,
so I obviously didn’t do a brilliant job of flattening the refractory. I’ll see to that
shortly. I needed to cut a hole in the plastic paint
can to align my waste burner. Adding plenty of temporary weight held the can securely.
Remember the angle of the burner is important. As the can was plastic, I decided to cut the
hole nice and easily using my oil burner and a blow torch.
With careful placement, with just three or four passes I melted a hole just where I wanted
it. Remember the wobbly base? Our friend plasticine
(or play doe, modelling clay or whatever you want to call it) comes it really handy here.
Rolled into thin sausage shapes and pressed around the outer rim of the paint tin, this
will take out any wobble. I took a tiny amount of vegetable oil on a
paper tissue and rubbed this around the paint can. This should help act as a releasing agent.
You don’t need much as all. Just a sheen. I then wrapped cling film around the tip of
the oil burner. Again, keep this thin. Inside my shed, I secured everything in place.
The paint can rests snugly inside the base. The burner is pushed through at just the right
angle and this is secured firmly in place with a few clamps. Any kind of movement needs
restricting. You can see the burner sticking through there
at a nice angle. To avoid the refractory getting inside this, I packed plasticine around it.
Don’t push too hard or it will poke through the other side.
The plasticine stops the paint can wobbling and the refractory getting in, but the filling
process could easily dislodge everything. So I added several scoops of dry sand inside
the paint can. Its weight held everything firmly.
The lid was placed back on the paint can. You’ll see why in a moment.
More plasticine was added to the rear of the burner to prevent any refractory escaping.
This is a wonderful tip from Myfordboy. An ordinary electric sander becomes a fabulous
vibrating tool. I attached a piece of copper pipe to mine with a couple of screws. But
I found this wasn’t enough. With use the screws worked loose. I added a number of cable ties
and this seemed to do the trick. Mixing up the refractory again, this mix was
a little wetter than last time as it needs to move around more. But still, NOT TOO MUCH.
Only enough water to make it move. I’ve seen videos of people making a right
mess trying to fill this narrow slot on a foundry. The paint can lid makes this really
simple. Using a bit of old board and a scraper, just
push the refractory down the slot. Hardly any mess.
Pack the refractory down very well with a stick. Pay particular attention around the
burner as you’ll need to refractory to flow under the pipe. This is where the vibration
tool works wonders. No matter how much you pack it down with a stick, the vibration seem
to make it flow and sink so much more. Eventually the base was filled and this probably
uses more refractory than you’d expect. At this point a scrap of wood made an excellent
striking off tool to level off the refractory. The reinforced rim certainly came in useful.
Don’t rush this stage. Make sure you compact it as well as you can. Work out any air bubbles.
Fill any imperfections and tap out the air again.
When you’re happy, a light hand and a trowel make a nice job on the surface. See how the
repeated beating and vibrating has drawn the moisture upwards?
Now you can see the lid. You’ll notice I’ve screwed the handles down. This holds the structure
flat against a board preventing any unwanted curving and make things more controllable.
And with the lid filled, all we can do is wait for it to dry.
One week on and everything’s looking really good.
We need to take this can out as it’s too weak and won’t survive the heat of the foundry.
Lots and lots of tapping here. It took about 3 minutes of tapping and I gradually got harder
and harder and harder, but it wasn’t shifting. The refractory really grips well.
In the end I had no choice but to grab a pair of pliers.
The scraper removes any dried on material.
A few taps from the hammer help to loosen the lid from the board.
The board is just an old scrap piece. Don’t worry about the marks you’re about to see.
There we are… flip it over… looks quite good doesn’t it?
Now let’s look at the base. As you can see, that dried out a treat as
well. I didn’t to remove the paint can lid now and
hopefully the burner. That’s the right thing to do.
BUT I couldn’t get my burner out. I didn’t put enough cling film on. Please don’t make
the same mistake I did. So I had no choice but to smash the can out. Shame really. I
think it would have pulled out. The vegetable oil really did seem to do the trick.
It’s this pinching and twisting motion that you’ve got to do. It does work but you’ll
probably swear a lot if you have to do it the same way as I did.
Eventually it came free, but the burner is still in the bottom.
You can see the plasticine and a little bit of sand with we can tidy up in a moment.
Here you can see I’ve actually put the castors on to the base. Obviously we need a couple
of lockable ones to stop it from moving. There you go – I managed to get the burner
out. I had to use oil unfortunately which means I have a small oil stain inside my foundry
but other than that it’s not look too bad is it?
And here we have a finished product. I gave it a light sanding, applied some rust killer,
then gave it a few coats of heat resistant paint. All that’s needed now is the light
a small fire inside it to help it dry out properly before introducing it to proper foundry
heat. So I’m going to wrap things up there folks.
I hope you’ll agree with me that this is a nice easy build and you can expect good
things from this design of foundry and if you’ve got any questions, do get in touch.
If you enjoyed watching this video, please like it. If you didn’t like it, then why not
let me know why. I’m always eager to improve my videos.
Your comments and questions are always welcomed as I really love to hear from you so do drop
me a message below. Please do check out my YouTube channel and
of course my other videos. I’ve got about 40 videos out there now and I’m receiving
some fantastic feedback and I’m seeing a real interest from Subscriber, so thank you all
for that, and if you haven’t subscribed yet, please do.
If there’s a subject you’d like me to make a video on, let me know and I’ll do
my best to help. So that’s it for now folks, and thanks very
much for watching.