I’ve always had a fascination with sand casting and finally decided to just jump right into it. After taking the time to learn the basics I jumped right in. The first major hurtle to get over was making the foundry. If you haven’t already, feel free to check out the video I put together on how to build a propane heated foundry.
With the foundry out of the way, I now focused on making the pattern for my part. I made mine out of wood. The part I am casting will wind up as a miniature axe head made from brass….not for chopping, just for decoration. The pattern did not really take long since it is mainly just a tapered wedge.
These are some of the basic things I used for this project:
Here is the short video I put together covering this project:
I then focused on making my own green sand. Green sand is available for purchase but I wanted to try to make my own a first. I used THIS video tutorial to help with making my first batch of sand. Unfortunately, my sand did not come out very good but did work for my first casting.
I later wound up finding some good sand through a casting shop. They sold me a 5 gallon bucket of some really good stuff that worked much better than the first batch I made.
The flask is the part of the operation that actually receives the molten metal to make the part. It is basically a box that is made up of two halves. The top half is known as the “cope” and the bottom part is the “drag”. You can find these pre-made online but they’re easy enough to make on your own if youd rather go the DIY route.
An important thing to note about the flask is that the two halves need to come together perfectly flat without any spaces between them. I made mine from ¾” plywood and sanded them afterward to ensure they were nice and flat.
The other important feature of the flask is that you build in some kind of locating feature for the two halves so that they come together correctly every time. I built a simple male/female feature along the sides which worked really well. A dowel and socket approach would work also.
Here’s where the rubber meets the road. I placed my pattern for the axe head in the drag and cover it with green sand through a fine sifter. The part gets placed in the drag while it is in the upside down position. (once the cope is packed with sand it gets turned back over).
The first layer of sand around the pattern gets sifted so that the sand in contact with the pattern is as fine as possible. This will ensure the surface finish of the casted part is as fine as possible.
After sifting, I then packed the sand around the pattern. You’ll need to be careful to not move the pattern around during this step. After the first layer is good and packed in, I continued filling and packing until the drag is full of packed green sand.
With the pattern all packed into the drag, I turned it over to where it was right side up and get to see the back side of the pattern tightly held in place by the compacted sand. Im now looking at the top of the drag. The top of the drag gets a little bit of baby powder sprinkled on it to help with releasing the cope which is about to go on.
The cope now gets placed onto the drag and a sprue and riser are created. The sprue is the fill hole where the molten metal comes in and the riser is basically a vent to allow gasses to escape as the mold is filled. I used a short piece of aluminum tube (about .5” in diameter) for the sprue and a pencil for the riser.
Carefully holding the pencil and tube in place, I packed sand around them so they are held firmly in place and then gently removed them after the cope was completely full of packed sand. The cope and drag now get pulled apart and we are almost ready to pour some material into this little flask.
With the cope and drag separated, I cleaned up the holes just a bit from removing the pencil and the aluminum tube. Once I was happy with the shape of the two holes I set the cope aside for one last touch on the drag.
The drag still has the pattern in it and will need to be gently removed. I predrilled a small hole in the back of my wooden pattern (before beginning this process) so I could thread a wood screw in (by hand) and then carefully remove the pattern using the screw as a hand hold. After the pattern is removed, I carved in a couple of “gates”.
The gates are a just small veins in the green sand where the molten metal flows from the the molten brass to make it from the sprue to the pattern and vent. If you’re looking at the top of the drag where the part was just removed, you can see where the pencil and the aluminum tubing were in contacting the drag in the form of two small circular impressions. The gates get carved in the sand from these little impressions to the void in the sand where the pattern was held. They do not need to be very deep but it is best if they have nice smooth edges after they are carved in so take your time.
Time to heat up some material! With the cope and drag built up they get joined back together in the same orientation from when they were first put together. Obviously, this is to keep the sprue and the drag properly aligned. Now lets fire up that foundry : )
The foundry needs to heat up to operating temp before dropping in the brass material. With the crucible placed down in the foundry, I let my unit heat up until the crucible is a bright orange glow and then add in the brass. With a medium size crucible filled to the brim with chopped up brass door handles, it took about 30 minutes for the brass to become fully melted and ready to pour.
Now is a perfect time to address some safety concerns. If you are recreating this process, you are operating at your own risk so please be careful. Steel toe leather boots, jeans, leather gloves, long sleeve jacket, and a face shield are the bare minimum safety attire needed for this process. If you have some leather chaps, use those as well to better protect your legs. It’s best to perform this operation over dirt and not concrete. Concrete can pop and make tiny little explosions if it comes in contact with an 1800 degree crucible or molten brass. Again – please be very safe!
Back to the melting process. When the brass is fully melted, I sprinkled about 1/3 of a cup of boric acid (aka roach killer – found at the dollar store) in the crucible. The boric acid not only helps gather the slag but it also helps to prevent the zinc from burning out of the brass. After adding the boric acid, I waited about 5 more minutes and then got ready to remove the crucible and pour the material.
I broke up a cheap pair of stainless serving tongs and used one side as my scooping tool to remove the slag off the top of the melted brass. Moment of truth – time to remove the crucible and pour the brass.
Using a large pair of steel tongs, I lifted the crucible out of the foundry and slowly poured the brass into the sprue hole of the foundry until I saw the brass coming out of the vent hole. This lets me know that the entire pattern is full.
After carefully setting the crucible back in the foundry, I let the part cool in the flask for a second then opened the flask to find my completed part – how exciting is this! You can see the extra material from the sprue, gates, and vent are still attached and will need to be cut off. Other than that, I’d call this first part a complete success!
The final steps are pretty standard. I spent about an hour sanding and polishing this part and then added a small handle to it to complete this little miniature axe.
The handle is made from Red Grandis wood and is finished with boiled linseed oil.
I’ll say this is by far one of the most fun little projects I’ve done and has been a real eye opener for me. I cant stress the importance of good safety measures though…..as you can tell by now there are many safety risks working with melted material so please please please be safe!
All and all I am very happy with my miniature axe. If your are interested in purchasing one of these little gems, feel free to check them out HERE. Since these are custom made, the lead time may be longer than some of the more standard “stock” items.
Thanks for taking the time to learn more about this process. Be safe and take care – April.